Academia.eduAcademia.edu

Figure 7 – uploaded by Terry Tritt

See full PDFdownloadDownload figure
FIG. 6. (Color online) Electrical transport properties for bulk materials. The temperature dependence of electrical transport properties for ZM, ZM-SPS, and MS-SPS samples: (a) electrical conductivity, (b) Seebeck coefficient, and (c) power factor.

Figure 6 (Color online) Electrical transport properties for bulk materials. The temperature dependence of electrical transport properties for ZM, ZM-SPS, and MS-SPS samples: (a) electrical conductivity, (b) Seebeck coefficient, and (c) power factor.

Related Figures (11)

FIG. 2. (Color online) (a) TEM image of the position near the contact surface. (b) Selected area ED pattern of (a). (c) HRTEM image of a single NC shown in (a). (d) TEM image of the free surface. [(e) and (f)] HRTEM images of coherent interfaces between dendrites shown in (d).
FIG. 2. (Color online) (a) TEM image of the position near the contact surface. (b) Selected area ED pattern of (a). (c) HRTEM image of a single NC shown in (a). (d) TEM image of the free surface. [(e) and (f)] HRTEM images of coherent interfaces between dendrites shown in (d).
FIG. 1. (Color online) (a) diagram of the MS process indicating the free surface (FS) and the contact surface (CS) of the resulting melt-spun ribbon is shown. (b) Image of melt-spun ribbons obtained under the processing described in the experimental section. (c) SEM photo of the ribbon’s contact surface. (d) SEM photo of the ribbon’s free surface.
FIG. 1. (Color online) (a) diagram of the MS process indicating the free surface (FS) and the contact surface (CS) of the resulting melt-spun ribbon is shown. (b) Image of melt-spun ribbons obtained under the processing described in the experimental section. (c) SEM photo of the ribbon’s contact surface. (d) SEM photo of the ribbon’s free surface.
FIG. 3. (Color online) HRTEM images of the ribbon’s cross section. (a) HRTEM image of the amorphous structure near the contact surface. (b) HRTEM image of the transition layer for amorphous crystallization. a,, a9, and b, are HRTEM images for marked regions: a, is for the amorphous structure, a, is for the nuclei, and b, is for the crystallization.
FIG. 3. (Color online) HRTEM images of the ribbon’s cross section. (a) HRTEM image of the amorphous structure near the contact surface. (b) HRTEM image of the transition layer for amorphous crystallization. a,, a9, and b, are HRTEM images for marked regions: a, is for the amorphous structure, a, is for the nuclei, and b, is for the crystallization.
FIG. 5. (Color online) Microstructure of ZM-SPS bulk materials. (a) TEM image of the grain boundary of ZM-SPS. (b) HRTEM image of the bound- ary between grain 6 and e of ZM-SPS. are composed of the Big52Sb;.4gTe3; compound with only a small deviation of that of the nominal composition. In fact, some nuclei are observed in the HRTEM image shown in Figs. 3(a) and 3(b) of the amorphous Big 5.Sb, 4gTe3. The SPS process enables the nuclei to grow into NC regions after nucleation and growth. However, owing to the rapid sinter- ing process, the amorphous structure cannot totally grow into NC or crystalline regions and therefore some levels of the amorphous structure are able to be preserved within the bulk material. Figures 4(b) and 4(c) show that in the bulk material there are 5—15 nm NC regions and certain grains with coher- ent interfaces. These observations indicate that the amor- phous structure, NC regions, and dendrites in the ribbons can be inherited in the bulk material after the SPS process. In order to compare with the MS-SPS sample, the microstruc- ture of the ZM-SPS sample is also observed by TEM and the TEM images of its microstructure are shown in Figs. 5(a) and 5(b). The fine microstructure of the boundary between grains 6 and e, as shown in Fig. 5(a), is more disorderly and unsystematic [Fig. 5(b)]. It indicates that the MS process can produce a special interface structure: coherent interfaces. The unique low-dimensional structures consisting of an amorphous structure, 5-15 nm fine NC regions, and coherent interfaces in the bulk material will most likely influence the electron and phonon transport properties to a significant ex- tent. The TEM images and microstructures that are shown in Figs. 2-4 are representative of a large number of TEM mi- crographs that were performed in elucidating the origin of
FIG. 5. (Color online) Microstructure of ZM-SPS bulk materials. (a) TEM image of the grain boundary of ZM-SPS. (b) HRTEM image of the bound- ary between grain 6 and e of ZM-SPS. are composed of the Big52Sb;.4gTe3; compound with only a small deviation of that of the nominal composition. In fact, some nuclei are observed in the HRTEM image shown in Figs. 3(a) and 3(b) of the amorphous Big 5.Sb, 4gTe3. The SPS process enables the nuclei to grow into NC regions after nucleation and growth. However, owing to the rapid sinter- ing process, the amorphous structure cannot totally grow into NC or crystalline regions and therefore some levels of the amorphous structure are able to be preserved within the bulk material. Figures 4(b) and 4(c) show that in the bulk material there are 5—15 nm NC regions and certain grains with coher- ent interfaces. These observations indicate that the amor- phous structure, NC regions, and dendrites in the ribbons can be inherited in the bulk material after the SPS process. In order to compare with the MS-SPS sample, the microstruc- ture of the ZM-SPS sample is also observed by TEM and the TEM images of its microstructure are shown in Figs. 5(a) and 5(b). The fine microstructure of the boundary between grains 6 and e, as shown in Fig. 5(a), is more disorderly and unsystematic [Fig. 5(b)]. It indicates that the MS process can produce a special interface structure: coherent interfaces. The unique low-dimensional structures consisting of an amorphous structure, 5-15 nm fine NC regions, and coherent interfaces in the bulk material will most likely influence the electron and phonon transport properties to a significant ex- tent. The TEM images and microstructures that are shown in Figs. 2-4 are representative of a large number of TEM mi- crographs that were performed in elucidating the origin of
FIG. 4. (Color online) Microstructure of MS-SPS bulk materials. (a) TEM image of MS-SPS. (b) HRTEM image of NCs surrounding amorphous struc- tures, blue circles in (a). (c) HRTEM image of NCs with coherent interfaces.
FIG. 4. (Color online) Microstructure of MS-SPS bulk materials. (a) TEM image of MS-SPS. (b) HRTEM image of NCs surrounding amorphous struc- tures, blue circles in (a). (c) HRTEM image of NCs with coherent interfaces.
FIG. 8. (Color online) Thermal transport properties for bulk materials. The temperature dependence of electrical and thermal transport properties for ZM, ZM-SPS, and MS-SPS samples: (a) total thermal conductivity and (b) lattice thermal conductivity. that of ZM-SPS (0.9 W m7! K7!). Since the electrical con- ductivity of the two (ZM-SPS and MS-SPS samples) are essentially the same, then this reduction is almost entirely due to a reduction in the lattice thermal conductivity. The lattice thermal conductivity «, of the ZM-SPS sample is al- most a factor of 2 lower than the x, of the ZM sample. These data are shown in Fig. 8(b), where the lattice thermal con- ductivity «, can be determined by the Wiedemann Frantz relation, k,=K-—LoT, where LoT is the electronic thermal conductivity «k,, L is the Lorentz number L=2.0
FIG. 8. (Color online) Thermal transport properties for bulk materials. The temperature dependence of electrical and thermal transport properties for ZM, ZM-SPS, and MS-SPS samples: (a) total thermal conductivity and (b) lattice thermal conductivity. that of ZM-SPS (0.9 W m7! K7!). Since the electrical con- ductivity of the two (ZM-SPS and MS-SPS samples) are essentially the same, then this reduction is almost entirely due to a reduction in the lattice thermal conductivity. The lattice thermal conductivity «, of the ZM-SPS sample is al- most a factor of 2 lower than the x, of the ZM sample. These data are shown in Fig. 8(b), where the lattice thermal con- ductivity «, can be determined by the Wiedemann Frantz relation, k,=K-—LoT, where LoT is the electronic thermal conductivity «k,, L is the Lorentz number L=2.0
FIG. 7. (Color online) The ratio of electrical conductivity and total thermal conductivity between 300 and 400 K.
FIG. 7. (Color online) The ratio of electrical conductivity and total thermal conductivity between 300 and 400 K.
FIG. 9. (Color online) The crystal structure of Bi,Te; and the calculated distances between plane Bi and Te.
FIG. 9. (Color online) The crystal structure of Bi,Te; and the calculated distances between plane Bi and Te.
FIG. 10. (Color online) The temperature dependence of the figure of merit ZT for ZM, ZM-SPS, and MS-SPS samples.
FIG. 10. (Color online) The temperature dependence of the figure of merit ZT for ZM, ZM-SPS, and MS-SPS samples.
FIG. 11. (Color online) The heat cycle dependence and thermal stability of the figures of merit ZT for the MS-SPS sample at different temperatures.
FIG. 11. (Color online) The heat cycle dependence and thermal stability of the figures of merit ZT for the MS-SPS sample at different temperatures.
Related topics:
EngineeringPowder MetallurgyMechanical AlloyingIon ImplantationSpark Plasma SinteringElectric ConductivityFigure of Merit
580 California St., Suite 400
San Francisco, CA, 94104
© 2025 Academia. All rights reserved