Balanced development of dielectric permittivity, loss tangent, and temperature stability in K0.5Na0.5Nb0.5O3-based ceramic capacitors

Ceramic capacitors are extremely expected to attain the high dielectric permittivity (epsilon') and low loss tangent (tan delta) stabilized in an ultra-wide operating temperature range. In this work, we improved epsilon', tans and their temperature stability by tailoring the distortion of oxygen octahedron with a different chemical composition in the K(0.5)Na(0.5)Nb(0.5)O(3-)based materials, and the relationships among the composition, crystal structure and dielectric performances were systematically investigated. By designing a series of material systems of K0.5Na0.5NbO3 {KNN-M, M: Al, Fe, (Ti0.5Mg0.5), (Ti0.5Zn0.(5)), (Nb-1/Zn-3(2/3))}, the decreased distortion of oxygen octahedron and enhanced symmetry in crystal structure could be well established, and a high dielectric permittivity (epsilon' = 1130 +/- 15%) with stability in 25 degrees C -500 degrees C range was achieved in the KNN-NbZn ceramics. Particularly, a low loss tangent (tan delta <= 3%) was maintained up to 360 degrees C in the ceramics. Therefore, a balanced development of epsilon' tan delta and their temperature stability was achieved in the KNN-NbZn materials and we consider this work will bring a clear understanding about the temperature-stable behaviors of dielectric properties in KNN-based ceramic capacitors. (C) 2019 Elsevier B.V. All rights reserved.