| The high frequency microwave dielectric ceramics of complex perovskite structure Ba(Mg1/3Ta2/3)O3 type were selected as the research objects, and the specimens were prepared by the mixed oxide method. The crystal structure and dielectric properties of Ba(Mg1/3Ta2/3)O3 materials were investigated by using X-ray powder diffraction, scanning electron microscopy and the Hakki-Coleman opened resonator method. The crystal structure and dielectric properties of BMT materials were systematically investigated. The two structures of BMT main phase, that is 1:2 ordered hexagonal superlattice and disordered cubic structure reflections, were marked in XRD patterns by crystallography. A pure BMT ceramic with ε=25.42, tgδ=0.64 × 10-4,αε=-23.87 × 10-6/ ℃ , ρ v=1.4 × 1014 Ω cm,τf=1.93 × 10-6/ ℃ was obtained. The process of two-step calcinations eliminates the effect on sintering ability made by satellite phase of Ba0.5TaO3. ε=25.05, tgδ=0.22×10-4,αε=-20.01×10-6/℃,ρv=7.2×1014Ωcm,τf=0.0075×10-6/℃. The structure and dielectric properties of BMT-MC system were investigated. The sintering temperature of BMT was lowered from 1600℃ to 1480 ℃ for the first time by adding a small quantity of MnCO3, and got good dielectric properties at 0.5%: ε=25.58,tgδ=0.23×10-4,αε=-17.58×10-6/℃,ρv=1.0×1015Ωcm,τf=-1.21×10-6/℃. By addition of BaWO4,the densification temperature of BMT ceramic is as low as 1380℃ contrasted with the normal sintering temperature, and got good dielectric properties at 4%:ε=24.07,tgδ=0.4 × 10-4,αε=-7.96 × 10-6/ ℃ , ρ v=1.4 × 1015 Ωcm,τf=-6.01×10-6/℃. The microwave properties of Ba(Mg1/3Ta2/3)O3 type ceramic materials were investigated by using the Hakki-Coleman opened resonator method. The results listed follow: BMT 系,ε=24.79, Qf=143000(10.10GHz),τf=0.0075×10-6/℃; BMT-MC 系,ε=25.68,Qf=122040(10.17GHz),τf=0.15×10-6/℃; BMT-BW 系,ε=23.00,Qf=124000(10.127GHz),τf=-1.45×10-6/℃。... |
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