Dielectric properties of (K_(0.5)Na_(0.5))NbO_3-(Bi_(0.5)Li_(0.5))ZrO_3 lead-free ceramics as high-temperature ceramic capacitors

摘要

(1 - x)K0.5Na0.5NbO3-x(Bi0.5Li0.5)ZrO3 (labeled as (1 - x)KNN-xBLZ) lead-free ceramics were fabricated by a solid-state reaction method. A research was conducted on the effects of BLZ content on structure, dielectric properties and relaxation behavior of KNN ceramics. By combining the X-ray diffraction patterns with the temperature dependence of dielectric properties, an orthorhombic-tetragonal phase coexistence was identified for x = 0.03, a tetragonal phase was determined for x = 0.05, and a single rhombohedral structure occurred at x = 0.08. The 0.92KNN-0.08BLZ ceramic exhibits a high and stable permittivity (similar to 1317, +/- 15% variation) from 55 to 445 degrees C and low dielectric loss (= 6%) from 120 to 400 degrees C, which is hugely attractive for high-temperature capacitors. Activation energies of both high-temperature dielectric relaxation and dc conductivity first increase and then decline with the increase of BLZ, which might be attributed to the lattice distortion and concentration of oxygen vacancies.