Operando X-ray scattering study of segmented thermoelectric Zn4Sb3

Peter Skjøtt Thorup, Rasmus Stubkjær Christensen, Martin Roelsgaard, Bo Brummerstedt Iversen*

*Corresponding author af dette arbejde

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avisTidsskriftartikelForskningpeer review

Abstract

The inexpensive and high-performing thermoelectric material β-Zn 4Sb 3 is a mixed ionic-electronic conductor, which suffers from stability issues due to Zn migration in the structure under thermoelectric operating conditions. Previous ex situ studies have shown that ion migration in β-Zn 4Sb 3 and Cu 2Se can be reduced in segmented modules, where ion-blocking interfaces increase the critical voltage across the module before metallic whiskers are observed at the surface. Here, we use spatially resolved operando X-ray scattering measurements across the pellet coupled with electrical resistivity measurements to examine the stability improvement obtained in segmented β-Zn 4Sb 3 pellets with ion-blocking steel interfaces under thermoelectric operating conditions. Quantitative phase analysis shows that β-Zn 4Sb 3 decomposes into ZnSb and Zn, but the rate is significantly reduced in segmented pellets compared with unsegmented pellets. The greatest improvement is found under the mildest conditions investigated, with a hot side temperature of 250 °C and an applied current density of 0.5 A mm −2. Microstructure analysis by scanning electron microscopy and energy dispersive X-ray spectroscopy after stability tests reveals a Zn phase front during migration, as well as residual β-Zn 4Sb 3 islands trapped inside the decomposed ZnSb phase. Overall, the operando approach provides a dynamic atomic structure basis for the effect of segmentation on the stability of β-Zn 4Sb 3 under thermoelectric working conditions.

OriginalsprogEngelsk
TidsskriftJournal of Materials Chemistry A
Vol/bind11
Nummer11
Sider (fra-til)5819-5829
Antal sider11
ISSN2050-7488
DOI
StatusUdgivet - feb. 2023

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