SYNTHESIS OF NANOSTRUCTURED TRANSPARENT BaTiO_3 CERAMICS WITH NOVEL ELECTRONIC AND OPTICAL PROPERTIES

本研究的目的是建立一个程序纳米结构的透明本论文采用高浓度溶胶-凝胶法制备了具有新颖电学和光学性能的钛酸钡（或半透明）陶瓷，在电瓷领域取得了重大的创新，主要研究结果如下：1）BaTiO_3透明整体凝胶的合成：以高浓度的Ba、Ti醇盐溶液（1.0mol/L）为原料，在0℃下用水蒸气水解，然后在30-500℃下陈化数天，成功地合成了透明的BaTiO_3整体凝胶。2）澄清了BaTiO_3纳米晶阿利特的生成机理：发现纳米晶BaTiO_3颗粒的形成主要是由于纳米晶BaTiO_3颗粒的形成，而纳米晶BaTiO_3颗粒的形成主要是由于纳米晶BaTiO_3颗粒的形成和纳米晶BaTiO_3颗粒的形成所引起的 关于我们 3）透明凝胶的孔结构和光学性质的分析：用N_2吸附-脱附测孔仪对透明BaTiO_3凝胶的孔结构进行了表征，其孔分布在3 - 10 nm之间。BaTiO_3晶体颗粒的光吸收边比BaTiO_3体相晶体的光吸收边大，这可能是由于尺寸效应造成的。4）半透明BaTiO_3陶瓷的制备：在1100℃、氧气气氛下烧结具有特定孔结构的透明凝胶，成功地制备出半透明BaTiO_3陶瓷。该凝胶显示出不寻常的致密化行为，其特征在于在低于500℃的低温下开始显著的致密化。5）半透明BaTiO_3陶瓷的介电和光学性能的表征：测量了亚微米晶粒尺寸半透明BaTiO_3陶瓷的介电性能。半透明陶瓷已被发现表现出铁电性能，这是由一个明显的介电峰在居里温度和一个明确的磁滞回线在室温下证明。在大晶粒半透明BaTiO_3陶瓷中观察到了明显的光散射电光效应，但遗憾的是，由于目前半透明BaTiO_3陶瓷的晶粒尺寸较大，没有观察到由于尺寸效应而产生的新颖光学特性。少

The objective of this study is to establish a procedure nanostructured transparent (or translucent) barium titanate ceramics with novel electronic and optical properties by high concentration sol-gel processing, which was individually developed by us, to introduce an important innovation in the field of electroceramics.The obtained results are summarized as follows :1) Synthesis of transparent BaTiO_3 monolithic gels : We succeeded in synthesizing transparent BaTiO_3 monolithic gels from highly concentrated Ba, Ti alkoxides solution (1.0 mol/L) by hydrolyzing with water vapor at 0℃, followed by aging for several days at 30-500℃. The gel's properties, including the degree of crystallization and pore structure, were characterized quantitatively on the basis of the influenced of the amount of hydrolysis water and the hydrolysis temperature upon the properties.2) Clarification of the creation mechanism of BaTiO_3 nanocryst allites : It has been found that nanocryst alline BaTiO_3 particles … More are formed directly from the precursor solution when a sufficient amount of hydrolysis water is used.3) Analysis of the pore structure and optical properties of transparent gels : Using an N_2 absorption-desorption porosimeter the pore structure of transparent BaTiO_3 gels has been characterized to have a narrow distribution of pores in the range of 3 to 10nm. The optical absorption edge of the cryst alline BaTiO_3 particles was found to be larger than that of bulk Batio_3 crystal due to probably the size effect.4) Preparation of translucent BaTiO_3 ceramics : We succeeded in producing translucent BaTiO_3 ceramics by sintering transparent gels with a specific pore structure at 1100℃ in an O_2 at mosphere, which gels showed an unusual densification behavior that is characterized by a significant densification starting at a low temperature below 500℃.5) Characterization of dielectric and optical properties of translucent BaTiO_3 ceramics : The dielectric properties of translucent BaTiO_3 ceramics with sub-micrometer grain sizes have been measured. The translucent ceramics have been found to exhibit ferroelectric properties, which was demonstrated by a distinct dielectric peak at the Curie temperature and a well-defined hysteresis loop at room temperature. A distinct electro-optic effect of light scattering was observed for a large grain-sized translucent BaTiO_3 ceramic, though, unfortunately, novel optical properties due to the size effect was not observed for the present translucent BaTiO_3 ceramics because of their large grain sizes. Less