Effect of sintering temperature on the microstructural, dielectric, ferroelectric and piezoelectric properties of (Na0.5K0.5)NbO3 ceramics prepared from nanoscale powders

(Na0.5K0.5)NbO3 nanoscale powders of average particle size of about 35 nm were obtained by high energy ball milling and sintered at 1050 °C, 1080 °C and 1110 °C for 1 h. A crossing over in the values of internal strains η011 and η100, as well as in the values of lattice parameters ‘b’ and ‘c’ was observed as the sintering temperature increases from 1080 to 1110 °C, indicating the occurrence of some structural transformation of the crystal within this temperature range. The ceramic sample sintered at 1080 °C was found to possess the highest values of lattice strain, crystallite size, grain size, room temperature dielectric constant (ɛ′rt), remnant polarization (Pr), piezoelectric charge constant (d33) and electromechanical coupling factor (kp). The dielectric response to frequency for this sample remains almost unchanged over a wide frequency range. d33 and kp values as high as 126 pC/N and 0.47 respectively were obtained for the same sample. The present work reveals the sensitivity of various properties of (Na0.5K0.5)NbO3 ceramics prepared from nanoscale powders on sintering temperature.