La_2O_3在MgO-Al_2O_3-SiO_2-TiO_2微晶玻璃中的作用

Role of La_2O_3 in MgO-Al_2O_3-SiO_2-TiO_2 Glass-ceramics

在ＭｇＯ－Ａｌ２Ｏ３－ＳｉＯ２－ＴｉＯ２玻璃中添加不同数量的氧化镧，采用差热分析、Ｘ射线衍射及电子显微镜等技术研究了氧化镧对玻璃析晶过程与力学性能的影响．氧化镧的加入使玻璃中析出α－堇青石相的温度降低；同时避免了高膨胀方石英相的析出．随着氧化镧加入量的增加，玻璃整体析晶能力下降，微晶玻璃中晶相含量减少，晶粒尺寸增大，微晶玻璃的弹性模量与硬度减小，断裂韧性增加，体现出大尺寸长柱状金红石晶粒的增韧作用．

The crystallization process and mechanical properties of MgO-Al2O3-SiO2-TiO2 glass-ceramics containing La2O3 were studied by means of DTA, XRD, and SEM. With the present of La2O3, alpha-cordierite phase appears at lower temperature and no cristobalite phase exits. The tendency of bulk crystallization of glass-ceramics is declined by the addition of La2O3, which leads to small crystallinity and large crystal grains. As a result, the elastic modulus and hardness of the glass-ceramics become lower. The fracture roughness of glass-ceramics, however, is raised by the toughening effect of rutile crystalline grains with big length-diameter ratio.