The preparation and properties of polycrystalline Bi$_2$O$_2$Se -- pitfalls and difficulties with reproducibility and charge transport limiting parameters

Jan Zich; Tomáš Plecháček; Antonín Sojka; Petr Levinský; Jiří Navrátil; Pavlína Ruleová; Stanislav Šlang; Karel Knížek; Jiří Hejtmánek; Vojtěch Nečina; Čestmír Drašar

arXiv · 2504.15227

The preparation and properties of polycrystalline Bi$_2$O$_2$Se -- pitfalls and difficulties with reproducibility and charge transport limiting parameters

Jan Zich·Tomáš Plecháček·Antonín Sojka·Petr Levinský·Jiří Navrátil·Pavlína Ruleová·Stanislav Šlang·Karel Knížek·Jiří Hejtmánek·Vojtěch Nečina·Čestmír Drašar

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Abstract

Thermoelectric materials allow the direct conversion of waste heat into electricity, and novel materials are being investigated for this purpose. Recently, doped Bi$_2$O$_2$Se has shown high application potential. In this study, we discuss causes for large variation in reported transport properties of pure Bi$_2$O$_2$Se and present a preparation method that improves the reproducibility of undoped polycrystalline samples and improves their stability under thermal cycling. Key steps of this method include calcination of the Bi$_2$O$_3$ precursor, purification of the synthesized material in a temperature gradient, use of a coarse particle fraction and compaction of the powders in a Si3N4 die instead of a graphite die. The resulting polycrystalline material exhibits improved reproducibility and enhanced resistance to thermal cycling. It has room temperature electrical conductivity {\sigma}RT ~ 500 S.m-1 and Seebeck coefficient S ~ -300 $\mu$V.K$^{-1}$. These properties make it suitable as a reference material for future doping studies. The presented synthesis approach may provide a more reliable platform for investigating the intrinsic behavior and doping response of Bi$_2$O$_2$Se in thermoelectric applications.

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Jan Zich, Tomáš Plecháček, Antonín Sojka, Petr Levinský, Jiří Navrátil, Pavlína Ruleová, Stanislav Šlang, Karel Knížek, Jiří Hejtmánek, Vojtěch Nečina, Čestmír Drašar. 2025-04-21. The preparation and properties of polycrystalline Bi$_2$O$_2$Se -- pitfalls and difficulties with reproducibility and charge transport limiting parameters. https://arxiv.org/abs/2504.15227

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