Temperature dependent dielectric properties of (na, K) NbO3, near equimolar composition

Abstract Pellet samples of Na1-xKxNbO3 (0.490 ≤ x ≤ 0.510) were prepared using solid state reaction method with double sintering. Dielectric measurements were carried out on the prepared samples, from 30 to 500 °C, at 1 MHz. Dielectric constant and electrical conductivity were found minimum, for x = 0.500 among all the prepared compositions, at room temperature and at all the measured frequencies. Three distinguished phase transitions, at 200, 380 and 460 °C, were observed in dielectric measurements of the prepared compositions. The high temperature X-ray diffraction (HT- XRD) of the samples with x = 0.500, shows monoclinic phase between room temperature and 200 °C, tetragonal between 200 and 380 °C, tetragonal with increased lattice parameters, between 380 and 460 °C, and cubic phase beyond 460 °C. The tetragonal to tetragonal phase transition at 380 °C, and tetragonal to cubic at 460 °C was distinctly observed from dielectric and HT- XRD measurements in the present study.