Is SrZn2Sb2 a Realistic Candidate for High-Temperature Thermoelectric Applications?

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The structure and thermal stability of thermoelectric (TE) SrZn2Sb2 have been probed by means of both in situ and ex situ powder X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetry, and inductively coupled plasma optical emission spectrometry. Densification of the sample during synthesis induced evolution of an increasing degree of impurity phases coming from the decomposition of SrZn2Sb2. Variable-temperature synchrotron powder X-ray diffraction experiments performed on an air-packed sample revealed a structural breakdown occurring between 500 and 600 K. DSC performed in an argon flow revealed the decomposition to be an exothermic and kinetically slow transition accompanied by a weight loss of zinc, showing the extent of decomposition to increase as a function of decreasing heating rate applied in the DSC experiments. Using the Kissinger and Ozawa analysis methods, activation energies of ≈1.9 eV were obtained. After five days at 850 K in vacuum, argon, and air atmospheres, cold-pressed samples showed a complete depletion of SrZn2Sb2, however, the zinc evaporation was strongly inhibited compared to the DSC experiments, which is likely to be because of the reduced surface area. These observations indicate that the structural decomposition is independent of both operating atmosphere and surface-to-volume ratio, making SrZn2Sb2 unsuitable for practical TE applications in intermediate- and high-temperature environments in spite of the promising TE properties reported previously.

Original languageEnglish
JournalJournal of Physical Chemistry C
Pages (from-to)5317-5324
Number of pages8
Publication statusPublished - 15 Mar 2018

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