Operando X-ray scattering study of thermoelectric [beta]-[Zn.sub.4][Sb.sub.3]

• Published in: IUCrJ Vol. 7; no. 1
• Main Authors: Jorgensen, Lasse Rabol, Zeuthen, Christian Moeslund, Borup, Kasper Andersen, Roelsgaard, Ma, Broge, Nils Lau Nyborg, Beyer, Jonas, Iversen, Bo Brummerstedt, Fitch, A
• Format: Journal Article
• Language: English
• Published: International Union of Crystallography 01.01.2020
• Subjects: Occupancy; Powders (Particulate matter); X-ray diffraction
• ISSN: 2052-2525; 2052-2525
• DOI: 10.1107/S205225251901580X

The application of thermoelectrics for energy harvesting depends strongly on operational reliability and it is therefore desirable to investigate the structural integrity of materials under operating conditions. We have developed an operando setup capable of simultaneously measuring X-ray scattering data and electrical resistance on pellets subjected to electrical current. Here, operando investigations of [beta]-[Zn.sub.4][Sb.sub.3] are reported at current densities of 0.5, 1.14 and 2.3 A [mm.sup.-2]. At 0.5 A [mm.sup.-2] no sample decomposition is observed, but Rietveld refinements reveal increased zinc occupancy from the anode to the cathode demonstrating zinc migration under applied current. At 1.14 A [mm.sup.-2] [beta]-[Zn.sub.4][Sb.sub.3] decomposes into ZnSb, but pair distribution function analysis shows that [Zn.sub.2][Sb.sub.2] units are preserved during the decomposition. This identifies the mobile zinc in [beta]-[Zn.sub.4][Sb.sub.3] as the linkers between the [Zn.sub.2][Sb.sub.2] units. At 2.3 A [mm.sup.-2] severe Joule heating triggers transition into the [gamma]-[Zn.sub.4][Sb.sub.3] phase, which eventually decomposes into ZnSb, demonstrating Zn ion mobility also in [gamma]-[Zn.sub.4][Sb.sub.3] under electrical current. Keywords: thermoelectric materials; zinc antimonides; pair distribution function; operando study; powder X-ray diffraction; electrical resistance.