PRETRANSITIONAL PHENOMENA IN REGION OF STRUCTURAL PHASE TRANSITION IN SODIUM PERCHLORATE

Autor: Sergey P. Kramynin, A. R. Aliev, M. G. Kakagasanov, I. R. Akhmedov, Z. A. Aliev
Rok vydání: 2019
Předmět:
Zdroj: IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA. 63:64-70
ISSN: 2500-3070
0579-2991
DOI: 10.6060/ivkkt.20206301.6042
Popis: Structural and dynamic properties and molecular relaxation processes in crystalline sodium NaClO4 perchlorate in the temperature range from 300 K to 650 K were studied by Raman spectroscopy. The temperature dependences of the position of the maximum v (frequency), the width w and the intensity I of the spectral band, corresponding to the fully symmetric vibration v1(A) of the ClO4–1 perchlorate ion, in the spectral range from 933 cm–1 to 944 cm–1 were analyzed. The frequency v and intensity I decrease, and the width w increases with the increasing temperature. It is shown that these temperature dependences have certain features at a temperature of 460 K. With a further increase in temperature, the frequency v decreases more rapidly, the width w increases, and the intensity I decreases more intensively. In the temperature range from 460 K to the temperature Tstr = 581 K of the first order structural phase transition, we observe a deviation of the temperature dependence of the frequency and width from the linear dependences characteristic of lower temperatures. These deviations appear at a temperature of 460 K and increase with the increasing temperature and approaching the phase transition temperature. It has been established that in the crystalline sodium perchlorate NaClO4 a structural first-order phase transition is stretched. At the phase transition temperature (Tstr = 581 K), the width increases sharply, and the frequency decreases sharply, decreasing with a further increase in temperature. The existence of a pretransitional region in the studied crystalline sodium perchlorate NaClO4 was found. This pre-transition region occurs in the temperature range from 460 K to Tstr = 581 K.
Databáze: OpenAIRE
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