Heat capacity, p-T phase diagram, and structure of Rb2KTiOF5

Elpasolite Rb 2 KTiOF 5 (space group, Fm m, Z = 4) was synthesized using a solid-phase reaction method. The temperature dependences of the heat capacity, the unit cell parameters, the structure, the permittivity, the response to an external pressure, and the Raman spectra were studied. A nonferroele...

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Bibliographic Details
Published in:Physics of the solid state 2008-11, Vol.50 (11), p.2175-2183
Main Authors: Fokina, V. D., Flerov, I. N., Molokeev, M. S., Pogorel’tsev, E. I., Bogdanov, E. V., Krylov, A. S., Bovina, A. F., Voronov, V. N., Laptash, N. M.
Format: Article
Language:English
Subjects:
Lattice Dynamics and Phase Transitions
Physics
Physics and Astronomy
Solid State Physics
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Summary:Elpasolite Rb 2 KTiOF 5 (space group, Fm m, Z = 4) was synthesized using a solid-phase reaction method. The temperature dependences of the heat capacity, the unit cell parameters, the structure, the permittivity, the response to an external pressure, and the Raman spectra were studied. A nonferroelectric phase transition was revealed at T 0 = 215 K; the transition is accompanied by a tetragonal distortion of the unit cell (space group I 4/ m, Z = 10) and a change in the entropy (Δ S 0 = R ln8), which is anomalously large for perovskite-like oxyfluorides with atomic cations. The specific features of the mechanism of structure distortion are discussed in combination with the previous experimental data obtained for cryolite (NH 4 ) 3 TiOF 5 and elpasolite Rb 2 KGaF 6 .
ISSN:1063-7834
1090-6460
DOI:10.1134/S1063783408110280