Crystallization characteristic and properties of some zinc containing soda lime silicate glasses

The crystallization behaviour of some soda lime silicate glasses modified by ZnO/CaO replacement to give the composition (Na2O)(2)center dot CaO1-x center dot(ZnO)x center dot 3SiO(2) (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been investigated using differential scanning calorimetry (DSC) and X-ray diffraction analysis (XRD). The thermal expansion coefficients and AC electrical properties in the frequency range 40 Hz-5 MHz of the obtained crystalline products were determined. Two forms of sodium calcium silicate (Na4CaSi3O9 & Na2Ca2Si3O9), sodium metasilicate-Na2SiO3, two types of sodium zinc silicate (Na(1.31)Z(n0.655)Si(1.345)O(4) & Na2ZnSiO4) and a-quartz phases were mostly developed in the crystallized glasses using various heat-treatment processes. The coefficient of thermal expansion of the obtained glass-ceramic materials are between 120 x 10(-7)degrees K-1 and 168 x 10(-7)degrees K-1 in the 25 degrees-600 degrees C temperature range. The increase of frequency generally resulted in the increase of the conductivity and decrease the dielectric constant together with the loss tangent of the glass-ceramic materials.