期刊
JOURNAL OF FLUORINE CHEMISTRY
卷 183, 期 -, 页码 1-9出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jfluchem.2015.12.010
关键词
Fluorides; Structural disorder; Phase transitions; Entropy; Barocaloric effect
资金
- RFBR [15-02-02009a]
Structural phase transition P-3m1 <-> P-1 of the first order and nonferroelectric nature was found in (NH4)(2)SnF6 at about 110 K in the process of thermal, optical, dielectric and X-ray studies. Order-disorder transformation is accompanied by large changes of entropy (Delta S-0 = 16.4J/mol K) and volume (Delta V-0/V approximate to 1%). The structural model associated with three orientations of NH4 tetrahedra in P-3m1 phase and their complete ordering in P-1 phase was suggested with the entropy change (Delta S-0 = 18.3 J/mol K) close to the experimental value. A good agreement between baric coefficients measured in a direct way (dT(0)/dp = -157 K/GPa) and evaluated using entropy and volume changes at phase transition (-170 K/GPa) was found. Barocaloric effects in (NH4)(2)SnF6 are comparable with those of known solid state refrigerants and are characterised by a low-pressure need for realising their maximum values. (C) 2015 Elsevier B.V. All rights reserved.
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