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Kinetics of Nonisothermal Crystallization of Bi 2 Sr 2 CaCu 2 O x Glasses with Different Copper Valence States
Author(s) -
Komatsu Takayuki,
Sato Ryuji,
Kuken Yusuke,
Matusita Kazumasa
Publication year - 1993
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1993.tb04018.x
Subject(s) - crystallization , activation energy , differential scanning calorimetry , copper , crystal (programming language) , analytical chemistry (journal) , glass transition , materials science , crystal growth , mineralogy , kinetic energy , thermal stability , crystallography , chemistry , thermodynamics , metallurgy , polymer , physics , computer science , composite material , programming language , organic chemistry , chromatography , quantum mechanics
The kinetics of the nonisothermal crystallization process in Bi 2 Sr 2 CaCu 2 O x glasses with different copper valance states, R(Cu + ) = Cu + /(Cu + + Cu 2+ ) = 0.79–0.99, were examined by using differential scanning calorimetry. Four different kinetic equations were used for the data analyses. It was found that the values of activation energy for crystal growth, E a , decreased with increasing Cu + content. The value of E a , which was estimated from the modified Ozawa equation, for the glass with R(Cu + ) = 0.79 was 483 kJ·mol ‐1 and for the glass with R(Cu + ) = 0.99 was 353 kJ·mol ‐1 . In the former glass, the number of crystal nuclei was almost independent of the heating rate. But, in the latter glass, the number of crystal nuclei varied significantly with the heating rate. The crystallization mechanism in the glasses was closely related to the thermal stability and viscosity of glasses: the glass with R(Cu + ) = 0.99 showing a high thermal stability and a low activation energy for viscous flow had a small value of E a . The plot of In ( T p 2 /α) against 1/ T p , where T p and α are crystallization peak temperature and heating rate, respectively, gave a reasonable value of E a for the glass with R(Cu + ) = 0.79 but was unsuitable for the evaluation of E a for crystal growth of the glass with R(Cu + ) = 0.99.