Nanosized hexagonal Mn- and Ga-doped BaTiO3 with reduced structural phase transition temperature

2011 ◽  
Vol 98 (13) ◽  
pp. 132909 ◽  
Author(s):  
Hidesada Natsui ◽  
Chikako Moriyoshi ◽  
Fumiko Yoshida ◽  
Yoshihiro Kuroiwa ◽  
Tatsuya Ishii ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Structural Phase Transition ◽  
Structural Phase

scholarly journals PRETRANSITIONAL PHENOMENA IN REGION OF STRUCTURAL PHASE TRANSITION IN SODIUM PERCHLORATE

2019 ◽  
Vol 63 (1) ◽  
pp. 64-70
Author(s):  
Amil R. Aliev ◽  
Isa R. Akhmedov ◽  
Murad G. Kakagasanov ◽  
Zakir A. Aliev ◽  
Sergey P. Kramynin
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Sodium Perchlorate ◽  
First Order ◽  
Temperature Range ◽  
Temperature Dependences ◽  
Increasing Temperature

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.

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