Effect of sintering temperature on composition, microstructure and electrical properties of K sub(0.5)Na sub(0.5)NbO sub(3) ceramics

Lead free potassium sodium niobate (K sub(0.5)Na sub(0.5)NbO sub(3)) ceramic powders were synthesized by colloidal coating method. The calcined powders (800 [degrees]C) were sintered conventionally at three different temperatures (1050 [degrees]C, 1100 [degrees]C and 1150 [degrees]C) and the effect of sintering temperature on density, microstructure, composition and electrical properties was investigated. All the samples showed a single phase perovskite structure with orthorhombic symmetry similar to KNbO sub(3) ceramics. Microstructure examined under FEG-SEM revealed an optimum microstructure, in terms of grain size, porosity and uniformity, at the sintering temperature of 1100 [degrees]C which also showed density of 92% of [rho] sub(Th). As the sintering temperature increased the X-ray diffraction peaks shifted to lower 2[theta] values indicating excess volatilization of Na at higher temperature as compared to K. This was further confirmed through elemental Probe X-ray microanalysis and ICP-AES studies. Dielectric constant ([epsilon] sub(r)), dielectric loss (tan[delta]), ferroelectric (P-E loop) and piezoelectric (d sub(33)) properties showed considerable improvement and leakage current decreased with increasing sintering temperature. The sample sintered at 1100 [degrees]C showed marked improvement in maximum dielectric constant (573) at RT at 1 kHz, minimum tangent loss (0.04) at RT at 1 kHz, maximum remnant polarization (13.5 [mu]C/cm super(2)), lower leakage current (7.6 x 10 super(-7) A/cm super(2)) and maximum d sub(33) value (100pC/N).