Microwave dielectric properties and microstructure of

The microstructure and microwave dielectric properties of barium samarium titanium oxide Ba_2-xSm_4+2x/3Ti_8+yO₂₄₊2_y (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 _tf 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