Electrical properties of bismuth germanate (Bi₂GeO₅) ferroelectric glass-ceramics prepared by two different methods

Abstract

Ferroelectric Bi₂GeO₅ glass-ceramics were fabricated using conventional and incorporation method. Glasses have been prepared from BiO_1.5-GeO₂-BO_1.5 ternary glass system by focusing on the region of 59 mol%BiO_1.5: 23 mol%GeO₂: 18 mol%BO_1.5. The resulting glass was analyzed by using differential thermal analysis (DTA) for determining the crystallization temperature (T_p). Then, the prepared glass pieces were heat treated at T_p. Effects of different fabrication methods on structure and electrical of the glass-ceramics were investigated. X-ray diffraction result of all glass-ceramics suggested that the main peak of glass-ceramics matched the orthorhombic structure of the pure Bi₂GeO₅ phase. Microstructures of the prepared glass-ceramics have been found to change from rod-like crystallites to bulk crystallites on modifying the fabrication method. The Bi₂GeO₅ glass-ceramics prepared by incorporation method presented higher dielectric constant than those of the Bi₂GeO₅ glass-ceramics prepared by conventional method. Moreover, the Bi₂GeO₅ glass-ceramic prepared by incorporation method possesses a large value of P_max (0.94 µC/cm²) comparing to that of the glass-ceramics prepared by conventional method (P_max = 0.73 µC/cm²). Thus, this study suggests that the incorporation method can effectively modify the microstructure of Bi₂GeO₅ glass-ceramics, resulting in the improvement of dielectric and ferroelectric properties.

Keywords:

• Bismuth germanate
• ferroelectric glass-ceramics
• electrical properties

Acknowledgements

The authors would like to express their sincere gratitude to Faculty of Science and Graduate School, Chiang Mai University for financial support. We would also like to thank the Thailand Research Fund (BRG5780015 and IRG5780013). S. Panyata would like to thank the Thailand Research Fund (TRF) Royal Golden Jubilee Ph.D Program for his scholarship.