退火温度对Ba_(0.6)Sr_(0.4)TiO_3薄膜晶化及介电性能的影响

用改善的溶胶凝胶(Sol-Gel)法制备了钛酸锶钡(Ba_0.6Sr_0.4TiO_3, BST)薄膜,研究了退火温度对薄膜晶化及介电性能的影响.X射线衍射表明,由于薄膜较薄,各温度下衍射峰强度均微弱,但呈(110)择优取向,随温度的升高峰强度逐渐增加,也出现其他晶向的衍射峰.扫描电镜和原子力显微镜表明,改善的BST薄膜表面形貌光滑致密、无裂纹、无缩孔,随温度的升高薄膜晶化增强、晶粒逐渐长大、粗糙度增加.40 V外加电压下的介电性能大幅度提高,介电调谐率大于30%,介电损耗约0.02,其中,650 ℃对应介电调谐率45.1%和介电损耗0.0187.同时,就有关结构、介电性能及退火温度的关系进行了讨论.

Influence of Annealing Temperature on Crystallization and Dielectric Properties of Barium Strontium Titanate Films Prepared by Improved Sol-Gel Method

Ba_0.6Sr_0.4TiO_3 (BST) films were prepared by improved Sol-gel method, and the effect of annealing temperature on the crystallization and the dielectric properties of the BST films was studied. X-ray diffraction shows that the BST films exhibit weak diffraction peak intensities because the films were quite thin. From 600 to 750, 600 ℃ corresponds to the weakest (110) orientation peak intensity. As the annealing temperature increases, the (110) peak intensity gradually increases, and the other diffraction peaks also appear. Scanning electron microscope presents that the BST films, which are smooth and compact with no crack or shrinkage cavity, display improved surface morphologies. With the increasing annealing temperature the crystallization of the BST films enhances with increasing crystal size and roughness. These morphologies are also confirmed by atomic force microscope. Meanwhile, the BST films illustrate significantly improved dielectric properties with more than 30% dielectric tunability at 40 V and less than 0.02 dielectric loss (tand) at zero bias. The dielectric properties are strongly dependent on the annealing temperature. 650 ℃ corresponds to the optimum dielectric property with the highest dielectric tenability of 45.1% and the lowest dielectric loss of 0.0187. Also, the correlative mechanism among film structure, dielectric properties and annealing temperature is discussed.