Effect of alkaline-earth oxides on the structure of lithium silicate glasses and their glass-ceramic derivatives by ultrasonic and X-Ray diffraction techniques

ABSTRACT

Lithium silicate glasses of the composition [65% SiO[2] + 30%Li[2]O + 5% RO [mol%]]; where RO is one of the divalent oxide MgO, CaO, SrO or BaO, and their glass ceramic derivatives were examined using ultrasonic technique and x-ray diffraction for studying their structures. Also, the density of the samples was measured. Ultrasonic velocity measurements were carried out using 4 MHz longitudinal and shear wave probes at room temperature. The elastic moduli, Poisson's ratio, Debye temperature and softening temperature of the prepared samples were calculated. The results show that, the ultrasonic velocities [longitudinal and shear], the shear and Young's elastic moduli decrease as the divalent oxide is changed from MgO, CaO, SrO or BaO, respectively. Meanwhile, the density, the molar volume, Debye temperature, softening temperature and Poisson's ratio increase. The variations in the different physical parameters were correlated and discussed in relation to composition and compactness of the respective glass