Effect of Firing Conditions on Phase Formation, Microstructure, and Electrical Properties of (K0.5Na0.5)(Nb0.7Ta0.3)O(3)Ceramics Synthesized by Solid-State Combustion Method

摘要

The effect of the firing conditions on the phase formation, microstructure, and electrical properties of (K0.5Na0.5)(Nb0.7Ta0.3)O-3(KNNT) ceramics synthesized by the solid-state combustion technique using glycine as fuel has been investigated. All samples were calcined at 600 degrees C to 800 degrees C for 2 h and sintered at 1150 degrees C to 1190 degrees C for 2 h to 5 h. Pure KNNT powders were produced after calcination at 600 degrees C for 2 h. The average particle size increased when the calcination temperature was increased. The KNNT powder calcined at 600 degrees C for 2 h showed rather square morphology with average particle size of similar to 160 nm. The x-ray diffraction (XRD) analysis results for the ceramics revealed the presence of orthorhombic (O) and tetragonal (T) phases in all samples. When sintering at 1150 degrees C for 4 h, the O:T ratio was 50:50, as verified by the Rietveld refinement technique. The average grain size, density values, and dielectric properties tended to increase when the dwell time was increased from 2 h to 4 h, but then degraded. The KNNT ceramic produced at the optimum firing condition (1150 degrees C for 4 h) showed good crystalline morphology, the highest density (rho = 5.28 g/cm(3)), the highest dielectric constant (epsilon(C) = 5002), and good ferroelectric behavior (P-r = 18.50 mu C/cm(2)andE(c) = 9.04 kV/cm).