白云石
焓
量热法
热容
差示扫描量热法
吉布斯自由能
煅烧
标准摩尔熵
热力学
化学
材料科学
分析化学(期刊)
矿物学
磷灰石
生物化学
物理
色谱法
催化作用
作者
Guishang Pei,Mengjiao Jiao,Zhuoyang Li,Yongda Li,Ningyu Zhang,Yuntao Xin,Xuewei Lv
摘要
Abstract Ca 3 (VO 4 ) 2 is a promising candidate for applications in ferroelectric, laser host, and optical materials owing to its unique whitlockite structure and excellent physicochemical properties. In this study, the Ca 3 (VO 4 ) 2 powder was fabricated via a conventional solid‐phase route in air, using V 2 O 5 and CaO as precursors. The trigonal Ca 3 (VO 4 ) 2 belongs to the space group R 3 c , having unit cell parameters of a = 10.8074 Å, b = 10.8074 Å, and c = 37.98871 Å, respectively. Ca 3 (VO 4 ) 2 melts congruently at 1680 K, as determined from differential scanning calorimetry measurements of the thermal profile of the second heating test. Enthalpy changes in Ca 3 (VO 4 ) 2 were experimentally determined for the first time across temperatures between 573 and 1623 K by drop calorimetry. The temperature‐dependent molar heat capacity of Ca 3 (VO 4 ) 2 was calculated from the enthalpy changes at elevated temperatures. Thermodynamic properties (entropy, enthalpy, and Gibbs free energy changes) were also calculated. The thermodynamic properties measured in this study were further applied to evaluate the appropriate precursors for fabricating Ca 3 (VO 4 ) 2 via solid‐state calcination. The results strongly recommend the use of V 2 O 5 and Ca(OH) 2 precursors for preparing the Ca 3 (VO 4 ) 2 samples because of their thermodynamic advantages.
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