Temperature coefficient-adjustable dielectric ceramics near the nominal composition Ba2Ti3Nb4O18

Dense dielectric ceramics with the nominal composition Ba2Ti3Nb4O18 were obtained by solid-state reaction. Although the XRD results showed the single phase in Ba2Ti3Nb4O18, the micro-structural analysis confirmed the existence of the secondary phase Ba3Ti4Nb4O21. Excellent temperature-stable dielectric ceramics were obtained with the nominal composition Ba2Ti3Nb4O18, where ɛr = 38, tan δ ∼ 0.0003, and τɛ ∼ 2 ppm/°C (all measured at 1 MHz). The τɛ value can be adjusted from −6 to 17 ppm/°C near the vicinity of nominal composition Ba2Ti3Nb4O18 by changing the Ti content. The microwave dielectric properties of the nominal composition Ba2Ti3Nb4O18 were as follows: ɛr = 38.1, Qf = 14,227 GHz, and τf = −11 ppm/°C.