KINETIC EXPONENTS OF GRAIN GROWTH IN (Ba_(0.9)Sr_(0.1))(Ti_(0.999)Nb_(0.001))O _3 CERAMICS

[中文文摘]研究了半导化 (Ba0 .9Sr0 .1 ) (Ti0 .999Nb0 .0 0 1 )O3 陶瓷晶粒生长的动力学因子 ,采用固相反应法工艺制备该陶瓷样品 ,化学原材料为纯度高于 99%的BaCO3,SrCO3,TiO2 和Nb2 O5 等 ,并用到微量原料Al2 O3 和MnSiO3 以改善陶瓷的电学性能 .同样化学配方的 8种样品在130 0℃中保温时间分别为 1,3,6 ,10 ,30 ,6 0 ,10 0和 30 0min ,以获得晶粒生长不同程度的块状陶瓷 .利用扫描电子显微技术分析发现 ,随着保温时间的延长样品的平均晶粒尺寸变大 .经自动图像处理技术发现 ,晶粒生长的动力学因子不是常数 :在烧结初期大致为 1.5 ,而在烧结后期为 3.5 .这与大多数报道的实验和模拟结果一致.[英文文摘]In this work, the kinetic exponents of grain growth in (Ba 0.9 Sr 0.1 )(Ti 0.999 Nb 0.001 )O 3 ceramics were investigated. The samples of BST ceramics were produced by the conventional ceramic processing, the solid_state reaction method. Raw materials, BaCO 3, SrCO 3, TiO 2 and Nb 2O 5, are used, with chemical purity of higher than 99 % (in mass). In addition, two minor chemicals, Al 2O 3 and MnSiO 3, are incorporated to enhance the electrical properties of resulting ceramics. After weighed according to a required composition , the chemicals were ball-milled with purified water for about 20 h and calcined at 1 200 ℃for 2 h. They are then ground and milled again with polyvinyl alcohol ( PVA) solution binder , and , spray- dried for granulating. The dried powders are hydropressed into pellets and sintered at 1 300 ℃ for different holding times , to obtain bulk ceramics with different degrees of grain growth. It was observed by SEM that the average grain diameters became larger with the increasing of soaking time. It is found that the kinetic exponents , obtained by an automatic image processing technique , are not a constant , about 1. 5 at the early stage and 3.5 at the later period of grain growth. This is in good agreement with most of experimental and simulated results reported.香港RGC资助!项目 (97-0235