Effects of CaO on crystallization properties in BaO–SrO–TiO2–SiO2 glass–ceramics

The role of calcium oxide (CaO) was investigated in the crystallization of BaO–SrO–TiO2–SiO2 glass. The CaO dopant altered the oriented growth facets of crystal unit cells in the glass–ceramics. The crystallites are acicular in micron scale in the samples having as small as 1% CaO dopant, but are long granular in the nanometer scale in the sample without CaO. The glass–ceramics which have nano crystallites are observed with a less crystallization density qualitatively, a higher transmissivity in the wavelength range of 200–2600 nm, and 30% lower piezoelectric coefficient, d33, at 9.5 ± 0.3 pC/N than those glass–ceramics having CaO in the study.