Thermodynamic modeling of ZrO_(2)−CaO−TiO_(2)system

ZrO_(2)−CaO−TiO_(2)体系的热力学模拟

The phase diagram of ZrO_(2)−CaO−TiO_(2)system was essential for the development of photocatalytic materials and refractory materials.In this work,the ZrO_(2)−CaO−TiO_(2)system was accessed by using the CALPHAD method.The substitutional solution models were used to describe liquid and solid solution phases,the sub-lattice models were used to describe ternary compounds,and then the thermodynamic parameters were obtained by the least square method combined with literature experiment results.The acquired thermodynamic parameters were used to calculate the isothermal sections of the ZrO_(2)−CaO−TiO_(2)system at 1473 and 1673 K.There existed a good agreement between experimental and predicted phase relationships,the experimental points which were inconsistent with calculated results may be attributed to experimental errors and the sluggish kinetics of cations for ZrO_(2)-based materials.In order to further verify the validity of the database,the thermodynamic parameters were also used to simulate the thermodynamic properties(specific heat capacity,enthalpy,and entropy)of CaZrTi_(2)O_(7) within 5%errors.Good consistency demonstrated that the present thermodynamic database was self-consistent and credible.

ZrO_(2)−CaO−TiO_(2)体系相图对光催化材料和耐火材料的发展至关重要。采用CALPHAD方法研究ZrO_(2)−CaO−TiO_(2)体系。亚正规溶体模型用于描述液相和固溶相,亚点阵模型用于描述三元化合物。然后,结合文献实验结果,利用最小二乘法得到热力学参数。应用本研究优化的热力学参数,计算1473和1673 K下ZrO_(2)−CaO−TiO_(2)的等温截面,实验和计算的相关系吻合很好,部分不匹配的实验点误差可归结于实验误差和氧化锆基材料的动力学缓慢特性。为了进一步证实该数据库的有效性,利用该数据库模拟CaZrTi_(2)O_(7)化合物的比热容、熵和焓等热力学性能,模拟得到的误差范围在5%以内。模拟结果表明,本次优化的数据库是自洽和可靠的。