热压烧结法制备大尺寸La2O3-TiO2-SiO2非晶材料的研究

La₂O₃-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La₂O₃-TiO₂非晶氧化物材料, 本研究在La₂O₃-TiO₂氧化物体系中加入少量SiO₂。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La₂O₃-TiO₂-SiO₂材料, 并用XRD、SEM等技术手段进行表征。结果表明: SiO₂可以提高La₂O₃-TiO₂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La₂O₃-TiO₂-SiO₂非晶粉末的烧结机制。烧结的La₂O₃-TiO₂-SiO₂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。

Large-sized La2O3-TiO2-SiO2 Amorphous Oxide Fabricated by Hot Press Sintering

La₂O₃-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 containerless 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 La₂O₃-TiO₂ amorphous oxide, a small amount of SiO₂ was added to the La₂O₃-TiO₂ oxide system to form the amorphous oxide powders by aerodynamic levitation furnace. Subsequently, the high-density La₂O₃-TiO₂-SiO₂ materials were fabricated by vacuum hot press sintering. Compositions and microstructure properties were systematically studied by XRD and SEM. The results showed that SiO₂ could improve the glass-forming ability of La₂O₃-TiO₂. The raw powders made by aerodynamic levitation furnace 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 La₂O₃-TiO₂-SiO₂ amorphous powders was analyzed. Finally, the optical property of hot pressed La₂O₃-TiO₂-SiO₂ material was investigated. It is found that La₂O₃-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.