High permittivity and low loss microwave dielectrics suitable for 5G resonators and low temperature co-fired ceramic architecture

Bi₂(Li_0.5Ta_1.5)O₇ + xBi₂O₃ (x = 0, 0.01 and 0.02) ceramics were prepared using a solid state reaction method. All compositions were crystallized in a single Bi₂(Li_0.5Ta_1.5)O₇ phase without secondary peaks in X-ray diffraction patterns. Bi₂(Li_0.5Ta_1.5)O₇ ceramics were densified at 1025 °C with a permittivity (ϵ_r) of ∼ 65.1, Q_f ∼ 15500 GHz (Q ∼ microwave quality factor; f ∼ resonant frequency; 16780 GHz when annealed in O₂) and the temperature coefficient of resonant frequency (TCF) was ∼ -17.5 ppm °C^-1. The sintering temperature was lowered to ∼920 °C by the addition of 2 mol% excess Bi₂O₃ (ϵ_r ∼ 64.1, a Q_f ∼ 11200 GHz/11650 GHz when annealed in O₂ and at a TCF of ∼ -19 ppm °C^-1) with compositions chemically compatible with Ag electrodes. Bi₂(Li_0.5Ta_1.5)O₇ + xBi₂O₃ are ideal for application as dielectric resonators in 5G mobile base station technology for which ceramics with 60 < ϵ_r < 70, high Q_f and close to zero TCF are commercially unavailable. They may additionally prove to be useful as high ϵ_r and high Q_f materials in low temperature co-fired ceramic (LTCC) technology.