Dielectric behavior and impedance analysis of lead-free CuO doped (Na0.50K0.50)(0.95)(Li0.05Sb0.05Nb0.95)O-3 ceramics

Abstract

Pure (Na0.50K0.50)(0.95)(Li0.05Sb0.05Nb0.95)O-3 (NKNLS) and CuO doped NKNLS perovskite structured ferroelectric ceramics were prepared by the solid-state reaction method. x wt% of CuO (x = 0.2-0.8 wt%) was added in the NKNLS ceramics. X-ray diffraction patterns indicate that single phase was formed for pure NKNLS while a small amount of second phase (K6Li4Nb10O30 similar to 3%) was present in Cu2+ doped NKNLS ceramics. Dielectric anomalies around the temperatures of 120 degrees C and 350 degrees C have been identified as the ferroelectric-paraelectric transition (orthorhombic to tetragonal and tetragonal to cubic) temperatures for pure NKNLS compound. The electrical behavior of the ceramics was studied by impedance study in the high temperature range. Impedance analysis has shown the grain and grain boundary contribution using an equivalent circuit model. The impedance response in pure and Cu2+ doped NKNLS ceramics could be resolved into two contributions, associated with the bulk (similar to grains) and the grain boundaries. From the conductivity studies, it is found that activation energies are strongly frequency dependent. The activation energy obtained from dielectric relaxation data may be attributed to oxygen ion vacancies. (C) 2012 Elsevier Masson SAS. All rights reserved.