Preparation, structure and dielectric properties of bismuth-based ceramic dielectrics

Preparation, structure and dielectric properties of bismuth-based ceramic dielectrics were investigated. Samples of 0.75Bi(2)O(3) : ZnO : 0.75A(2)O(5) (A=Nb, Ta) were prepared by conventional ceramic technology, sintered below 1000 degrees C. Eased on X-ray diffraction analysis, the structure of 0.75Bi(2)O(3) : ZnO : 0.75Nb(2)O(5) (BZN) composition is characterized as cubic pyrochlore, while the 0.75Bi(2)O(3) : ZnO : 0.75Ta(2)O(5) (BZT) composition is a multiphase ceramic with two cubic fluorites and an orthorhombic pyrochlore structures. The bismuth-based ceramic dielectrics have excellent electrical resistivity greater than 10(14) ohm-cm. The BZN dielectric has dielectric constant around 130, the room temperature dissipation factor is less than 4 x 10(-4) from 10KHz to 1MHz, and the temperature coefficient of the dielectric constant is about -470 ppm/degrees C. While in BZT composition, the dielectric constant decreases to 80, the dissipation factor deteriorates to 5 x 10(-3), and the temperature coefficient increases to +60ppm/degrees C.