Bismuth Titanate

2D materials, which are self-supporting in large areas but are only a few atoms thick, are exciting considerable interest for potential applications as diverse as electronics, molecular filtration and structural materials. Ferroelectrics have many useful applications stemming from their electrically-switchable dielectric spontaneous polarizations, including in piezoelectric devices, nonvolatile memories and pyroelectric IR sensors. While 2D oxide materials are known, they have not yet received the same attention as materials such as graphene. Here we study the ferroelectricity in ultrasonically-exfoliated flakes of the layered Aurivillius oxide Bi5Ti3Fe0.5Co0.5O15 with a range of thicknesses. We show, for the first time, that ferroelectricity can exist in flakes with thicknesses of only 2.4nm, which is about one-half of the normal crystal unit cell. These flakes have relatively large areas (linear dimensions many times the film thickness), thus classifying them as 2D materials. Piezoresponse force microscopy (PFM) has been used to show that these very thin flakes both exhibit piezoelectric effects and that the ferroelectric polarization can be reversibly switched. A new model is presented that permits the accurate modelling of the field-on and field-off PFM timedomain and hysteresis loop responses from a ferroelectric during switching in the presence of charge injection, storage and decay through a Schottky barrier at the electrode-oxide interface. This allows the extraction of parameters such as the coercive fields (EC), electrostrictive coefficients (Q11) and spontaneous polarizations (PS) for the flakes. It is found that the values of PS are around 0.04(0.02)Cm -2 , and Q11=2(0.1)x10 -2 m 4 C -2 . These are in good agreement with other ferroelectric Aurivillius oxides. Ec scales with thickness (t), closely following the semi-empirical scaling law expected for ferroelectric materials, vis: 𝐸 𝐶 ∝ 𝑡 -2 3 . We believe this constitutes the first evidence for ferroelectricity in a 2D oxide material, and it offers the prospect of new devices that might use the useful properties associated with the switchable ferroelectric spontaneous polarization in a 2D materials format.

Lead-free (1x)Na 0.5 Bi 0.5 TiO 3 -xSrTiO 3 (NBT-STx; x = 0.05, 0.10, 0.15 and 0.20) ceramics were prepared using a hightemperature solid-state reaction method. X-ray diffraction patterns indicated that the ceramics were a cubic structure with space group Pm3m at room temperature. The average grain sizes slightly decreased with the increasing SrTiO 3 content observed by scanning electron microscope. The dielectric properties and complex impedance spectra were used to analyze the electrical behavior of the ceramics as a function of frequency at different temperature. The results showed that with the increase of x, the dielectric constant increased, however, the temperature of the dielectric maximum (T m ) and depolarization temperature (T d ) decreased. The modified Curie-Weiss law was used to describe the diffuseness behavior of the ceramics. The relaxation activation energy was estimated to be 2.32-2.73 eV through Arrhenius fitting, which indicated that the oxygen vacancy concentration in the samples was low.

Four piezoelectric transducers with aluminum nitride (AlN), zinc oxide (ZnO), and bismuth titanate (BiTi) as the active elements and two magnetostrictive transducers were fabricated with Remendur and Galfenol as the active elements. The irradiation was for 18 months with an integrated neutron fluence of approximately 8.68 × 10 20 n/cm 2 for E >1M e V , temperatures in excess of 420 °C, and a gamma fluence of 7.23 × 10 21 gamma/cm 2 . The sensor performance is explained in the context of the pulse-echo signals. The feasibility of ultrasonic transducers in a nuclear reactor has been established. This opens the door to leave-in-place sensors for in-reactor conditions and materials.

The influence of SrTiO3 addition on the microstructure and various electrical properties of (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNTBT6) ceramics, fabricated by a conventional high temperature solid state reaction, was investigated. Analysis of X-ray diffraction patterns revealed the formation of phase pure materials with tetragonal unit cell structure, tetragonality parameter c/a in the interval from 0.9940 to 1.0063 and crystallite sizes ranging from 33-76 nm for addition of 0.2 to 1 wt.%of SrTiO3. SEMstudies indicated that Sr2+ doping led to decrease in grain size and non-homogeneity of grain distribution for higher SrTiO3 amount (>0.6 wt.%). Complex impedance, modulus, and conductivity studies indicated the presence of grains and grain boundary contribution, non-Debye type of relaxation and NTCR behaviour of the test ceramic samples. Temperature dependent real part of complex permittivity showed peaks at 475?C and the dielectric loss tangent showed peaks corresponding to 125?C and 475...

Micro-Raman, SEM and electron nano-probe techniques are used to show that bismuth titanate thin films undergoes a local phase transformation from layered-perovskite structure to pyrochlore-like structure during filamentary electrical breakdown, with the loss of Bi and oxygen. In PZT, dendrite-like structures (precursors of electrical shorts) of a few microns diameter, produced by bipolar voltage cycling (i.e. fatigue), exhibit almost pure regions of α-PbO, β-PbO and rutile-TiO 2 . Note that β-PbO is not the stable ambient phase.

Indium oxide (IO) and indium tin oxide (ITO) are widely used in optoelectronics applications as a high quality transparent conducting oxide layer [1]. These coatings also are useful for enhancing the electrical properties of spacecraft thermal radiator coatings, where dissipating built-up static charge is crucial. In this work, we present the thickness-dependent electrical and optical properties of IO thin-films synthesized by ALD with the aim of finding the optimum condition for coating radiator pigments [2]. Trimethylindium and ozone were used as precursors for IO, while a tetrakis(dimethylamino)tin(IV) source was used for Sn doping to produce ITO. As-deposited IO films prepared at 140°C resulted in a growth per cycle of 0.46 Å/cycle and relatively low film resistivity.

Grain-oriented Nd-modified bismuth titanate (BNIT) ceramics with the a-b-plane perpendicular to the direction of magnetic field (MF) were successfully fabricated by applying MF-assisted forming at lower field strengths. A BNIT powder, in which 25% of the Bi 3+ -site were substituted with Nd 3+ , was synthesized by coprecipitation in an alkaline solution and successive calcination at 600°C. Green compacts of the BNIT powder were formed by applying various MF strengths (212 T) during slip casting and then sintered at 900 and 1000°C for different times. The cation substitution with Nd 3+ allowed very fine BNIT particles in a slurry to be magnetically aligned at lower field strengths. For BNIT ceramics sintered at 1000°C, the degree of grain orientation increased with increasing MF according to the parabolic relationship. Additionally, the grain orientation was enhanced by the preferential growth of anisotropic BNIT grains occurring at later stage of the sintering.

Grain-oriented Nd-modified bismuth titanate (BNIT) ceramics with the a-b-plane perpendicular to the direction of magnetic field (MF) were successfully fabricated by applying MF-assisted forming at lower field strengths. A BNIT powder, in which 25% of the Bi 3+ -site were substituted with Nd 3+ , was synthesized by coprecipitation in an alkaline solution and successive calcination at 600°C. Green compacts of the BNIT powder were formed by applying various MF strengths (212 T) during slip casting and then sintered at 900 and 1000°C for different times. The cation substitution with Nd 3+ allowed very fine BNIT particles in a slurry to be magnetically aligned at lower field strengths. For BNIT ceramics sintered at 1000°C, the degree of grain orientation increased with increasing MF according to the parabolic relationship. Additionally, the grain orientation was enhanced by the preferential growth of anisotropic BNIT grains occurring at later stage of the sintering.

Integrated (IUTs) and flexible ultrasonic transducers (FUTs) are presented for NDT at high temperatures. These transducers are made of sol-gel sprayed piezoelectric thick (> 40µm) ceramic films. The ceramic materials are lead-zirconate-titanate, bismuth titanate and lithium niobate which are for thickness measurement up to 150°C, 400°C and 800°C, respectively. The IUT can be also deposited onto one end of a long ultrasonic delay line to perform non-destructive testing at the other end at even higher temperatures. FUTs made of bismuth titanate films onto thin stainless steel foils are also used for thickness measurements at 300°C with a high temperature couplant sandwiched between the FUT and a steel substrate. All experiments at high temperatures were performed in pulse-echo and ultrasonic echoes with signal to noise ratios above 20dB were obtained. The centre operation frequencies of both IUTs and FUTs range from 4.4MHz to 10.7MHz.

Thick film piezoelectric ceramic sensors have been successfully deposited on different metallic substrates with different shapes by a sol-gel spray technique. The ball-milled bismuth titanate fine powders were dispersed into PZT solution to achieve the gel. The films with desired thickness up to 200 µm have been obtained through the multilayer coating approach. These thick films were also effectively coated onto thin sheet metals of thickness down to 25 µm. Self-support films with flat and shell geometries were made. Piezoelectricity was achieved using the corona discharge poling method. The area of the top silver paste electrode was also optimized. The center frequencies of ultrasonic signals generated by these films ranged from 3.6 to 30 MHz and their bandwidth was broad as well. The ultrasonic signals generated and received by these ultrasonic transducers (UTs) operated in the pulse/echo mode had a signal to noise ratio more than 30 dB. The main advantages of such sensors are that they (1) do not need couplant, (2) can serve as piezoelectric and UT, (3) can be coated onto curved surfaces and (4) can operate up to 440 • C. The capability of these thick film UTs for non-destructive evaluation of materials at 440 • C has been demonstrated.

Sodium bismuth titanate (Na 0.5 Bi 0.5 TiO 3 , abbreviated NBT) ceramics underwent concurrent successful synthesis on the basis of the hydrothermal method. A selected low-temperature process of thermal treatment was conducted to obtain a highly dense morphology, produced from high purity carbonates and oxides serving as initial precursors. The presence of well-crystallized NBT in the rhombohedral phase was also found at hydrothermal temperatures of 200 °C. X-ray diffraction (DRX), Raman spectroscopy, Infrared spectroscopy (IR), and Scanning electron microscopy (SEM) analysis enabled to verify the structure, phase, morphology, and composition of the used samples. NBT ceramics exhibit features specific to relaxor ferroelectrics, with a diffusion exponent γ of up to 1.5 to promote their applications in micro-electromechanical and energy harvesting systems. The photocatalytic behaviors of NBT powders have been assessed by means of the degradation of methylene blue (MB) through UV-light irradiation. The samples prepared with precursors having a Na/Bi ratio of 0.5/0.5 showed the highest methylene blue (MB) photodegradation rate of 100% under UV irradiation for 420 minutes. In addition, photocatalytic activities under different masses and pH values were discussed for the first time. In addition, the photocatalyst has excellent stability, due to the larger particle size and surface area, which opens up new possibilities for the design of multicomponent photocatalysts for future applications. The photocatalytic mechanism for the degradation of organic dyes (MB) has been principally assigned to the photoreduction process caused by superoxide radical anions ( • O 2-) and hydroxyl radicals ( • OH).

Pt/TiO2-Bi2O3 test catalysts were prepared by impregnating Pt on the sol-gel derived TiO2-Bi2O3 to give these testpieces high photocatalytic activity under visible light irradiation. The optimum Pt support content and TiO2 content were observed in the ranges 0.05-0.3 wt% and 17-28 wt%, respectively in the photocatalytic activity for Methylene Blue (MB) degradation on Pt/TiO2-Bi2O3. Specifically, those 0.1Pt/17TiO2-83Bi2O3, 0.2Pt/23TiO2-77Bi2O3 and 0.3Pt/28TiO2-72Bi2O3 samples showed relatively higher photocatalytic activity for the MB degradation. The results were closely related to (1) the restriction of recombination of the photo-induced electron and hole pairs by Pt, and (2) the presence of bismuth titanate with such high Ti content as built up by Pt.

at Arlington -Transition metal inclusion has enhanced photocatalytic activity of bismuth titanate (Bi2Ti2O7) up to an impurity threshold concentration. Beyond the threshold, spectral absorbance is continually red shifted but increased photocurrent is not reciprocated. We investigated, from first principles, the origin of decreased photocurrent in modified Bi2Ti2O7 (BTO) by calculating the electronic structures of a representative set of doping configurations and by performing a phase stability analysis of the doping. We report our theoretical/computational strategy of analyzing free energy space and show an explicit dependence of pure phase synthesis on changes in free energy. Also, we present a probability distribution of the doping configurations based on formation enthalpy to better understand the nature of doping in BTO. We found that transition metal substitutions are favorable at the A-sites due to unchanging coordination with O ions.

Pure (Bi 12 TiO 20 ) and La-and Pb-doped (Bi 12Àx La x TiO 20 e Bi 12Àx Pb x TiO 20 , with "x" up to 1.50) bismuth titanates were prepared by the oxidant peroxide method (OPM) and used for photodegradation of rhodamine b (RhB). The synthesized materials samples were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (DRS), X-ray photoluminescence (PL) spectroscopy, scanning electron microscopy (SEM), X-ray fluorescence (XRF) and N 2 physical adsorption. Rietveld refinements showed samples consisting mainly of sillenite structure with small amounts of a perovskite secondary phase in the La-and Pb-doped materials. The photocatalytic properties of all materials were evaluated by the discoloration of RhB solution under ultraviolet (UV) and visible irradiation, where the bismuth titanate obtained by the OPM route showed higher photocatalytic activity than the commercial TiO 2 . Furthermore, it was observed that the insertion of different ions in the bismuth titanate structure changes the band gap energy in different ways, which consequently altered the photocatalytic activities of the materials.

Bismuth titanate with sillenite structure (Bi 12 TiO 20 ) was prepared at lower temperatures and shorter times using a modified oxidant peroxide method (OPM). Bi 12 TiO 20 was synthesized utilizing commercial Bi 2 O 3 and reactive titanium dioxide nanoparticles having peroxo-modified surfaces. Rather than depending on particle size, the reaction mechanism is related to the highly exothermic decomposition of peroxo groups, regardless the titanium source used, which locally releases a large amount of energy that can accelerate the reaction, similar to self-propagating high temperature routes (SHS).

In this paper, we have successfully synthesized high quality single crystalline bismuth titanate with sillenite (Bi 12 TiO 20 ) phase by the oxidant peroxide method (OPM). The structures of precipitate and calcined materials were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (DRS), X-ray photoluminescence (PL) spectroscopy, thermogravimetry analysis (TG), differential scanning calorimetry (DSC) Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), scanning electron microscopy (SEM) and nitrogen adsorption/desorption. The XRD analysis showed that the calcination temperature of 500 1C and time of 1 h was found to be sufficient to produce Bi 12 TiO 20 powder and the DRS confirmed that the photoresponse of the prepared bismuth titanate extended to the visible light region at about 465 nm representing a possible photoactivity under solar irradiation. The photocatalytic activities were verified through the photocatalytic degradation of rhodamine b (RhB) as a model compound under visible light irradiation. It was found that the material calcined at 400 1C exhibits good photocatalytic activity compared to commercial TiO 2 , the kinetic rate constant over 400 1C is 0.006 min À 1 , which is 9.4 times higher than commercial TiO 2 . The higher photocatalytic activity of this material is mainly attributed to an increase in the extension of its optical absorption spectrum, as compared to TiO 2 .

Pure (Bi 12 TiO 20 ) and niobium-doped (Bi 12 Ti 1-x Nb x O 20 , with ''x'' up to 0.15) bismuth titanates were prepared by the oxidant peroxide method (OPM) and used to photodegradate rhodamine b (RhB) under UV and visible radiation. Rietveld refinements showed samples consisting mainly of sillenite structure with small amounts of a perovskite secondary phase in the Nb-doped materials. These bismuth-based catalysts exhibited superior performance than the commercial TiO 2 , with band gaps ranging from 2.53 of pure Bi 12 TiO 20 to 2.73 eV depending on the amount of niobium added, which seems to be responsible for the improved photoactivity of the doped catalysts under UV radiation.

We are reporting synthesis and structural and optical investigation of strontium bismuth titanate borosilicate glasses with addition of one mole percent cerium oxide (CeO2). Glasses were synthesized by conventional rapid melt quench method. XRD studies of the glass samples confirm the amorphous nature. Infrared absorption spectra various strontium bismuth titanate borosilicate glass samples having glass system 60[(Sr1-xBix)TiO3]-39[2SiO2B2O3]-1[CeO2] (x=0.0,0.1,0.2,0.4) were recorded over a continuous spectral range from 400 to 4000 cm−1. IR spectra were analyzed to determine and differentiate of various vibrational modes in the structural change. Raman spectroscopy of all glass samples was also carried out in the wave number range from 200 to 2000 cm−1.

Bismuth titanate (Bi4Ti3O12 - BIT) ceramics derived from different amounts of excess Bi2O3 were prepared using the polymeric precursor method. In spite of excess bismuth, single phase ceramics were obtained with a con?trolled microstructure. Raman analysis evidenced typical vibrational bands of the BIT phase. UV-vis spectra indicated that excess Bi2O3 causes a reduction in defects in the BIT lattice due to the suppression of oxygen vacancies located at the octahedral BO6-ion. The microstructure and electrical properties are strongly depen?dent on the excess Bi2O3. Appropriate initial Bi2O3 excess reduces the leakage current and loss tangent and thereby improves the polarization of BIT ceramics. Rietveld analyses confirmed that the powders crystallize in an orthorhombic structure with a space group of Fmmm at room temperature. The polarization reversal was investigated by applying ac voltage through a conductive tip during the area scanning and was investigated by piezoresponse force...

The film thickness dependence on the ferroelectric properties of lanthanum modified bismuth titanate Bi 3.25 La 0.75 Ti 3 O 12 was investigated. Films with thicknesses ranging from 230 to 404 nm were grown on platinum-coated silicon substrates by the polymeric precursor method. The internal strain is strongly influenced by the film thickness. The morphology of the film changes as the number of layers increases indicating a thickness dependent grain size. The leakage current, remanent polarization and drive voltage were also affected by the film thickness.

Calcium bismuth niobate (CaBi 2 Nb 2 O 9 , CBNO) thin films were evaluated for use as lead-free piezoelectric in micro-electromechanical systems. The films were grown by the polymeric precursor method on Pt/Ti/SiO 2 /Si (1 0 0) (Pt) substrates and annealed at 700 • C for 2 h in ambient and oxygen atmospheric conditions. The films were characterized by means of XRD, Raman, IR, PFM and electrical measurements. Annealing in ambient condition leads to improved ferroelectric properties, higher fatigue and retention resistances, and improved piezoelectric response. Furthermore, oxygen atmosphere produces bismuth vacancies (V Bi) that inhibit the movement of domain walls along the z-axis, and consequently reduces the piezoelectric coefficient. Independently of the applied electric field, the retained switchable polarization approached a nearly steady-state value after a retention time of 10 s.

We investigated the dielectric properties of pure and lanthanum modified bismuth titanate thin films obtained by the polymeric precursor method. X-ray diffraction of the film annealed at 300 • C for 2 h indicates a disordered structure. Lanthanum addition increases gradually the dielectric permittivity of films, keeping unchanged their loss tangent. From C-V curve we can see no hysteresis behavior indicating the absence of domain structure. The decrease in the conductivity for the heavily doped Bi 4 Ti 3 O 12 (BIT) must be associated to the unidentified crystal defects. For comparison, dielectric properties of crystalline BIT film were also investigated.

Effect of Ce and La substitution on the microstructure and dielectric properties of bismuth titanate (BT) ceramics was investigated. Bismuth titanate ceramics (Bi 4Àx A x Ti 3 O 12) (A = Ce or La; x = 0, 0.5, 1) were processed by sintering of pressed pellets, prepared from nanopowder synthesized by the modified sol-gel method. Pure and La modified bismuth titanate ceramics have single Bi 4 Ti 3 O 12 phase of Aurivillius type, whereas a small amount of Bi 2 Ti 2 O 7 pyrochlore phase appears in Ce modified bismuth titanate ceramics. In the same time addition of La and Ce improved sinterability of BT ceramics. The results of the measurement of dielectric constant and loss tangent at different frequencies (100 Hz-1 MHz) as a function of temperature reveal that Ce modified ceramics has a diffuse phase transition. Temperature T m , corresponding to the maximum value of the dielectric constant, is shifted to higher temperature and the maximum value of the dielectric constant is decreased with increasing frequency, which indicate that relaxor behavior is caused by Ce substitution.

CsPbI3, also known as cesium lead iodide, has garnered significant attention as a potential absorber in perovskite solar cells (PSCs). CsPbI3-PSCs have not matched the high performance of hybrid PSCs. This study aimed to identify an effective combination of charge transport layers. Six-hole transporting layers (HTLs) including Spiro-OMeTAD, Cu2O, CuO, CuAlO2, CuSbS2, and SrCu2O2, as well as five electron transporting layers (ETLs) such as TiO2,WO3, ZnO, IGZO, and CdZnS, were tested
separately in 30 PSCs. The findings of this research indicate that CuAlO2 as the HTL andWO3 as the ETL that are the most appropriate materials among the options examined, so we use FTO/WO3/CsPbI3/CuAlO2/Au as a required PSC. In this research, we used SCAPS (Solar Cell Capacitance Simulator)−1D device modeling to investigate the bilayer ETL of inorganic CsPbI3-PSC and discover the methods to improve their efficiency. In planar PSCs, optimizing electron–hole pair extraction and recombination at the ETL/perovskite interface is crucial for achieving high performance. The key concept is to enhance theWO3/perovskite interface properties by adding a 5 nmultra-thin layer (UTL) of C60. The bilayer structureWO3/C60 was found to have the advantage of high electron extraction and low interfacial recombination, primarily due to more effective energy level alignment and defect passivation. To achieve the superior efficiency of PSC, various factors such
as defect and doping densities in all layers, the energy level alteration of ETL and HTL, interface defect densities on both ETL and HTL sides, back metal contact, operating temperature, and parasitic resistances were optimized. After optimizing these parameters, the efficiency of the system containing WO3/C60 bilayer ETL was found to be 29.39%. The current work proposes a straightforward and promising method to create photovoltaic devices, especially for many types of perovskites, with
desirable charge transport layers and recombination properties.

In this work, multilayered bismuth titanate ceramic tapes engineered by combining aqueous tape casting and laminating process were produced. The structural and dielectric properties of green and sintered multilayered materials, with 1 to 5 layers, were explored. Diffraction peaks related to the bismuth titanate phase of structure Bi 4 Ti 3 O 12 were identified in the precursor powder and the green and the sintered tapes. In addition, a Bi 2 Ti 2 O 7 structure phase was indexed to the sintered tape. Modifications of the dielectric behavior with the increase in the number of layers composing the samples and with the sintering procedure were observed. Considering the green multilayered BIT ceramics, values between 10 and 14 as a function of the distinct number of layer were found at 1.0 GHz. On the other hand, for the sintered BIT multilayered, values between 2.3 and 8.5 in a wide frequency range were observed, showing a constant behavior as a function of the

The development of new safe inorganic UV filters to effectively protect the skin from ultraviolet (UV) radiation effects is an emerging issue. Bismuth titanate-based UV filters embedded into mesoporous silica nanoparticles (MSN) represent a new class of inorganic sunscreens, with excellent UVA and UVB shielding properties. In addition, the presence of bismuth ions promotes a self-sealing process, allowing (i) the entrapment of the active phases in the deepest core of the system and (ii) the formation of an external glassy silica layer with a consequent suppression of the photocatalytic activity. In this work, aimed at studying in detail the self-sealing mechanism and accessing the role of bismuth ions in the formation of the system, a series of samples impregnated with a different amount of bismuth were investigated. The self-sealing process already occurs at the lowest content of bismuth and the mechanism is demonstrated to be triggered by the ability of Bi to work as a low-melting point agent for silica. Finally, a sunscreen formulation containing the new UV filter was prepared and the Sun Protection Factor (SPF), the pH and the viscosity were measured, demonstrating the potential of the proposed material for large-scale applications.

Lead bismuth titanate ceramics were prepared using solid-state method. The structural and dielectric behaviors were studied using X-ray diffraction, scanning electron microscopy, and LCR meter. X-ray diffraction studies showed that crystal structure changed with changing compositions and sintering temperatures. The value of dielectric constant was found to be more for leadfree samples with the addition of 1 mol% Fe 2 O 3 rather than CrO 3-doped samples. Activation energy, E a, was determined from the slope of log s versus 1000/T plots for ceramic samples 3P7BT1C800 and 3P7BT1C900. Impedance spectroscopy revealed that resistance decreases with increasing temperature.

Mild agate mortar activation followed by sintering of precursors, in resemblance to modified solid state process, was studied for synthesis of the aurivillius bismuth titanate. Hand on mill activation was carried out for eight hours followed by annealing treatment at 1000°C for 12 hours in presence of air atmosphere to obtain the proper phase. Scherrer’s formula was utilized to estimate crystallite size along with planes of orientation. Crystallite size was about 65nm while prominent peaks of orientations were (-117), (006), (111), (200) and others. FESEM and TEM studies were carried to obtain the morphology and estimated grain size of the synthesized aurivillius compound. Morphological features execute the material system to be nanocrystalline in nature as estimated from grain size measurement in correspondence with XRD crystallite size estimation. FTIR analysis confirms M-O coordinations of synthesized modified perovskite (aurivillius) sample. Optical property was evaluated from U...

Electric and dielectric properties of silver phosphate glass of the composition (NH 4 H 2 PO 4) 1−x (AgNO 3) 1−x (AgI) x (x = 0, 0.05, 0.10, 0.15, 0.20 and 0.25) were characterised using impedance spectroscopy. Samples were synthesized using the conventional melt quenching method. A decrease in the bulk resistance of the samples was observed with either increasing the temperature and/or dopant concentration, which indicates a semi-conducting behaviour with thermal activation conduction mechanism. In addition, the relaxation peak was observed to shift towards higher frequency with increasing temperature or dopant concentration. The slight asymmetrical shape of the relaxation peak together with the presence of the centre of the semicircle in Nyquist plot below the real axis indicate a non-Debye relaxation type. Electrical conductivity was found to switch from DC-conductivity to AC-conductivity at a certain frequency (crossover frequency). The crossover activation energy showed an inverse proportion with dopant concentration. The material was observed to follow Jonscher's power law, where the values of the power law exponent were found to decrease with increasing temperature. This behaviour indicates that the dominant conduction mechanism can be well-explained in terms of the Correlated Barrier Hopping (CBH) model. The activation energy and the hopping energy were found to decrease with increasing AgI-dopant level, indicating an enhancement in the electrical conductivity of the samples.

In this work, a new photocatalyst based on bismuth titanates with outstanding visible photocatalytic activity was prepared by a facile hydrothermal method. The synthesised material showed visible activity as high as UV activity of commercial TiO 2 P25 under the same experimental conditions for phenol degradation. A wide characterisation of the photocatalyst was performed. The material was composed of three phases; majority of Bi 20 TiO 32 closely interconnected to Bi 4 Ti 3 O 12 and amorphous TiO 2. The high visible activity showed by this material could be ascribed to a combination of several features; i.e. low band gap energy value (2.1 eV), a structure allowing a good separation path for visible photogenerated electron-holes pairs and a relatively high surface area. This photocatalyst appeared as a promising material for solar and visible applications of photocatalysis.

New photocatalysts based on bismuth titanates doped with iron with outstanding visible photocatalytic activity were prepared by a facile hydrothermal method followed by incipient wetness impregnation. The starting material was composed by three phases; majority of Bi 20 TiO 32 closely interconnected to Bi 4 Ti 3 O 12 and amorphous TiO 2. Fe doping increased the already very high visible activity of the original material. The high visible activity showed by these materials could be ascribed to a combination of several features; i.e. low band gap energy value (as low as 1.78 eV), a structure allowing a good separation path for visible photogenerated electron-holes pairs and a relatively high surface area. Fe doping could be acting as bonding paths for the bismuth titanates phases, and the amount of Fe on the surface was found to be a crucial parameter on the photocatalytic activity of the materials. Visible activity of the best photocatalyst was superior to UV-Activity of commercial TiO 2 P25 used as reference in same experimental conditions.

New photocatalysts based on bismuth titanates doped with iron with outstanding visible photocatalytic activity were prepared by a facile hydrothermal method followed by incipient wetness impregnation. The starting material was composed by three phases; majority of Bi 20 TiO 32 closely interconnected to Bi 4 Ti 3 O 12 and amorphous TiO 2. Fe doping increased the already very high visible activity of the original material. The high visible activity showed by these materials could be ascribed to a combination of several features; i.e. low band gap energy value (as low as 1.78 eV), a structure allowing a good separation path for visible photogenerated electron-holes pairs and a relatively high surface area. Fe doping could be acting as bonding paths for the bismuth titanates phases, and the amount of Fe on the surface was found to be a crucial parameter on the photocatalytic activity of the materials. Visible activity of the best photocatalyst was superior to UV-Activity of commercial TiO 2 P25 used as reference in same experimental conditions.

In this work, a new photocatalyst based on bismuth titanates with outstanding visible photocatalytic activity was prepared by a facile hydrothermal method. The synthesised material showed visible activity as high as UV activity of commercial TiO 2 P25 under the same experimental conditions for phenol degradation. A wide characterisation of the photocatalyst was performed. The material was composed of three phases; majority of Bi 20 TiO 32 closely interconnected to Bi 4 Ti 3 O 12 and amorphous TiO 2. The high visible activity showed by this material could be ascribed to a combination of several features; i.e. low band gap energy value (2.1 eV), a structure allowing a good separation path for visible photogenerated electron-holes pairs and a relatively high surface area. This photocatalyst appeared as a promising material for solar and visible applications of photocatalysis.

Several strategies have been employed to tune the functional properties of environmentally friendly Barium titanate (BaTiO3). In this work, bismuth (Bi) doped BaTiO3 with a general formula Ba1-xBi2x/3TiO3 (where x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06) were prepared by the conventional solid-state reaction method. The effect of Bi on the structure of BaTiO3; and their morphological and compositional studies were carried out by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) respectively. Furthermore, the effect of Bi on the transport properties of BaTiO3 was investigated. Our studies revealed that for x = 0.01, Bi doping gives rise to the highest tetragonality of the crystal with more homogeneous grains and pores distribution among all the doping concentration. Furthermore, the dielectric constant for x = 0.01 samples has been observed to be the highest, which is consistent with the structural and morphological studies. Also, th...

Substitution of both isovalent and aliovalent cations for the host ones in perovskite lattice plays a very important role in these modification mechanism. The polycrystalline (Bi 0.5 Na 0.5)Zr 0.08 Ti 0.92 O 3 (BNZT) ferroelectric thin films were deposited by using CBD method. XRD analysis revealed a rhombohedral perovskite type structure with lattice constants a=b=c=3.790Å and α=89.65°. The morphological and dielectric studies have been also made.

Substitution of both isovalent and aliovalent cations for the host ones in perovskite lattice plays a very important role in these modification mechanism. The polycrystalline (Bi 0.5 Na 0.5)Zr 0.08 Ti 0.92 O 3 (BNZT) ferroelectric thin films were deposited by using CBD method. XRD analysis revealed a rhombohedral perovskite type structure with lattice constants a=b=c=3.790Å and α=89.65°. The morphological and dielectric studies have been also made.

Bismuth-deficient sodium bismuth titanate (nominally Na 0.5 Bi 0.49 TiO 2.985 , NB 0.49 T) is a good oxide-ion conductor. Here we report the influence of A-site divalent ions, M 2+ = Ca 2+ , Sr 2+ and Ba 2+ , on the electrical properties of NB 0.49 T. A-site divalent doping for Bi 3+ enhances the bulk (grain) conductivity by~one order of magnitude without changing the conduction mechanism, which is attributed to an increase in the oxygen vacancy concentration based on the doping mechanism Bi 3+ + ½ O 2− → M 2+. Among these three dopants, Sr 2+ is the most effective in increasing the bulk conductivity due to a combination of its smaller mismatch in ion size with Bi 3+ , its intermediate polarisability and lower bond strength to oxygen compared to Ca 2+ and Ba 2+. Doping strategies for further improvements to bulk conductivity of NBT materials are discussed based on these results. Comparison with other oxide-ion conductors and initial stability test under reducing atmosphere show the doped non-stoichiometric NBT materials are promising for low and intermediate temperature applications.

The preparation of high-density lead-free potassium-bismuth titanate K 0.5 Bi 0.5 TiO 3 about 96-98% of the calculated density (X-ray), confirmed by the Archimedes method, is presented. All stages of the technological process are explained in detail. The control of microstructure was performed by scanning electron microscopy. The crystal structure and phase content of samples were determined by X-ray diffraction at each stage of sintering. Four types of samples were obtained under various technological conditions. The ultrasonic measurements of the obtained samples were carried out and basic parameters were determined, such as Young and Kirchoff modulus and Poisson's ratio were determined at room temperature. The dielectric measurements show that the maximum value of dielectric permittivity is shifted towards higher temperatures as the frequency increases. This feature is characteristic of ferroelectric relaxor materials. The presented materials can be a good starting point for the development of lead-free ceramics.

We are reporting synthesis and structural and optical investigation of strontium bismuth titanate borosilicate glasses with addition of one mole percent cerium oxide (CeO2). Glasses were synthesized by conventional rapid melt quench method. XRD studies of the glass samples confirm the amorphous nature. Infrared absorption spectra various strontium bismuth titanate borosilicate glass samples having glass system 60[(Sr1-xBix)TiO3]-39[2SiO2B2O3]-1[CeO2] (x=0.0,0.1,0.2,0.4) were recorded over a continuous spectral range from 400 to 4000 cm−1. IR spectra were analyzed to determine and differentiate of various vibrational modes in the structural change. Raman spectroscopy of all glass samples was also carried out in the wave number range from 200 to 2000 cm−1.

A new series of lead bismuth titanate borosilicate glasses with addition of one percent lanthanum oxide have been synthesized using melt-quench technique. X-ray diffraction patterns have been recorded to confirm the amorphous nature of the prepared glass samples. The synthesized glasses have been characterized by using various spectroscopic techniques such as UV-visible, infrared, and Raman spectroscopy. UV-visible measurements were recorded in the wavelength range from 200 to 1100 nm whereas IR and Raman spectroscopic measurements were recorded over a continuous wavenumber range from 400 to 5000 cm−1 and 1000 to 2000 cm−1 respectively. The different absorption peaks/bands were formed in IR spectral patterns. The spectral bands appear towards the lower wavenumber sides due to the Bi and Pb, content while the bands appear towards the higher wavenumber sides due to the formation of diborate and triborate network units.

Strontium bismuth titanate (SrBi 4 Ti 4 O 15) thin films were deposited on (111) Pt/Ti/SiO 2 /Si substrates by spin coating from the polymeric precursor method. Annealing in static air and dynamic oxygen atmosphere was performed at 700 C for 2 h. The films were characterized by X-ray diffraction, atomic force microscopy and electric properties. The dielectric properties of SrBi 4 Ti 4 O 15 films were found to be remarkably sensitive to the annealing atmosphere. The CeV characteristics of the metal-ferroelectric metal structure showed a typical butterfly loop that confirms the ferroelectric properties of the film related to the domains switching. SrBi 4 Ti 4 O 15 thin films annealed in oxygen atmosphere showed lower ferroelectric behavior indicating a weak ferroelectricity along c-axis direction.

Bismuth titanate (Bi 4 Ti 3 O 12-BIT) films were evaluated for use as lead-free piezoelectric thin-films in micro-electromechanical systems. The films were grown by the polymeric precursor method on Pt/Ti/SiO 2 /Si (1 0 0) (Pt) bottom electrodes at 700 8C for 2 h in static air and oxygen atmospheres. The domain structure was investigated by piezoresponse force microscopy (PFM). Annealing in static air leads to better ferroelectric properties, higher remanent polarization, lower drive voltages and higher piezoelectric coefficient. On the other hand, oxygen atmosphere favors the imprint phenomenon and reduces the piezoelectric coefficient dramatically. Impedance data, represented by means of Nyquist diagrams, show a dramatic increase in the resistivity for the films annealed in static air atmopshere.

Bismuth titanates are of great technological interest because of their applications as nonvolatile ferroelectric memories, and high-temperature piezoelectric materials. All of them belong to the Aurivillius bismuth layer-structure. Some compounds belonging to that family show high-conduction behaviour, which difficult the poling process. On the contrary, the Calcium Bismuth Titanates have shown very high resistivity values, which make suitable the poling process at relatively high temperatures, necessary for a correct polarization step. Compounds of the following composition: Ca x Bi 4 Ti 3+x O 12+3x , (x=1,2), has been synthesized by solid-state reaction between the corresponding oxides and carbonates. Lattice parameters, Structure crystalline, and Space Group have been established by XRD techniques. Sintering of isopressed compacts has been studied by Dilatometer tests. High-density bodies have been obtained at relatively low temperature. Curie temperature, T C , Room Temperature permittivity, conductivity as a function of temperature and piezoelectric parameters have been measured on sintered, well-densified samples. The results seem to indicate that these compounds are very promising piezoelectric materials for high-temperature applications.

The effect of modifying the properties of KNN-based ceramics with Bi 2 Ti 2 O 7 (BiT) been investigated in this work. The density measurements show that additions of BiT to the samples slightly increase the density values. Scanning electron microscope images of the samples indicate that the average sizes of the grains decrease with BiT addition while the volume of pores increase. X-ray diffraction results show that for (K 0.5 Na 0.5)NbO 3 based samples, a transformation from orthorhombic to pseudo-cubic phase is observed. For both K 0.48 Na 0.48 Li 0.04)(Nb 0.9 Ta 0.1)O 3 and K 0.48 Na 0.48 Li 0.04)(Nb 0.86 Ta 0.1 Sb 0.04)O 3-based compositions, the phase transition is from an orthorhombic-tetragonal coexistence to a tetragonal structure dominated phase coexistence. The dielectric constant, dielectric loss and resistivity values of the samples increase slightly with BiT addition. Good hysteresis curves are obtained in (K 0.5 Na 0.5)NbO 3-based samples only at low BiT amounts. Remnant polarization values between 9 C/cm 2 and 25 C/cm 2 are obtained for K 0.48 Na 0.48 Li 0.04)(Nb 0.9 Ta 0.1)O 3 and K 0.48 Na 0.48 Li 0.04)(Nb 0.86 Ta 0.1 Sb 0.04)O 3-based samples. With the exception of KNNLT samples where the d * 33 values increase from 203 ± 7 pm/V at 0 mol% to 275 ± 6 pm/V at 0.35 mol%, the d * 33 values of the samples gradually decrease with increasing BiT content. This work shows that to obtain good properties for KNN-based ceramics, only very small amounts of BiT are required.

Lead-free ferroelectric ceramics with 2 different compositions were produced using the mixed-oxide synthesis route. The electro-mechanical properties of samples doped with potassium sodium niobate (KNN) compositions of (K 0.44 Na 0.52 Li 0.04)(Nb 0.86 Ta 0.10 Sb 0.04)O 3 and (K 0.43 Na 0.53 Li 0.04)(Nb 0.84 Ta 0.10 Sb 0.06)O 3 were characterized using the single edge V-notch beam method of fracture toughness determination and hysteresis measurements. Compositional analysis using X-ray fluorescence showed similar elemental amounts between the expected and actual values. From the controlled crack growth of notched bars in four-point bending, the fracture toughness was found to be 1.13 70.11 MPa m 1/2 for composition 1 and 0.92 70.12 MPa m 1/2 for composition 2. The calculated high signal piezoelectric charge coefficient d ′ 33 values for composition 1 is 470738 pm/V and is 397 7 30 pm/V for composition 2. The remnant strain varied between both compositions from 0.0003 to 0.0019. The results show that slight modifications in the amounts of the same elements in a ferroelectric ceramic have very little effect on the properties.