EFFECT OF REPLACEMENT OF CaO BY La2O3 ON THE STRUCTURE, THERMAL AND DIELECTRIC PROPERTIES OF ALKALI-FREE ALUMINOBOROSILICATE GLASSES

Alkali-free aluminoborosilicate glasses were prepared by the conventional melting method. The effect of the replacement of CaO by La2O3 on the structure, thermal, and dielectric properties of the glasses was investigated by FTIR, DSC, with thermal expansion instruments, and an impedance analyser. With increasing ratios of La2O3 to CaO, the densities of the glasses increased linearly from 2.458 to 2.627 g center dot cm-3. Meanwhile, the polymerisation degree of the glass network increased first and then decreased. The glass transition temperature, crystallisation onset temperature and expansion softening temperature showed a gradually increasing trend, while the thermal stability firstly deteriorated, then gradually improved. Additionally, the coefficient of thermal expansion (CTE), dielectric constant and dielectric loss initially decreased, followed by an increase. The sample with the La2O3/CaO ratio of 1.00 showed excellent properties: had a low CTE (2.71 x 10-6 degrees C-1), had a dielectric constant (5.23), and a dielectric loss (1.12 x 10-3), which means it is a promising material for integrated circuit packaging applications.