Health & Environmental Research Online (HERO)


Print Feedback Export to File
8165785 
Journal Article 
Pretransitional phenomena in region of structural phase transition in sodium perchlorate 
Aliev, AR; Akhmedov, IR; Kakagasanov, MG; Aliev, ZA; Kramynin, SP 
2020 
63 
1 
64-70 
Russian 
Structural and dynamic properties and molecular relaxation processes in crystalline so-dium 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 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 tem-peratures. 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 de-creases sharply, decreasing with a further increase in temperature. The existence of a pretransi-tional 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. © Ivanovo State University of Chemistry and Technology. 
Diffuse phase transition; Ionic crystals; Molecular spectroscopy; Perchlorates; Pretransition; Raman scattering; Vibrational relaxation