La_2O_3-Y_2O_3-ZrO_2纳米陶瓷粉末的制备及高温相稳定性

Preparation and High Temperature Phase Stability of La_2O_3-Y_2O_3-ZrO_2 Composite Ceramic Nanopowder

用化学共沉淀法制备4.5%Y_2O_3-ZrO_2(YSZ)和0.6%La_2O_3-YSZ、0.8%La_2O_3-YSZ、1.2%La_2O_3-YSZ(0.6La、0.8La、1.2La)(摩尔分数)纳米复合陶瓷粉末,研究了四组粉末的高温相稳定性。结果表明:采用正向滴淀方法制备的0.6La粉末(粒径～50 nm)团聚严重,而用反向滴淀方法制备的0.6La粉末(粒径～20 nm),粉末团聚少;各组前躯体粉末在600℃煅烧2 h后都呈单一四方相结构;在1200℃烧结100 h后0.6La、0.8La坯体呈单一四方相结构,无相变,YSZ和1.2La坯体都有立方相且1.2La坯体有锆酸镧相生成;在1300℃烧结100 h后0.6La,0.8La,1.2La坯体呈四方相和立方相结构,其中1.2La坯体有锆酸镧相生成,在相同条件下烧结的YSZ坯体有少量(～1.5%)单斜相产生;在1400℃烧结100 h后各组份中四方相已不能保持稳定,转化为单斜相和立方相,0.6La、0.8La、1.2La、YSZ坯体单斜相含量分别为30.5%,32%,35%,46.0%。在YSZ中添加少量La_2O_3在1300℃烧结能有效改善其高温相的稳定性。

4.5%Y2O3-ZrO2, 0.6%La2O3-YSZ, 0.8%La2O3-YSZ, 1.2%La2O3-YSZ （YSZ, 0.6La, 0.8La, 1.2La） （molar fraction） composite ceramic nanopowders were prepared by co-precipitation method using ZrOCl2-8H2O, Y（NO3）3-6H2O, La2O3 as raw materials. The synthesized powders were characterized and the phase stability was investigated. The results show that the size of 0.6La particles prepared by reverse titration method is -20 nm, and the size of particles prepared by the straight titration method is -50 nm. The agglomeration of the powder prepared by reverse titration method is also smaller than that of the powder prepared by straight titration method. After calcined at 600 ℃ for 2 h, all of the synthesized powders showed the pure tetragonal structure; after sintered at 1200 ℃ for 100 h, 0.6La, 0.8La showed the pure tetragonal structure, the cubic phase composed of both of YSZ and 1.2La and pyrochlore structure compose of 1.2La; after sintered at 1300 ℃ for 100 h, 0.6La, 0.8La, 1.2La showed the tetragonal structure, the cubic phase compose of all synthesized powders and pyrochlore structure compose of 1.2La and small fraction of monoclinic phase （-1.5%） was formed of YSZ; after sintered at 1400 ℃ for 100h, the tetragonal phase cannot keep stable, monoclinic phase compose of all the synthesized powders, the monoclinic phase content of 0.6La, 0.8La, 1.2La, YSZ is 30.5%, 32%, 35%, 46.0% respectively. The phase stability of YSZ can be modified by addition small fraction of La203 at 1300 ℃.