Barium/lead-rich high permittivity glass-ceramics for capacitor applications
Dielectric properties of glass–ceramics containing barium/lead-based sodium niobates and barium titanate-based silicates were evaluated for capacitor applications. The glasses were formed by melt-rolling the respective constituents which were then crystallized by reheating them at higher temperatures. Crystallization schedules were formulated based on differential thermal analysis results. X-ray diffractometer patterns indicated that the samples were highly crystallized. Microstructure and microchemistry of samples were studied by transmission electron micropscopy. Perovskite, tungsten–bronze and fresnoite phases developed during crystallization have a strong effect on the resulted dielectric properties with permittivities ranging from 20 to 700. Resistivity measurements were done to study conduction mechanisms in samples and the resistivity values for glass–ceramics were found to be between 1011 and 1013Ω·cm at 150°C. MnO2 additions were made to improve the electrical resistivity of glass–ceramics.