Structure and microwave dielectric properties of (Ba1 − xSm2x/3)((Co0.7Mg0.3)1/3Nb2/3)O3 ceramics

Abstract

The sintering behavior, microstructure and microwave dielectric properties of (Ba1 − xSm2x/3)((Co0.7Mg0.3)1/3Nb2/3)O3 (0.01 ≤ x ≤ 0.04) ceramics has been investigated. A small amount of Sm-substitution facilitates the densification of Ba (Co0.7Mg0.3)1/3Nb2/3O3 ceramics. All ceramic samples are well-sintered and the relative densities are beyond 97%. Small homogeneous grains and low porosity have been observed by scanning electron microscopy photograghs. Single-phase solid solutions are achieved in all compositions and no secondary phase was detected by X-ray diffraction patterns. The appropriate amount of Sm-substitution on A-site leads to the improved degree of 1:2 B-site cation ordering, while the ordered degree decreases gradually as the Sm content increases, which is related to the A-site deficiency caused by the inequitable substitution. The degree of 1:2 ordering structure is responsible for the microwave dielectric properties of the Sm-substituted samples, especially Q × f values. A good combination of microwave dielectric properties have been obtained for (Ba0.98Sm0.04/3)((Co0.7Mg0.3)1/3Nb2/3)O3 sintered at 1420 °C: er = 32.9, Q × f = 50309 GHz and τf = 6 ppm/oC.