Ultra-Low Thermal Conductivity in Semiconducting High Entropy Oxide, AWO₄

High entropy oxides (HEOs) have recently gained a great deal of attention for their enhanced thermal properties. However, one of the biggest limitations for these systems has been low electrical conductivity; limiting their potential as thermoelectrics[1-4]. Recently, a new HEO, (Mn,Fe,Co,Ni,Cu,Zn)WO₄ (AWO₄), was reported where the high configurational entropy drove the material from an insulating to a semiconducting state[5]. Improved thermal properties combined with its semiconducting behavior makes AWO₄ ideal for studying the behavior of thermal conductivity in a first of its kind, phonon-glass electron-crystal HEO system. Further, if these properties persist over a wide temperature range, then the material has potential for use in industrial applications. In this talk, we report ultra-low thermal conductivity in semiconducting AWO₄ over a wide temperature range. We observe a substantial suppression of thermal conductivity as compared to the parent phases due to increased defect scattering and compare these results with theoretical predictions. We also report magnetothermal conductivity of AWO₄ showing at high temperatures a suppression of the electronic contribution to thermal conductivity under applied B field and at low temperature an enhancement of the phonon contribution due to reduced phonon-magnon scattering.

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5. Katzbaer, Rowan R., et al. Inorganic Chemistry (2023).