Effect of cation substitution in Cs1–2xBaxH2PO4 on structural properties and proton conductivity

• Published in: Physics of the solid state 2017-07, Vol.59 (7), p.1387-1394
• Main Authors: Ponomareva, V. G., Bagryantseva, I. N., Shutova, E. S.
• Format: Article
• Language: English
• Subjects: Phase Transitions; Physics; Physics and Astronomy; Solid State Physics
• ISSN: 1063-7834; 1090-6460
• DOI: 10.1134/S1063783417070174

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 1–2 x 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 1–2 x Ba x H 2 PO 4 at 50–230°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 1–2 x 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 1–2 x Ba x H 2 PO 4 does not change with increasing fraction of the substituent.