This article is cited in 4 papers

Phase transitions

Effect of cation substitution in Cs$_{1-2x}$Ba$_{x}$H$_{2}$PO$_{4}$ on structural properties and proton conductivity

V. G. Ponomareva^ab, I. N. Bagryantseva^ab, E. S. Shutova<sup>a

a</sup> Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk
^b Novosibirsk State University

Abstract: We synthesized compounds with partial substitution of Cs$^+$ cations in CsH$_{2}$PO$_{4}$ by Ba$^{2+}$ cations. The structural, electron transport and thermodynamic properties of Cs$_{1-2x}$Ba$_{x}$H$_{2}$PO$_{4}$ ($x$ = 0–0.15) were studied for the first time with the help of a set of physicochemical methods: infrared and impedance spectroscopy, X-ray diffraction and synchronous thermal analysis. The proton conductivity of Cs$_{1-2x}$Ba$_{x}$H$_{2}$PO$_{4}$ at 50–230$^\circ$C was investigated in detail by impedance measurements. The formation of solid substitution solutions isostructural with CsH$_{2}$PO$_{4}$ ($P$2$_{1}/m$) is observed in the range of substitution degrees of $x$ = 0–0.1, with a slight decrease in the unit cell parameters and some salt amorphization. The conductivity of disordered Cs$_{1-2x}$Ba$_{x}$H$_{2}$PO$_{4}$ in the low-temperature region increases by two orders of magnitude at $x$ = 0.02 and increases with an increasing fraction of barium cations by three or four orders of magnitude at $x$ = 0.05–0.1; the superionic phase transition practically disappears. At $x$ = 0.15, heterophase systems based on salts are formed, showing high conductivity and a further decrease in the activation energy of conductivity to 0.63 eV. The conductivity of the high-temperature phase of Cs$_{1-2x}$Ba$_{x}$H$_{2}$PO$_{4}$ does not change with increasing fraction of the substituent.

Received: 29.11.2016

DOI: 10.21883/FTT.2017.07.44601.429

 English version: Physics of the Solid State, 2017, 59:7, 1387–1394

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