MnO_2-modified 0.98(K_(0.5)Na_(0.5))NbO_3-0.02LaFeO_3 ceramics with low dielectric loss for high temperature ceramics capacitors applications

摘要

The MnO_2-doped 0.98(K_(0.5)Na_(0.5))NbO_3-0.02LaFeO_3 [0.98KNN-0.02LF-x] lead-free ceramics were prepared by the conventional solid-state sintering method. The effects of MnO_2 doping on the phase structure, microstructure, and electrical properties of the ceramics were investigated. The results reveal that MnO_2 is an excellent sintering aid for the 0.98KNN-0.02LF-x ceramics to improve the densification and decrease the sintering temperature. Additionally, the MnO_2 doping significantly increases the dielectric permittivity and decreases the dielectric loss of the 0.98KNN-0.02LF ceramics. The 0.98KNN-0.02LF-1.5 mol% ceramics show excellent high temperature dielectric properties: the dielectric permittivity ε_r is approximately 2000 and dielectric loss tgδ is smaller than 3% at a broad temperature range from 100 to 400 ℃.