Microwave dielectric properties of Ba 2− xSm 4+2/3 xTi 9O 26 ceramics with zero temperature coefficient

Abstract

Ba 2− x Sm 4+2 x/3 Ti 9O 26 ( x=0–0.3) was selected as the formula for BaO–Sm 2O 3–4.5TiO 2 ceramics based on the structure formula of the tungsten–bronze-type structure. The microstructure and microwave dielectric properties of Ba 2− x Sm 4+2 x/3 Ti 9O 26 and the relationships between them were investigated in this study. The microstructure of Ba 2− x Sm 4+2 x/3 Ti 9O 26 ceramics consists of a uniform matrix of primary BaO–Sm 2O 3–4TiO 2 and BaO–Sm 2O 3–5TiO 2 with small amounts of dispersed second phase, TiO 2 and Ba 2Ti 9O 20. Excellent dielectric properties of ε r=68–79, Q× f=11 000–12 500 GHz and good temperature stability at the resonant frequency ( τ f=0 ppm per °C) were obtained. The relationships between the microstructure, second phases and microwave dielectric properties were concerned. XRD patterns, energy dispersive X-ray spectrometer (EDS) analysis and scanning electron microscopy are also presented.