Crystal structures, phase stability, and dielectric properties of (1−x) Bi3/2MgNb3/2O7−x Bi2Zn2/3Nb4/3O7 ceramics

The preparation, crystal structures, phase stability and dielectric properties of the (1−x) Bi3/2MgNb3/2O7−x Bi2Zn2/3Nb4/3O7 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) ceramics were investigated systematically. The sol-gel process was employed to produce crystalline, single-phase Bi1.5Mg1.0Nb1.5O7 (BMN) and Bi2(Zn2/3Nb4/3)O7 (β_BZN) pre-nanopowders for the synthesis of the ceramics. X-ray diffraction data indicated that these ceramics presented a phase transition for Bi3+ and Zn2+-rich specimens (x ⩾ 0.6), from cubic pyrochlore to orthorhombic zirconolite-like structure. The tolerance factor (t) combined with rA/rB value and the lattice energy (U) were employed to provide an indication of the structural stability of the (1−x) BMN-x β_BZN cubic pyrochlores (x ⩽ 0.4). The tolerance factor (t) calculation contain more structural information, which gives further insight into the details of the structural stability features in the (1−x) BMN-x β_BZN cubic pyrochlores. The relationships between the crystal structures and dielectric properties of the ceramics were determined, and the dielectric loss was related to the phase stability of the system. It is suggested that the dielectric properties are mainly determined by the phase structure, composition and stability in the (1−x) BMN-x β_BZN system.