Phase structure, Raman spectroscopic, microstructure and dielectric properties of (K_(0.5)Na_(0.5))NbO_3-Bi(Li_(0.5)Nb_(0.5))O_3 lead-free ceramics

摘要

(1-x)(K0.5Na0.5)NbO3-xBi(Li0.5Nb0.5)O-3 [(1-x)KNN-xBLN, 0 <= x <= 0.02] dielectric ceramics were synthesized by an ordinary sintering technique. The effects of Bi(Li0.5Nb0.5)O-3 addition on the phase structure, microstructure and dielectric properties of KNN ceramics were studied. The phase structure of ceramics shifted from the orthorhombic to pseudo-cubic phase structure with increasing the content of Bi(Li0.5Nb0.5)O-3. The addition of Bi(Li0.5Nb0.5)O-3 depressed the transition temperature of the orthogonal and tetragonal phases, which is a benefit to the thermal stability of KNN ceramics. Especially, as x = 0.01, the ceramics have a high relative permittivity epsilon(r) (similar to 1557), low dielectric loss tan delta (< 2.4%) and good thermal stability Delta epsilon/epsilon(150 degrees C) (<= +/- 10%) from 150 degrees C to 365 degrees C. Especially, when x = 0.005, the piezoelectric constant d(33) was improved to 133 pC/N. Furthermore, the comprehensive properties of (1-x)KNN-xBLN (0 <= x <= 0.02) ceramics were enhanced significantly to those of pure KNN ceramics. These results indicate that these ceramics could be considered as the prominent promising candidates for high-temperature capacitor application.