Microwave Dielectric Properties of (Ba_0.7Sr_0.3)_4.8(Sm_1-βLa_β)_8.8Ti₁₈O₅₄(β=0.1-0.5)Ceramics

Microwave dielectric ceramics of (Ba0.7Sr0.3)4.8(Sm1-βLaβ)8.8Ti18O54(β=0.1-0.5)were prepared by solid reaction method.The phase composition,microstructure and microwave dielectric properties were investigated.The results show that a single column solid solution with perovskite-like tungsten bronze structure was observed in (Ba0.7Sr0.3)4.8(Sm1-βLaβ)8.8Ti18O54 ceramics when β≤0.4.A secondary phase of BaTi6O13 appeared when β>0.4.The dielectric constant εr and the temperature coefficient τf of resonant frequency monotonically increased with increasing La3+ content.The β-value exhibited a negative effect on quality factor.Optimal microware dielectric properties were achieved in the ceramic as the β=0.4 with εr of 100.23,Qf of 5 110 GHz and τf of 19.3×10-6/℃.The εr -value of the ceramic was better than that of Ba6-3xSm8+2xTi18O54 ceramic.And the temperature coefficient of resonant frequency was near zero.