摘要
利用DTA研究了于1200℃合成的α-Ca_3(PO_4)_2急冷试样,发现在216℃和1275℃附近存在两个吸热峰,每个峰对应一个相变过程,说明Ca_3(PO_4)_2除α、β相外,还存在两个新相。研究表明,216℃为Ca_3(PO_4)_2低温介稳相α_L向α相的转变温度,外推法给出此相变温度为212.5℃,表观激活能为100 kJ/mol。而1275℃附近则为Ca_3(PO_4)_2的α→α_H相变温度,外推相变温度为1254.3℃,表观激活能为3190kJ/mol。文中还给出Ca_3(PO_4)_2单元系统相图的示意图。
DTA was used to study the α-Ca_3 (PO_4)_2 sample prepared at 1200℃ and cooled rapidly in air. It is found that there are two endothermic peaks in the vicinity of 216℃ and 1275℃ respectively, and each peak corresponds to a process of phase transformation, thus there are two new phases in Ca_3 (PO_4)_2 besides α, β phases. Based on the above study results, it is suggested that the peak in the vicinity of 216℃ corresponds to the endothermic peak of low-temperature metastable phase to a phase transformation,that is α_L→α transfcrmationpeak. By means of extrapolation, the transformation temperature (T_p) is determined to be 212.5℃, and the apparent activation energy is 100kJ/mol. For the same reason, the endothermic peak in the vicinity of 1275℃ occurs according to α→α_H phase transformation in Ca_3(PO_4)_2, and the transformation temperature (T_p) is determined to be 1264.3℃, and the apparent activation energy is 3190kJ/mol. The schematic phase diagram of Ca_3 (PO_4)_2 single system is also given in the paper.
出处
《硅酸盐学报》
EI
CAS
CSCD
北大核心
1992年第2期117-122,共6页
Journal of The Chinese Ceramic Society
关键词
磷酸钙
相变
理论研究
α-Ca_3(PO_4)_2
phase transformation, α_L→α transformation
α→α_H transformation
