La_2O_3掺杂对二硅酸锂微晶玻璃析晶行为和力学性能的影响

以P_2O_5 和 ZrO_2 为复合成核剂,Sb_2O_3为澄清剂,通过传统熔体冷却法制得掺稀土La_2O_3的SiO_2-Li_2O-K_2O- B_2O_3系统基础玻璃.利用DSC、XRD、SEM和力学性能测试等方法研究La_2O_3含量对玻璃析晶行为、析出晶相种类及微晶玻璃力学性能的影响.结果表明:La_2O_3含量对基础玻璃的第一析晶峰对应的温度影响较大,对第二析晶峰对应的温度影响不明显;当La_2O_3的含量小于0.40%(摩尔分数)时,La_2O_3的引入不改变微晶玻璃主晶相类型;当La_2O_3含量增加到0.80%时,La_2O_3直接参与晶相组成,析出LaPO_4晶相;同时,La_2O_3的引入提高了二硅酸锂晶相的析出温度;当La_2O_3含量为0.40%时,微晶玻璃的抗弯强度和弹性模量达到最高值,分别为328 MPa和143 GPa;当La_2O_3含量小于0.40%和大于1.20%时,微晶玻璃的断裂韧性随La_2O_3的增加变化较小;当La_2O_3含量为0.40%～1.20%时,微晶玻璃的断裂韧性随La_2O_3含量的增加而大幅度增加,最大断裂韧性达到3.34 MPa·m~(1/2).

Effects of doping La_2O_3 on crystallization and mechanical properties of lithium disilicate glass-ceramics

The SiO_2-Li_2O-K_2O-B_2O_3 glasses doping La_2O_3 were prepared by traditional melting quenching method, using P_2O_5 and ZrO_2 as complex nucleating agent and Sb_2O_3 as clarifying agent. The effects of La_2O_3 content on the crystallization behavior, the crystalline phase and the mechanical properties of the glass-ceramics were investigated by using of DSC, XRD, SEM and mechanical property tester. The results show that, the change of La_2O_3 content mainly influences the exothermic peak temperature rather than the second exothermic peak temperature. When La_2O_3 content is lower than 0.40% (mole fraction), the doping content of La_2O_3 does not change the main crystal phase type in the glass-ceramics. However, when the La_2O_3 content increases to 0.80%, the La_2O_3 directly involves in the lattice construction of LaPO_4 micro-crystals. At the same time, La_2O_3 doping increases the precipitation temperature of Li_2Si_2O_5 phase. When the La_2O_3 content is 0.40%, the glass-ceramics has the highest bending strength and elastic modulus, which are 328 Mpa and 143 Gpa, respectively. When La_2O_3 content is lower than 0.40% and higher than 1.20%, the fracture toughness of the glass-ceramics changes slightly with increasing La_2O_3 content. However, when La_2O_3 content is 0.40%-1.20%, the fracture toughness increases obviously with increasing La_2O_3 content, the biggest fracture toughness of the glass-ceramics reaches up to 3.34 Mpa·m~(1/2).