Dielectric Studies of NaNH4(SO4)1-x(SeO4)x·2H2O on the Phase Transition

Autor:	Yasuharu Makita, Akio Miyazaki, Toshio Osaka, Masaru Komukae, Hiroyo Ono, Katsumi Irokawa
Rok vydání:	1993
Předmět:	Permittivity Phase transition Materials science Phase (matter) Analytical chemistry General Physics and Astronomy Dielectric Atmospheric temperature range Hydrate Ferroelectricity Phase diagram
Zdroj:	Journal of the Physical Society of Japan. 62:4194-4197
ISSN:	1347-4073 0031-9015
DOI:	10.1143/jpsj.62.4194
Popis:	Dielectric constants of a NaNH 4 (SO 4 ) 1- x (SeO 4 ) x ·2H 2 O system along the c axis under stress-free and clamped conditions were measured in a temperature range from -210°C to 30°C. Examinations of the pyroelectric current were also carried out. The dielectric constants under stress-free and clamped conditions followed the Curie-Weiss law above the phase transition temperature. It was therefore suggested that the phase transition of the NaNH 4 (SO 4 ) 1- x (SeO 4 ) x ·2H 2 O system is caused predominantly by dielectric instability. A phase diagram of the NaNH 4 (SO 4 ) 1- x (SeO 4 ) x ·2H 2 O system was established from the results of dielectric measurements. It was found that the phase transition temperature of the NaNH 4 (SO 4 ) 1- x (SeO 4 ) x ·2H 2 O system exhibits a minimum value of -200°C at x =0.3. The space group in the ferroelectric phase of NaNH 4 SO 4 ·2H 2 O was identified to be P 2 1 from the phase diagram.
Databáze:	OpenAIRE
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