Microwave Characteristics of TiO₂-Bi₂O₃ Dielectric Resonator

The microwave characteristics of the binary-system TiO₂-Bi₂O₃ ceramics, which is widely known to exhibit a comparatively high dielectric constant in the lower-frequency band, are investigated from a new standpoint. It is shown in this article that the composition of 0.919TiO₂-0.081Bi₂O₃ has a high dielectric constant (ε_r=80), high Q (1800 at 5 GHz) and low temperature coefficient of resonant frequency (τ_f=+21 ppm/°C). From the X-ray diffraction and X-ray microanalysis, it is indicated that the crystal structure of this material is composed of two phases, TiO₂ and Bi₂Ti₄O₁₁, which possess a high ε_r with a negative temperature coefficient and a high ε_r with a positive temperature coefficient, respectively. The measurements of linear thermal expansion and temperature coefficient of capacitance are also carried out in order to study the behavior of temperature compensation in this system.