Barium Titanate-Based Glass–Ceramics Crystallized from Multicomponent Oxide Glasses: Phase Composition and Microstructure

The interest in synthesizing new dielectric materials is caused by their potential application in various electronic and sensor devices as well as in a large variety of electronic components. The present work reports the synthesis of glasses in the Na₂O/Al₂O₃/BaO/ZrO₂/TiO₂/B₂O₃/SiO₂ system prepared by melt-quenching. These glasses were then crystallized to glass-ceramics by a controlled thermal treatment. X-ray diffraction experiments reveal the precipitation of Ba₂TiSi₂O₈ (fresnoite) and BaTiO₃, which probably forms a BaZr_xTi_1-xO₃ solid solution. The microstructure is studied by scanning electron microscopy and shows the presence of mulberry-shaped, crystallized structures with a densely-branching morphology. Microcomputed X-ray tomography is used to gather information on the volume fraction and average size of the crystallized volume as an effect of the applied temperature-time schedule. Longer annealing times lead to a higher volume fraction and increasing average size of the crystallization structures obtained. The dielectric properties analyzed by impedance spectroscopy are insulating and show relatively high dielectric constants ≥ 100 and moderate loss tangent values at 10 kHz.