Preparation, crystallization, microstructure and dielectric properties of lead bismuth titanate borosilicate glass ceramics

Various bulk and transparent glasses were prepared by rapid melt quenching technique in the glass system 55[(PbxBi1-x)TiO3]-44[2SiO(2)B(2)O(3)]-La2O3 (x = 0-0.7). The X-ray diffraction (XRD) studies of the glass samples confirmed the amorphous nature. The differential thermal analyses (DTA) were carried out from room temperature to 900 degrees C with a heating rate of 10 degrees C/min. The DTA patterns of the samples showed one or more exothermic sharp peaks shifting towards lower temperature side with increasing concentration of bismuth oxide (BiO). On the basis of DTA results, the solid solution of bismuth titanum oxide (Bi2Ti2O7)/lead bismuth titanium oxide (Pb3Bi4Ti6O21) was precipitated in borosilicate glassy matrix as a major phase. The glasses were subjected to 4 h and 8 h heat treatment schedules to convert into glass ceramics. XRD analysis of these glass ceramic samples showed that the major crystalline phase of the entire glass ceramic samples with 0 <= x <= 0.5 is found to have cubic crystal structure, while it is tetragonal for glass ceramic sample with x = 0.7. The scanning electron microscopy (SEM) micrographs indicated the uniform distribution of Bi2Ti2O7 and Pb3Bi4Ti6O21 crystallites in the glassy matrix.