Effects of Ca2+ substitution on microstructure and microwave dielectric properties of low loss Ba(Mg1/3Nb2/3)O3 perovskite ceramics

Ba1-xCax(Mg1/3Nb2/3)O-3 (0x0.02) perovskite ceramics were prepared by the solid-state reaction method. The phase composition and microstructure were characterized by XRD and SEM, respectively. The result showed that all ceramics exhibited the 1:2 ordered perovskite structure, and the grain size decreased first and then increased with different substitution amount of Ca2+ for Ba2+. The dielectric properties were examined by Vector network analyzer, and the Raman spectra was used to interpret the dielectric properties of Ba1-xCax(Mg1/3Nb2/3)O-3 ceramics. The dielectric constant (epsilon(r)) were strongly depended on the Raman shift of A(1g)(O) stretch mode, and the quality factor (Qxf) manifested great correlated with the full width at half maxima (FWHM) of A(1g)(O) stretch mode. The Ba1-xCax(Mg1/3Nb2/3)O-3 ceramics substituted of Ca2+ for Ba2+ in x=0.005, which possessed the narrowest FWHM and the highest degree of 1:2 ordering, showed the best microwave dielectric properties: epsilon(r)=31.64, Qxf=74421GHz, (f)=14.59ppm/degrees C.