(La1-xMgx)2Ce2O7-x的合成与热物理性能

Mg对La₂Ce₂O₇的掺杂可提高其热膨胀系数、降低其热导率, 从而改善其作为热障涂层材料的性能。采用溶胶-凝胶法制备了(La_1-xMg_x)₂Ce₂O_7-x系列组成样品。X射线测试表明: 当 0≤x≤0.4时, 所有(La_1-xMg_x)₂Ce₂O_7-x 样品均与La₂Ce₂O₇具有相同的缺陷萤石结构, 且晶胞参数随x的增大而递减; 当x?0.4时, 样品中出现MgO的峰。在组成相同的情况下, 样品(La_1-xMg_x)₂Ce₂O_7-x (0≤x≤0.4)的热膨胀系数随温度升高而增大, 而热导率随温度升高而降低。在相同温度下, 不同组成样品(La_1-xMg_x)₂Ce₂O_7-x (0≤x≤0.4)的热膨胀系数随x的增大而增大; 而样品的热导率则随Mg掺杂量的增加呈先增大后减小的趋势。在此基础上, 探讨了Mg掺杂对La₂Ce₂O₇的物相、晶胞参数、热膨胀系数以及热导率的影响机理。

Synthesis and Thermophysical Properties of (La1-xMgx)2Ce2O7-x

Doping magnesium into La₂Ce₂O₇ can increase its thermal expansion coefficient (TEC) and decrease its thermal conductivity (TC), thus improve its performance for thermal barrier coating (TBC). (La_1-xMg_x)₂Ce₂O_7-x ceramics were prepared by Sol-Gel method. Powder X-Ray diffraction results revealed that (La_1-xMg_x)₂Ce₂O_7-x showed the identical structure as La₂Ce₂O₇ (defect-fluorite type), and the crystal parameter decrease with increasing x value in the range of 0≤x≤0.4, and MgO occurred in the product when x?0.4. The TEC of (La_1-xMg_x)₂Ce₂O_7-x sample (0≤x≤0.4) with the same composition increases with the increasing temperature, whereas the TC presents the opposite trend. At the same temperature, the TEC of the (La_1-xMg_x)₂Ce₂O_7-x sample (0≤x≤0.4) with different composition increases with increasing x value whereas the TC increases firstly and then decreases with the increasing of x value, where x=0.2 nearby as turning point. In addition, possible mechanisms of the influence of Mg doping on the structure, crystal parameter, TEC and TC of La₂Ce₂O₇ are discussed.