Conductivity and Hydration of Fluorite-Type
La_6xWO_121.5x Phases (x = 0.4; 0.6; 0.8; 1)

G. S. Partin, D. V. Korona^z, A. Ya. Neiman^†, and K. G. Belova

Ural Federal University Named after the First President of Russia B.N. Eltsin,
ul. Mira 19, Ekaterinburg, 620002 Russia

Received July 22, 2014

Abstract—Solid-phase synthesis was used to obtain four phases from the region of cubic fluorite-type
La₆WO₁₂–La₁₀W₂O₂₁ (La₅WO_10.5) solid solution. The temperature dependence of conductivity was measured
using the impedance spectroscopy technique in the atmosphere of dry ( = 10^–4 atm) and humid ( = 3
10^–2 atm) air and also when was varied from 0.21 to 10^–20 atm. Ionic transport numbers t (ion) are calcu-
lated (0.6 to 0.9). It was shown that the La_5.6WO_11.4 phase had a relatively high stability towards hydrolysis, as
the value of its conductivity dropped negligibly (as compared to other studied samples) after long–term sample
conditioning in a humid atmosphere. Activation energies of hole (0.85 to 0.98 eV) and proton (0.49to 0.56 eV)
conductivity were calculated. The method of thermogravimetric analysis was used to determine the phase hydra-
tion degree in the course of cooling from 980 to 200C at = 3 10^–2 atm. Hydration enthalpies H_hydr
(52 to 67 kJ/mol) were calculated.

Keywords: La₆WO₁₂, double fluorite, proton conductivity, oxygen vacancies, impedance, thermogravimetric
analysis, hydration enthalpy

10.1134/S1023193515050092

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