Crystallization Kinetics and Phase Development of PbO-BaO-SrO-Nb^sub 2^O^sub 5^-B^sub 2^O^sub 3^-SiO^sub 2^-Based Glass-Ceramics

The nucleation and crystallization kinetics of PbO-BaO-SrO-Nb^sub 2^O^sub 5^-B^sub 2^O^sub 3^-SiO^sub 2^-based glass-ceramics have been investigated. Strontium barium niobate (Sr^sub 0.33^Ba^sub 0.67^Nb^sub 2^O^sub 6^) with a tetragonal tungsten-bronze structure formed as the major crystalline phase, which nucleates and grows on the surface region of samples. The results of the present study showed an apparent activation energy of 193 kJ/mol for nucleation, which was controlled by the viscous flow of the glass. Quantitative X-ray analysis and differential thermal analysis showed that the rate-limiting mechanism of crystallization appeared to be a three-dimensional interfacial growth, which has an apparent activation energy of 386-430 kJ/mol, a value that is close to the dissociation of Si-O bonds in the glass system. [PUBLICATION ABSTRACT]