Effect of ordered structure and domain boundary on low-loss Ba[Mg1/3(Nbx/4Ta(4−x)/4)2/3]O3 microwave dielectric ceramics

The microstructure of Ba[Mg1/3(NbxTa(4−x)/4)2/3]O3 ceramics (x = 1, 2, 3, and 4) was investigated. Ordered structure and domain boundary were observed by high-resolution transmission electron microscopy. The disordered structure of 0.41 nm lattice modulation and the 1:2 ordering structure of 0.71 nm lattice modulation in the [111] direction are both formed in Ba[Mg1/3(NbxTa(4−x)/4)2/3]O3 ceramics. Except for the incoherent interface between disordered and 1:2 ordering domain, the coherent interface between two 1:2 ordering domains can also be observed in the Ba[Mg1/3(NbxTa(4−x)/4)2/3]O3 ceramics. In the Ba[Mg1/3(Nb1/4Ta3/4)2/3]O3 ceramic, the formation of an extra ordering structure (lattice modulation of 1.24 nm in the [111] direction) on the antiphase domain boundary with proper Nb substitution contributes to lower dielectric loss due to the stabilization of the domain boundary.