Gd^(3+)+Ce^(4+)共掺烧绿石型La_2B_2O_7的溶胶-凝胶法制备及其热物理性能

Preparation and Thermo-physical Properties of Gd^(3+)+Ce^(4+)Co-doped Pyrochlore-type La_2B_2O_7 Ceramics Derived from Citric Acid Sol-Gel Technique

采用柠檬酸溶胶-凝胶法制备了稀土Gd3++Ce4+共掺的La2Zr2O7新型热障涂层用陶瓷粉体La2-xGdxZr2-xCexO7(x=0.0,0.1,0.2;LGZCO)。通过X-ray衍射、扫描电子显微镜、透射电子显微镜、TG-DSC、高温热膨胀仪和激光热导仪对样品的相组成、微观形貌、热行为、热膨胀系数和热导率进行表征。结果表明:稀土Gd3++Ce4+共掺的LGZCO保持了烧绿石相结构;添加稀土Gd3++Ce4+离子不仅可以降低材料的导热系数,还有利于其热膨胀系数的提高;随着稀土Gd3++Ce4+掺杂量的增加,晶体中点缺陷浓度不断升高,声子平均自由程不断减小,使得稀土Gd3++Ce4+共掺LGZCO的热导率在x=0.2时达到最低值(κ=0.99 W/(m·K),T=1273K),该值明显低于同温度下8YSZ的热导率。Gd3++Ce4+共掺的La2Zr2O7体系是下一代新型热障涂层用陶瓷热门的候选材料之一。

The synthesis of Gd3＋ ＋Ce4＋ codoped La2Zr2O7（La2-xGdxZr2-xCexO7,x=0.0,0.1,0.2;LGZCO） ceramics derived from citric acid sol-gel method using La（NO3）3 · 6H2O, Gd（NO3）3· 6H2O, Ce（NO3）4 · 6H2O and Zr（NO3）4 ·5H2O as precursor have been investigated. The precursor, dried, and further sintered LGZCO samples were characterized by X-ray diffraction, scanning electron microscopy （SEM）, transmission electron microscope （TEM） and differential scanning calorimetry-thermogravimetry （DSC-TG）. The thermal expansion coefficients （CTE） and thermal diffusivity of these oxide materials were also evaluated by the high-temperature dilatometer and laser flash method. Those results demonstrate that all the La2-xGdxZr2-xCexO7 compositions are comprised of the pure pyrochlore La2 Zr2O7 phase. Gd3＋ ＋Ce4＋ co-doped lanthanum zirconate ceramics demonstrates low thermal conductivi- ty reduction contributed by the substaintiaI additional point-defect scattering with the decreasing phonon mean free path, jontly facilitate higher CTE. Thermal conductivity of the co-doped La2-xGdxZr2-xCexO7 composition was found to be lower than that of the 8mol% yttria-stabilized zirconia （SYSZ） and showed a minimum thermal conductivity value at the composition Lal. 8 Cod0. 2 Zr1. 8 Ce0. 2O7（k= 0. 99 W/（m · K）, T= 1273 K）. Such excellent thermo-physical properties make the La2-xGdxZr2-xCexO7 ceramics a promising candidate for the next generation advanced thermal barrier coatings.