Morphotropic phase boundary in , near

Pellet samples of Na 1 − x K x NbO 3 with x = 0.28 , 0.30, 0.32, 0.325 and 0.40 were prepared by a solid state reaction method. X-ray diffraction and dielectric measurements were carried out on the prepared samples. With varying composition ( x ) , a break was observed in the X-ray diffraction peaks shifting tendency; a slope change anomaly in the a / b vs. x plot; and minimum values of dielectric constant, loss tangent and dielectric conductivity, at all the measured frequencies and temperatures, showing a strong compositional dependence of structural and dielectric properties — a morphotropic phase transition, at x = 0.32 . The observed minimum values of dielectric parameters may be associated with the increased Na-site vacancies and structural anomaly, at x = 0.32 .