中文摘要：

La_2O_3-TiO2非晶氧化物是一种具有优异光学性能的材料,有着广泛的应用前景,但其非晶形成能力较差,通过无容器凝固制备的材料尺寸通常在10 mm以下。为了获得大尺寸La_2O_3-TiO_2非晶氧化物材料,本研究在La_2O_3-TiO_2氧化物体系中加入少量SiO_2。先通过气动悬浮技术制备非晶粉末,然后用真空热压烧结的方式制备出了高致密度的大块La_2O_3-TiO_2-SiO_2材料,并用XRD、SEM等技术手段进行表征。结果表明：SiO_2可以提高La_2O_3-TiO_2体系的非晶形成能力,通过气动悬浮技术获得的原料粉末呈完全非晶态,通过热压烧结方式获得的块体材料高度致密,仅存在少量的气孔。烧结样品有微弱的晶化,晶化是其无法完全致密的一个重要原因。通过研究烧结曲线,分析了La_2O_3-TiO_2-SiO_2非晶粉末的烧结机制。烧结的La_2O_3-TiO_2-SiO_2材料在可见光区域的折射率大于2.2,具有优异的光学性能。

英文摘要：

La203-TiO2 amorphous oxide has prospective applications because of its remarkable optical properties. However, due to its poor glass-forming abilities, it is difficult to prepare this material in a traditional way. The contain- erless solidification method can overcome this shortcoming, but the formed material size is generally restricted to be less than 10 mm. In order to obtain large-sized La203-TiO2 amorphous oxide, a small amount of SiO2 was added to the La203-TiO2 oxide system to form the amorphous oxide powders by aerodynamic levitation furnace. Subsequently, the high-density La203-TiO2-SiO2 materials were fabricated by vacuum hot press sintering. Compositions and microstruc- ture properties were systematically studied by XRD and SEM. The results showed that SiO2 could improve the glass-forming ability of La203-TiO2. The raw powders made by aerodynamic levitation fiLrnace were completely non-crystal, while the sintered samples had weak crystallization, which affected fully densification of sintered samples. There was a small amount of porosity in the high-density product made by vacuum hot press sintering. In addition,sintering densification mechanism of the La203-TiO2-SiO2 amorphous powders was analyzed. Finally, the optical property of hot pressed La2Oa-TiO2-SiO2 material was investigated. It is found that La203-TiO2-SiO2 material still kepts high refractive index of above 2.2 in the visible light region. Small amount addition of SiO2 species improves the glass-forming abilities, yet decreases the refractive index slightly.