Electrical Properties of Na1 - xKxNbO3 (0.28 ≤ x ≤ 0.40)

Abstract

Sodium potassium niobate (Na 1 − x K x NbO 3 ) pellet samples, with x = 0.28, 0.30, 0.32, 0.325 and 0.4, were prepared by solid state reaction method. In the XRD patterns a break in the peak shifting tendency was observed for the composition with x = 0.32. Dielectric constant, loss tangent and dielectric conductivity of the prepared samples were measured in the frequency range from 10 to 1000 KHz, and in the temperature range from 30 to 500°C. Transition temperatures determined from the dielectric constant measurements were found independent of the measured frequencies, and no relaxator type behavior was observed for the presently prepared compositions. Dielectric constant and loss tangent were observed decreasing, and dielectric conductivity increasing with increasing frequency. Weak loss tangent anomalies were observed, near the transition temperatures. Transition anomalies observed from the dielectric conductivity measurements were consistent with those from the dielectric constant measurements. Among the prepared compositions dielectric constant, loss tangent and dielectric conductivity were observed minimum for Na 0.68 K 0.32 NbO 3 , at different frequencies and temperatures, which indicate a strong composition dependence of the electrical properties. Among the prepared n-type Na 1 − x K x NbO 3 compositions, an increase in the Na site vacancies and structural anomaly may be held responsible for the observed minimum dielectric conductivity of the composition with x = 0.32.