Structure and Dielectric Properties of Bi-Zn-Ti-Nb-O Ceramics

Abstract

The compositions, structure and dielectric properties of Bi _1.5+x/2 Zn _{0.5 + x/6} Ti_1.5-1.5xNb _0.5+5x/6 O ₇ (0.1 ≤ x ≤ 0.75, BZNT) ceramic in the Bi ₂ O ₃ -ZnO-Nb ₂ O ₅ - TiO ₂ quaternary system were investigated. The structure of the samples exhibits a pure pyrochlore phase with x ≤ 0.3; a small amount of impurity with x = 0.5; a coexistence of cubic pyrochlore phase and monoclinic zirconolite phase with x = 0.75. Dielectric constant at 1 MHz decrease from 191 to 112 with the increase of x. Dielectric losses of all samples remain in the level of (1∼4) × 10−4. A typical dielectric relaxation behavior was also observed in all compositions, and the temperature of the permittivity peak increased linearly with the increase of x. Q value is within the range of 50 to 70 at resonate frequency of 2∼3 GHz.

Keywords:

• Bismuth-based ceramics
• pyrochlore
• dielectric properties
• microwave characteristics

Acknowledgments

This work is supported by the Ministry of Science and Technology of China through 973-project (No. 2002CB613302), the key project of Chinese Ministry of Education (No. 108055), Shanghai Pujiang Program and National Natural Science Foundation of China (No. 10874130).