Effect of metal doping on the low-temperature structural behavior of thermo electric beta-Zn4Sb3
2007 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 180, no 9, 2603-2615 p.Article in journal (Refereed) Published
The low-temperature structural phase transitions of Bi, Pb, In and Sn-doped samples of thermoelectric Zn4Sb3 have been characterized on crystals grown from molten metal fluxes, using electrical resistance and single crystal X-ray diffraction measurements. Room temperature stable, disordered, beta-Zn4Sb3 undergoes two phase transitions at 254 and 235 K to the consecutively higher ordered phases a and alpha', respectively. The ideal crystallographic composition of alpha-Zn4Sb3 is Zn13Sb10. The alpha-alpha' transformation is triggered by a slight and homogenous Zn deficiency with respect to this composition and introduces a compositional modulation in the alpha-Zn4Sb3 structure. When preparing beta-Zn4Sb3 in the presence of metals with low melting points (Bi, Sn, In, Pb) the additional metal atoms are unavoidably incorporated in small concentrations (0.04-1.3 at%.) and act as dopants. This incorporation alters the subtle balance between Zn disorder and Zn deficiency in Zn4Sb3 and has dramatic consequences for its low-temperature structural behavior. From molten metal flux synthesis it is possible to obtain (doped) Zn4Sb3 samples which (1) only display a P-a transition, (2) only display a beta-alpha' transition, or (3) do not display any low-temperature phase transition at all. Case (2) provided diffraction data with a sufficient quality to obtain a structural model for highly complex, compositionally modulated, alpha'-Zn4Sb3. The crystallographic composition of this phase is Zn84Sb65.
Place, publisher, year, edition, pages
2007. Vol. 180, no 9, 2603-2615 p.
temperature polymorphism, Thermoelectric materials, zinc antimonides, order-disorder structural transitions, initio structure solution, thermoelectric properties, solid-solutions, phonon-glass, zn4sb3, zinc, transitions, stability, phases, figure
IdentifiersURN: urn:nbn:se:kth:diva-16963DOI: 10.1016/j.jssc.2007.07.013ISI: 000249591300026ScopusID: 2-s2.0-34548425737OAI: oai:DiVA.org:kth-16963DiVA: diva2:335006
QC 201005252010-08-052010-08-05Bibliographically approved