Temperature-induced changes in the single-crystal structure of K9H7(SO4)8 · H2O

• Published in: Crystallography reports 2013-05, Vol.58 (3), p.393-400
• Main Authors: Makarova, I. P., Grebenev, V. V., Chernaya, T. S., Verin, I. A., Dolbinina, V. V., Chernyshov, D. Yu, Koval’chuk, M. V.
• Format: Article
• Language: English
• Subjects: Crystallography and Scattering Methods; Physics; Physics and Astronomy; Structure of Inorganic Compounds
• ISSN: 1063-7745; 1562-689X
• DOI: 10.1134/S1063774513030139

Interest in superprotonic crystals of M m H n ( X O 4 ) ( m + n )/2 is associated with the solution to the fundamental problem of modern condensed matter physics: investigations of structural phase transitions and the stabilization of phases with high proton conductivity with the aim of designing new functional materials. The available data suggest that changes in the physical properties in these crystals can occur through different structural mechanisms. To reveal the structural conditionality for anomalies in the physical properties, the crystals of K 9 H 7 (SO 4 ) 8 · H 2 O were studied by X-ray diffraction in the temperature range of 25–463 K, and the crystal structure of the high-temperature phase was determined at 418 K (sp. gr. Pcan ). The results of the study indicate that the occurrence of high conductivity in K 9 H 7 (SO 4 ) 8 · H 2 O crystals at high temperatures is associated with the diffusion of water of crystallization, the hydrogen-bond network rearrangement, and the motion of K ions. The hydrogen-bond rearrangement and the hindered back diffusion of water to the crystal stabilize the high-temperature phase and ensure its supercooling to low temperatures.