Role of mechanochemical activation in tuning the dielectric and relaxor-like behavior of (1− x )BCZT − x NBT ceramics

A comparative study of the dielectric properties of bulk ceramics of the (1−x)Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 − xNa 0.5 Bi 0.5 TiO 3 system, obtained by conventional sintering and by mechanical activation prior to sintering, was performed. All samples exhibited a virtually single-phase pseudocubic structure, as determined by X-ray diffraction. It is shown that mechanical activation increases the cell volume and enhances compositional homogeneity. Lattice distortion is most pronounced along the <111> direction, whereas the <110> direction exhibits the highest stability against mechanical activation. The dielectric characteristics were measured as a function of temperature in the frequency range 20 Hz to 1 MHz. All samples exhibited relaxor-like dielectric behavior, characterized by a diffuse dielectric response resulting primarily from static structural disorder. In all samples treated by mechanical activation, the maximum permittivity increased compared with that of non-activated samples. The largest increase was observed for the composition with 0.75 mol.% Na 0.5 Bi 0.5 TiO 3 . The diffuseness parameter γ of the phase transition ranged from 1.76 to 1.95 for all samples. It is shown that mechanical activation promotes a decrease in γ with increasing Na 0.5 Bi 0.5 TiO 3 content, which is attributed to increased ordering of the crystal structure.