Low-Temperature Sintering and Microwave Dielectric Property of Ba6-3xSm8+2xTi18O54 Solid Solution

Ba6-3xSm(8+2x)(1-y)Ti18O54-δ{δ=3y(x+4)} ceramics were developed in this study to lower the sintering temperature as well as to maintain the excellent microwave dielectric properties of tungsten-bronze-type like Ba6-3xSm8+2xTi18O54 solid solutions. Ba6-3xSm(8+2x)(1-y)Ti18O54-δ ceramics were prepared by a slight change in the mixing composition from the solid solutions area to Ba2Ti9O20 direction on the BaO-Sm2O3-TiO2 ternary phase diagram. Effects of compositional parameters x and y on the density of the sintered body and the microwave dielectric properties were investigated. Ba4Sm9.15Ti18O53.72(x=2/3, y=0.02) ceramics sintered at 1350°C demonstrated the excellent properties including a high relative permittivity (εr=81), high quality factor (Q⋅f=10000GHz) and low temperature factor of resonant frequency (τf=-13ppm/°C). These properties are almost equivalent to those obtained in Ba4Sm9.33Ti18O54(x=2/3) solid solutions which need higher fabricating temperatures than 1460°C. It was also shown that a ball-milling technique strongly affected the density of sintered body and the resulting relative permittivity.