Non-isothermal crystallization kinetics of calcium pyroniobate (Ca2Nb2O7) in SiO2-CaO-Nb2O5-Na2O-MgO-Al2O3 glass

The crystallinity of Ca2Nb2O7 in glass-ceramics affects the piezoelectric ability for lead-free piezoelectric materials, but the growth and nucleation mechanism of Ca2Nb2O7 in glass is unclear. In this study, the nonisothermal crystallization kinetics of Ca2Nb2O7 in SiO2-CaO-Nb2O5-Na2O-MgO-Al2O3 glass was investigated through the differential scanning calorimetry (DSC) and X-Ray Diffraction (XRD). The activation energy was calculated, and the activation energies in the onset crystallization temperature (Ex) and the crystallization peak temperature (Ep) are 488.722 +/- 2.596 kJ center dot mol- 1, 440.085 +/- 2.137 kJ center dot mol-1, respectively. The crystallization and growth mechanism of Ca2Nb2O7 were investigated through the Kazumasa Matusita's method. The crystallization mechanism of Ca2Nb2O7 is bulk nucleation and the growth mechanism of Ca2Nb2O7 tends to twodimensional. The Ca2Nb2O7 nucleation process is heterogenous nucleation which is caused by earlier crystallized akermanite and magnesium silicate. The non-isothermal crystallization kinetics study may provide useful information for preparing Ca2Nb2O7-containing glass ceramics.