纳米晶Ba_（1－x）Pb_xTiO_3的合成与表征

SYNTHESIS AND CHARACTERIZATION OF Ba_(1-x)Pb_x TiO_3 NANOCRYSTALS

以醋酸铅、硬脂酸钡和钛酸丁酯为原料，用硬脂酸凝胶法（ＳＡＧ）合成了粒度均匀、粒径１０－２０ｎｍ的Ｂａ（１－ｘ）ＰｂｘＴｉＯ３纳米晶粉末．利用红外光谱（ＩＲ）、热重（ＴＧ）和差热分析（ＤＴＡ）研究了纳米晶粉末的合成过程．用ＴＥＭ、ＸＲＤ观察和研究纳米晶的形貌及晶体结构，并用发射光谱测定样品的纯度．

Ba1-xPbxTiO3 nanocrystals were synthesized by stearic acid-gel method (SAG), using stearic acid, lead acetate, barium stearate and terabutyl titanate as raw materials. The synthesis temperatures were lower than the formation temperature of perovskites oxide by conventional solid phase reaction method. The transformations of precuror to gel and to crystalline phase were characterized by infrared spectroscopy, differential thermal analysis and thermogravimatric analysis. The nanocrystalline Ba1-xbbxTiO3 samples were characterized by transmission electron microscopy and X-ray diffraction. The results show that the Ba1-xPbxTiO3 nanocrystals prepared by SAG method are spherical, non-aggregated and with grain size small as 10-20nm. Under the same heat treatment condition, the grain size increases with increasing X; while in order to obtain Ba1-xPbxTiO3 nanocrystals with the same grain size, the heat treatment temperature decreases with increasing X. It is also found that, the crystalline structures of nanocrystalline Ba1-xPbxTiO3 are greatly influenced by grain size: with decreasing grain size, the structure changes from tetragonal phase to cubic phase, which indicates that when the grain size decreases to a critical size the nanocrystalline Ba1-xPbxTiO3 turns from ferroelectric to paraelectric materials. The critical size reduces with increasing X, so that the boundary of tetragonal to cubic phase transition changes with decreasing grain size. The boundary of T-C phase transition in Ba1-xPbxTiO3 nanocrystalline materials with grain size about 20nm is nearly X=0.5; when grain size increases to 100nm, the boundary shifts to X= 0.2.The powders were further proved to be of high purity by optical emission spectroscope.