Low-Temperature Sintering and Microwave Dielectric Property of Ba_6-3xSm_8+2xTi₁₈O₅₄ Solid Solution

Abstract

Ba_6-3xSm_(8+2x)(1-y)Ti₁₈O_54-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 Ba_6-3xSm_8+2xTi₁₈O₅₄ solid solutions. Ba_6-3xSm_(8+2x)(1-y)Ti₁₈O_54-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. Ba₄Sm_9.15Ti₁₈O_53.72(x=2/3, y=0.02) ceramics sintered at 1350°C demonstrated the excellent properties including a high relative permittivity (ε_r=81), high quality factor (Q⋅f=10000GHz) and low temperature factor of resonant frequency (τ_f=-13ppm/°C). These properties are almost equivalent to those obtained in Ba₄Sm_9.33Ti₁₈O₅₄(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.