Anionic high-temperature conduction in single crystals of nonstoichiometric phases R1 − yMyF3 − y (R = La-Lu, M = Ca, Sr, Ba) with the tysonite (LaF3) structure
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- Sorokin, N.I. & Sobolev, B.P. Russ J Electrochem (2007) 43: 398. doi:10.1134/S1023193507040064
Electrophysical properties of single crystals of nonstoichiometric phases R1 − yMyF3 − y, where R = La-Lu, M = Ca, Sr, or Ba, with the tysonite (LaF3) structure, which are present in a metastable state after being grown and cooled, are measured in the temperature interval extending from 300 to 1073 K. It is discovered that, during a sufficiently long high-temperature investigation, solid solutions R1 − yCayF3 − y, where R = Tb, Dy, or Ho, undergo irreversible variations in the phase composition in the temperature region 723 to 823 K. This level of temperatures, which correspond to partial decomposition of phases R1 − yCayF3 − y with the rare-earth elements of the end of the period, lies above the temperatures to which the fluoride solid electrolytes are usually heated when used in solid-state electrochemical devices. The temperature and concentration dependences of the phases’ electroconduction are explained in the framework of the vacancy mechanism of anionic transport.