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Published January 2016 | Published
Journal Article Open

Apparent critical phenomena in the superionic phase transition of Cu_(2-x)Se

Abstract

The superionic phase transition of Cu_(2-x)Se accompanies drastic changes in transport properties. The Seebeck coefficient increases sharply while the electrical conductivity and thermal diffusivity drops. Such behavior has previously been attributed to critical phenomena under the assumption of a continuous phase transition. However, applying Landau's criteria suggests that the transition should be first order. Using the phase diagram that is consistent with a first order transition, we show that the observed transport properties and heat capacity curves can be accounted for and modeled with good agreement. The apparent critical phenomena is shown to be a result of compositional degree-of-freedom. Understanding of the phase transition allows to explain the enhancement in the thermoelectric figure-of-merit that is accompanied with the transition.

Additional Information

© 2016 IOP Publishing. Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 30 September 2015; Revised 17 November 2015; Accepted for Publication 16 December 2015; Published 11 January 2016. The authors thank Prof Peter W Voorhees for his insightful comments and ANSTO (Australia) for the provision of beam time. UA acknowledges the financial assistance from The Scientific and Technological Research Council of Turkey. The work conducted at Caltech was supported by the AFOSR MURI program under FA9550-12-1-0002. The work conducted at Northwestern University was supported by the Solid-State Solar-Thermal Energy Conversion Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (#DE-SC0001299).

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August 20, 2023
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