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

本研究的目的是建立一种具有新的电学和光学性能的纳米结构透明(或半透明)钛酸钡陶瓷，这是我们自主研发的一项新工艺，旨在引入电陶瓷领域的一项重要创新。1)透明BaTiO3整体凝胶的合成：我们成功地以高浓度BaTiO4醇盐溶液(1.0℃/L)为原料，在0℃水蒸气中水解，然后在30-500℃下老化数天，成功地合成了透明BaTiO3整体凝胶。在考察了水解水量和水解温度对凝胶性能影响的基础上，对凝胶的结晶度和孔结构等性能进行了定量表征。2)阐明了BaTiO_3纳米晶的形成机理：发现纳米晶BaTiO_3粒子…3)透明凝胶的孔结构和光学性质的分析：用N_2吸附-脱附孔隙仪表征了透明BaTiO_3凝胶的孔结构，其孔分布在3~10 nm范围内。4)半透明BaTiO_3陶瓷的制备：我们成功地制备了具有特定孔结构的透明凝胶，这种凝胶在1100℃的大气压氧气中烧结，凝胶表现出异常的致密化行为，其特征是在低于500℃的低温下开始显著致密化。5)半透明BaTiO_3陶瓷的介电和光学性能表征：测量了亚微米级BaTiO_3陶瓷的介电性能。半透明陶瓷具有铁电特性，居里温度下有明显的介电峰值，室温下有明显的磁滞回线。在大颗粒半透明BaTiO_3陶瓷中观察到了明显的光散射电光效应，但遗憾的是，目前的半透明BaTiO_3陶瓷由于其大颗粒尺寸而没有观察到由于尺寸效应而产生的新的光学性质。较少

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