Mg掺杂PST薄膜的溶胶-凝胶法制备及晶相形成研究

利用溶胶-凝胶法成功制备了Mg掺杂Pb_0.4Sr_0.6Mg_xTi< sub>1-xO_3-x薄膜，利用x射线衍射仪对薄膜的物相和结构进行了分析， 用扫描电子显微镜对薄膜的形貌和断面等进行了观察.研究结果表明，薄膜以立方钙钛矿为 晶相，薄膜中晶相以团聚状颗粒存在，晶相含量受热处理条件和Mg的掺杂量所控制.Mg掺杂 对Pb_0.4Sr_0.6Mg_xTi_1-xO_3-x 薄膜晶相含量的影响与钙钛矿中的氧空位缺陷相关.在一定的掺杂范围内，由掺杂引起晶相 的晶格畸变较小时，体系掺Mg平衡了晶体内本征氧空位引入的电荷不平衡，使晶相更为稳定 ，析晶能力提高，晶体形成量随掺杂浓度的提高而提高.当掺杂浓度达到一定量时， 随着Mg 掺杂浓度增加，一方面使形成晶体时杂质浓度增加造成参与形成晶相的组成含量下降，另一 方面使进入钙钛矿结构的Mg增加，氧空位大量增加使畸变程度提高，形成的晶相不稳定，析 晶能力下降，晶体含量随掺杂Mg浓度的增加而不增反降.在相同条件下制备的Pb_{0.4Sr0.6MgxTi1-xO3-x薄膜中Mg掺量约为 x=0.01时，得到的钙钛矿相含量最高，本征氧缺陷所带入的正电荷和Mg引入时带入的负电荷 间达到平衡.此外，Mg的掺入还影响到析晶与热处理过程之间的关系.在高Mg掺量范围，Mg含 量越高，形成的晶相越不稳定，热处理时间越长，使热处理过程中分解的晶相量越多，随Mg 掺量越高和热处理时间越长，薄膜中晶相含量越低. 关键词： 溶胶-凝胶法 PST薄膜 Mg掺杂 晶相形成}

Preparation and phase formation of sol-gel derived PST thin film doped with Mg

PST thin film doped with Mg was successfully prepared using sol-gel process. The phase structure of the thin film was measured by XRD and the morphology of microstructure of the thin film was observed by SEM. Results showed that the cubic perovskite phase is formed in Mg-doped Pb_0.4Sr_0.6Mg_{x< /sub>Ti1-xO3-x thin film prepared by sol gel process. The clustered crystallites are distributed and embedded in the base matrix of thin f ilm. However, the contents of the perovskite phase was controlled by both Mg dop ing and heat treatment condition due to formation of intrinsic oxygen vacancy in the perovskite phase. The charge balance between the positive from the intrinsi c oxygen vacancy and the negative from Mg substitution for Ti occurs when small amount of Mg is doped in the perovskite phase. The stable perovskite phase forms easily, and the crystallization of the perovskite phase is hence increased with increasing Mg doping up to x=0.01. The distortion of the perovskite phase struc ture would increase with farther increase of Mg doping in the crystallites above about x=0.01 due to the generation of a lot of oxygen vacancies. Henceforth uns table perovskite phase is formed and the crystallization of the film decreases w ith increasing Mg. Thus highest content of the perovskite phase is reached and t he charge balance between positive and negative occurs in the film when Mg dopin g is x=0.01. Furthermore, the formed crystalline phase may decompose with increa sing Mg content and time of heat treatment. So in the case of high Mg doping the higher the content of Mg and the longer the time of heat treatment, the lower t he content of perovskite phase is contained in the film.}