Phase transitions

Specific heat, cell parameters, phase $T$–$p$ diagram, and permittivity of cryolite (NH$_4$)$_3$Nb(O$_2$)$_2$F$_4$

V. D. Fokina^a, A. F. Bovina^a, E. V. Bogdanov^a, E. I. Pogoreltsev^a, N. M. Laptash^b, M. V. Gorev^ac, I. N. Flerov<sup>ac

a</sup> L. V. Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, Krasnoyarsk
^b Institute of Chemistry, Far East Branch of the Russian Academy of Sciences, Vladivostok
^c Institute of Engineering Physics and Radioelectronics, Siberian Federal University, Krasnoyarsk

Abstract: The temperature dependences of the specific heat, unit cell parameters, susceptibility to hydrostatic pressure, and permittivity of cryolite (NH$_4$)$_3$Nb(O$_2$)$_2$F$_4$ have been studied. Phase transitions of nonferroelectric nature have been detected. Entropy parameters point to the relation of structure distortions to ordering processes.

Received: 17.03.2011

 English version: Physics of the Solid State, 2011, 53:10, 2147–2153

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