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Nanostructures in metastable GeBi 2 Te 4 obtained by high-pressure synthesis and rapid quenching and their influence on physical properties

Nanostructures in metastable GeBi 2 Te 4 obtained by high-pressure synthesis and rapid quenching... We report on a new metastable modification of GeBi 2 Te 4 obtained by high-pressure high-temperature synthesis. It crystallizes in the CuPt type; different nanostructures are induced by various temperature programs under a constant pressure of 12 GPa. The particle size changes from <10 nm in quenched samples to >100 nm for melts slowly crystallized under high pressure. The smaller the domains the more random is their orientation distribution. The nanostructure has a high impact on the temperature characteristics of the electrical resistivity. The domain size determines whether the compounds are metallic or semiconducting. In the latter case the semiconducting behavior is due to the scattering of electrons at domain and/or grain boundaries. Intermediate behavior that starts off metal-like and changes to semiconducting at higher temperature has been observed for samples thermally quenched from the solid state at high pressure. Resistivity measurements of the high-pressure samples involving multiple heating and cooling sequences lead to a significant reduction of internal stress and finally approach a state which is characterized by ρ( T ) hysteresis. Our results show the large influence of the domain size and the grain boundary concentration on the properties of the materials and reveal how properties like the thermoelectric figure of merit ( Z T ) depend on the preparation technique. By the microstructuring of stable GeBi 2 Te 4 , the Z T value drops by one order of magnitude. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review B American Physical Society (APS)

Nanostructures in metastable GeBi 2 Te 4 obtained by high-pressure synthesis and rapid quenching and their influence on physical properties

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References (29)

Publisher
American Physical Society (APS)
Copyright
Copyright © 2011 The American Physical Society
ISSN
1098-0121
eISSN
1550-235X
DOI
10.1103/PhysRevB.84.184104
Publisher site
See Article on Publisher Site

Abstract

We report on a new metastable modification of GeBi 2 Te 4 obtained by high-pressure high-temperature synthesis. It crystallizes in the CuPt type; different nanostructures are induced by various temperature programs under a constant pressure of 12 GPa. The particle size changes from <10 nm in quenched samples to >100 nm for melts slowly crystallized under high pressure. The smaller the domains the more random is their orientation distribution. The nanostructure has a high impact on the temperature characteristics of the electrical resistivity. The domain size determines whether the compounds are metallic or semiconducting. In the latter case the semiconducting behavior is due to the scattering of electrons at domain and/or grain boundaries. Intermediate behavior that starts off metal-like and changes to semiconducting at higher temperature has been observed for samples thermally quenched from the solid state at high pressure. Resistivity measurements of the high-pressure samples involving multiple heating and cooling sequences lead to a significant reduction of internal stress and finally approach a state which is characterized by ρ( T ) hysteresis. Our results show the large influence of the domain size and the grain boundary concentration on the properties of the materials and reveal how properties like the thermoelectric figure of merit ( Z T ) depend on the preparation technique. By the microstructuring of stable GeBi 2 Te 4 , the Z T value drops by one order of magnitude.

Journal

Physical Review B – American Physical Society (APS)

Published: Nov 1, 2011

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