Chiang Mai Journal of Science

The effects of heat treatment on properties of ferroelectric materials prepared by glass-ceramic route based on two glass compositions with different ratios of  glass forming oxides were studied. The compositions were Glass I: 20PbO – 20BaO – 25TiO₂  – 5Al₂O₃ – 15SiO₂ – 15B₂O₃ (mol%) and Glass II: 20PbO – 20BaO – 25TiO₂ – 5Al₂O₃ – 5SiO₂– 25B₂O₃ (mol%). Both glasses were heat treated at 600, 700 and 800 ^oC for 8 h to form glass-ceramics. XRD found PbTiO₃ as the primary phase but not BaTiO₃ Ferroelectric PbTiO₃ . had tetragonal perovskite structure. Increasing heat treatment temperature resulted in an increase of PbTiO₃  crystal size with an increase of c/a ratio (>1) which indicates the increase in tetragonality of PbTiO₃ phase. XRD also found crystallization of secondary phase(s) in each heat treated glass and analysis by SEM revealed that the phase composition and morphology were different for different glass compositions. The apparent densities of  these glass-ceramics were found to increase with increasing heat treatment temperature due to increase amount of  crystalline phases. The room temperature dielectric constants of  as-annealed glasses were about 20 and increased to values of  30 – 65 for crystallized samples.