R_2O-MO-Al_2O_3-SiO_2玻璃的组成与其热膨胀系数的关系

Relationship between thermal expansion coefficient and composition of R_2O-MO-Al_2O_3-SiO_2 system glass

采用传统熔体冷却方法制得R2O-MO-Al2O3-SiO2多元系统玻璃(R为碱金属元素,M为碱土金属元素),玻璃组成(质量分数)为:SiO2,55.0%～65.0%;MgO,0～15.2%;CaO,0～15.2%;SrO,0～15.2%;BaO,0～15.2%;Na2O,0～15.6%;K2O,0～15.6%.通过比较不同组成玻璃的热膨胀系数,讨论该体系玻璃组成与其热膨胀系数之间的关系.研究结果表明:当玻璃中碱金属氧化物的质量分数大于17.8%时,玻璃的热膨胀系数迅速增大;对于具有相同含量的不同碱土金属的玻璃,其热膨胀系数随着碱土金属原子半径的增大而增大;当2种以上不同碱土金属共存时,热膨胀系数呈现明显的混合碱效应;当Li,Na和K 3种碱金属共存时,玻璃的热膨胀系数与组成的关系曲线出现2个极小点,且出现负的混合碱效应.

The R2O-MO-Al2O3-SiO2 system glass was prepared by conventional melt quenching technology（R stands for alkali-earth element, M stands for alkali-metal element） and the composition range（in mass fraction） of the glass is as follows： SiO2, 55. 0%～65. 0;MgO, 0～ 15.2%; CaO, 0～15.2%; SrO, 0～15.2%; BaO, 0～15. 2%; Na2O, 0～15. 6%, K2O, 0～15.6%. The relationship between the composition and the thermal expansion coefficient of the glass was investigated by comparing the thermal expansion coefficients of the glass with different chemical compositions. The results show that the thermal expansion coefficient of the glass increases sharply when the mass fraction of alkali-metal oxide is more than 17.8%, when introducing different kinds but the same quantity of alkali-earth metal oxide, the thermal expansion coefficient of the glass increases obviously with increasing the radius of alkali-earth metal ions; the mixed alkali effect appears when the glass contains a few kinds of alkali-earth metal oxides, when K^＋ , Na^＋ and Li^＋ exist simultaneously in the glass, the two minimum peaks and complex mixed alkali effect can be observed from the composition-thermal expansion coefficient curve.