Microwave Dielectric Properties of BiCu₂PO₆ Ceramics with Low Sintering Temperature

A BiCu₂PO₆ microwave dielectric ceramic was prepared using a solid-state reaction method. As the sintering temperature increased from 800°C to 880°C, the bulk density of BiCu₂PO₆ ceramic increased from 6.299 g/cm³ to 6.366 g/cm³; the optimal temperature was 860°C. The best microwave dielectric properties [permittivity (ɛ_r) = ∼16, a quality factor (Q × f) = ∼39,110 GHz and a temperature coefficient of resonant frequency (τ_f) = ∼−59 ppm/°C] were obtained in the ceramic sintered at 860°C for 2 h. Then, TiO₂ with a positive τ_f (∼+400 ppm/°C) was added to compensate the τ_f value. The composite material was found to have a near-zero τ_f (+2.7 ppm/°C) and desirable microwave properties (ɛ_r = 19.9, Q × f = 24,885 GHz) when synthesized at a sintering temperature of 880°C. This system could potentially be used for low-temperature co-fired ceramics technology applications.