Phase evolution, dielectric and conductivity behaviors of (K0.5Na0.5)NbO3–La(Zn0.5Zr0.5)O3 ceramics

(1 −  x )K 0.5 Na 0.5 NbO 3 – x La(Zn 0.5 Zr 0.5 )O 3 [(1 −  x )KNN– x LZZ, x  = 0.005, 0.010, 0.015, 0.020] ceramics were synthesized to fulfill the application requirement of high-temperature ceramic capacitors. The influence of LZZ content on the phase structure, microstructure morphology, dielectric and conductivity behaviors of this system was conducted. An orthorhombic phase for 0.005 ≤  x  ≤ 0.010 and an orthorhombic-tetragonal coexisting phase for 0.015 ≤  x  ≤ 0.020 were determined by the X-ray diffraction, Rietveld refinement, and dielectric spectra. The ceramic with x  = 0.015 exhibits an ultrahigh and stable permittivity ( ε'  ~ 1892, ± 15% variation) and a low dielectric loss (tan δ  ≤ 0.05) in a wide temperature region of 82–382 °C owing to the composition heterogeneity-induced shoulder-like peak and diffuse phase transition from tetragonal to cubic. The activation energies from the high-temperature dielectric relaxation and conductivity behaviors initially enhance greatly and then increase slowly, which could be related to the synergy effect of decreased oxygen vacancies and microstructure morphology evolution.