Microstructure, Enhanced Relaxor-Like Behavior and Electric Properties of (Ba 0.85 Ca 0.15 )(Zr 0.1− x Hf x Ti 0.9 )O 3 Ceramics

(Ba 0.85 Ca 0.15 )(Zr 0.1− x Hf x Ti 0.9 )O 3 (BCZHT) ceramics were fabricated by a conventional solid-state reaction method. The effects of Hf 4+ on microstructure and electric properties of BCZHT ceramics have been systematically investigated. The x-ray diffraction (XRD) results indicate that the introduction of Hf 4+ in BCZHT ceramics induces phase transition from an orthorhombic phase to the coexistence of tetragonal and orthorhombic phases, and the lattice constant decreases with the increasing of Hf 4+ content caused by substitution of Hf 4+ for Zr 4+ at B sites. As Hf 4+ content increases, the densification of BCZHT ceramics is enhanced and the grain size increases. The introduction of Hf 4+ at B sites results in the fall of the Curie temperature and the increase of dielectric constant in BCZHT ceramics. The temperature dependences of dielectric properties of BCZHT ( x = 0, 0.05 and 0.1) ceramics show obvious diffuse phase transition characteristics, and the diffuseness of phase transition is enhanced with increasing of Hf 4+ content. But there is no frequency dispersion phenomenon in BCZHT ( x = 0, 0.05 and 0.1) ceramics. The substitution of Hf 4+ for Zr 4+ at B sites of BCZHT ceramics makes its remnant polarization increase, which results from the interaction of increased grain size and tolerance factor. When temperature is above its Curie temperature, the polarization–electric field curves of BCZHT ( x = 0, 0.05 and 0.1) ceramics still show nonlinear characteristics, which further proves that there is diffuse phase transition and relaxor-like behavior. Moreover, the piezoelectric coefficient of BCZHT ceramics increases as Hf 4+ content increases.