(NH4)3HfF7: Crystallooptical and calorimetric studies of a number of successive phase transitions
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URI (для ссылок/цитирований):
https://www.sciencedirect.com/science/article/abs/pii/S0022113917303445https://elib.sfu-kras.ru/handle/2311/111326
Автор:
Evgeniy, Pogoreltsev
Evgeniy, Bogdanov
Svetlana, Melnikova
Igor, Flerov
Nataly, Laptash
Коллективный автор:
Институт инженерной физики и радиоэлектроники
Кафедра теплофизики
Дата:
2017-12Журнал:
Journal of Fluorine ChemistryКвартиль журнала в Scopus:
Q2Квартиль журнала в Web of Science:
Q2Библиографическое описание:
Evgeniy, Pogoreltsev. (NH4)3HfF7: Crystallooptical and calorimetric studies of a number of successive phase transitions [Текст] / Pogoreltsev Evgeniy, Bogdanov Evgeniy, Melnikova Svetlana, Flerov Igor, Laptash Nataly // Journal of Fluorine Chemistry. — 2017. — Т. 204. — С. 45-49Аннотация:
Single crystals of (NH4)3HfF7 were grown. Polarising optical observations as well as measurement of the heat capacity and birefringence Δn(Т) were performed in the temperature range of 200–310 K. Reversible phase transitions at temperatures T0 =290 K, Т1 =280.5 K, Т2 ≈273 K, Т3 =266 K, Т4 =259 K, Т5 =231 K, Т6 =229 K were found. Observations in polarised light make it possible to suggest a sequence of changes in the symmetry groups for these transitions. The T-p phase diagram was studied and the temperature boundaries of the stability of the distorted crystalline phases were determined. A significant change of the entropy at successive phase transitions
ΣΔS =10.6 J/mol K indicates a disordering of the initial cubic phase.