Microwave dielectric properties and microstructure of Ba2−xSm4+2x/3Ti8+yO24+2y ceramics

The microstructure and microwave dielectric properties of barium samarium titanium oxide Ba2−xSm4+2x/3Ti8+yO24+2y (x=0.1, y=0∼2) ceramics (BST) were investigated. The optimum compositions of BST ceramics were synthesized and discussed base on the structure formula of the tungsten–bronze-type crystal phase. Differential thermal analysis (DTA) was used to select the suitable sintering temperatures. The relative dielectric constant of the BST compositions saturated in a range from 63 to 85. Q×f values of 8500–13000 (GHz) were obtained for various y values in dense samples. The temperature coefficient of resonant frequency τf was adjusted from a negative −12 ppm per °C value to a positive value 17 ppm per °C. X-ray diffraction, SEM and EDS analysis were used to investigate the microstructure and correlate its relationship with microwave dielectric properties of BST ceramics