Low Temperature Structural and Property investigations in the Zn-Sb System

Sammanfattning: Thermoelectric Zn4Sb3 has a randomly disordered crystal structure at room temperature and undergoes a reversible sequence of phase transitions, ?-?-?’/?, at low temperatures. During the transformations interstitial Zn atoms and Zn vacancies present in the ?-phase become increasingly ordered. The low-temperature structures ? and ?’ can be described by differently stacked layers A (interstitial free) and B (containing five-atom Zn clusters).The Zn/Sb ratio can be slightly altered by small amounts of metal doping achieved by growing the crystals in a metal flux. The small doping amounts (< 1 at.%) have, however, a large impact on the structural low-temperature behavior. First principles calculations show ?-Zn4Sb3 to be thermodynamically stable because of the large entropy contribution from the disordered Zn substructure and that ordered ?-Zn4Sb3 is meatstable with respect to a decomposition into ZnSb and Sb. Resistivity, thermopower and charge carrier properties at low temperatures have been investigated for both binary and metal doped samples. Preliminary studies of the high pressure structural behavior of zinc antimonides have also been made. Both ZnSb and ?-Zn4Sb3 showed to be stable up to 8 GPa, which is in disagreement with earlier reports. Amorphous Zn41Sb59 could be produced at 8 GPa and temperatures between 350 and 550 oC in a multi anvil apparatus.