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

Bi 2 (Li 0.5 Ta 1.5 )O 7 + xBi 2 O 3 (x = 0, 0.01 and 0.02) ceramics were prepared using a solid state reaction method. All compositions were crystallized in a single Bi 2 (Li 0.5 Ta 1.5 )O 7 phase without secondary peaks in X-ray diffraction patterns. Bi 2 (Li 0.5 Ta 1.5 )O 7 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 O 2 ) 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 Bi 2 O 3 (ϵ r ∼ 64.1, a Q f ∼ 11200 GHz/11650 GHz when annealed in O 2 and at a TCF of ∼ -19 ppm °C -1 ) with compositions chemically compatible with Ag electrodes. Bi 2 (Li 0.5 Ta 1.5 )O 7 + xBi 2 O 3 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.