Microstructure and Dielectric Properties of Bismuth Germanate Glass-Ceramics

Abstract

Bismuth germanate composites containing Bi₂GeO₅-Bi₄Ge₃O₁₂ phases were prepared by glass ceramic method and sintering techniques. The existences of three bismuth germanate crystals of Bi₂GeO₅, Bi₄Ge₃O₁₂ and BiBO₃ were found in XRD patterns. The amount of each phase depended mostly on the sintering temperature where the Bi₄Ge₃O₁₂ phase was found to increase with increasing sintering temperature. The mixing of round and pyramidal shape crystals was observed in the sample sintered at 650°C. This gave rise to the improvement in its dielectric properties where the ϵ_r was found to increase from ∼78 to ∼395 for the sample sintered at 500°C and 650°C, respectively. Moreover, the tanδ was found to decrease greatly with increasing sintering temperature. Thus, this Bi₂GeO₅-Bi₄Ge₃O₁₂ composite may be considered as a promising candidate of microwave dielectric materials.

Keywords:

• Bismuth germanate
• glass-ceramics
• dielectric properties

Acknowledgments

The authors would like to express their sincere gratitude to the Thailand Research Fund (TRF) and Faculty of Science, Chiang Mai University for their financial support. P.Kantha is also thankful for his financial support from the Royal Golden Jubilee Ph.D. Program and the Graduate School of Chiang Mai University.