Excellent temperature stability on relative permittivity, and conductivity behavior of K0.5Na0.5NbO3 based lead free ceramics

Abstract

(1-x)K0.5Na0.5NbO3-xBi(Ni2/3Nb1/3)O3 [(1-x)KNN-xBNN] (x = 0.005, 0.0075, 0.01, 0.0125, 0.015) and (1-x)K0.5Na0.5NbO3-xBi(Ni0.75W0.25)O3 [(1-x)KNN-xBNW] (x = 0.005, 0.01, 0.015, 0.02) ceramics were prepared successfully via the conventional solid-state sintering method. The phase structure, dielectric properties, and conductivity behavior of ceramics were investigated. X-ray diffraction (XRD) patterns showed that both KNN-BNN and KNN-BNW had formed the solid solutions. The sintering behavior and dielectric properties could be enhanced with adding BNN and BNW. When x = 0.01, 0.99KNN-0.01BNN ceramics exhibited good properties with high relative permittivity εr of ∼1657, small Δε/ε132 °C ≤ ± 10% from 132 °C to 346 °C, low dielectric loss tanδ ≤0.037 from 132 °C to 415 °C. And for (1-x)KNN-xBNW, when x = 0.01, the excellent performances with εr of ∼1590, Δε/ε140 °C ≤ ± 15% from 140 °C to 350 °C, tanδ ≤ 0.04 from 140 °C to 411 °C were obtained in ceramics. The conductivity behavior shows that the defects and oxygen vacancies in material would provide the moving passage of a carrier.