Abstract:

The dense Bi_1.4Sc_0.1ZnNb_1.5-xRu_xO₇ ceramics were prepared by traditional solid state reaction. The effect of Sc³⁺ and Ru⁴⁺ co-substitution on the phase structure, crystal chemistry and dielectric properties of Bi₂O₃-ZnO- Nb₂O₅ were investigated. The results reveal that all doped samples show a pure α-BZN phase structure. When x=0.055 mol, the intensity of X-ray diffraction becomes weak and diffraction peaks broaden. With the increase of x, the lattice constant a and the average distance R_(A-O') of the ceramics decrease. The bond valance calculation show that the AV(O')[A₄] and oxygen ξ parameter of 48f(O) increase, but the AV(O)[A₂B₂] gradually decreases with the amount of Ru⁴⁺ increasing. Meanwhile, the dielectric constant of samples decreases and the dielectric loss increases. The dielectric relaxation characteristics are weakened at room temperature while the relaxation behavior at low temperature is obvious. With increasing dopant, T_m shifts toward higher temperature. The ε_r-T curves of samples are fitted by the modified Curie-Weiss’s (C-W) formula. The calculations show that the degree of dielectric relaxation (γ) decreases from 1.57 to 1.33 when the Ru⁴⁺ content increases from 0 to 0.04 mol.

Key words: α-BZN, oxygen parameter ξ at 48f site, modified Curie-Weiss’s formula, dielectric relaxation