Morphotropic phase boundary in Na1−xKxNbO3, near x=0.32x=0.32

Pellet samples of Na1−xKxNbO3 with x=0.28x=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)(x), a break was observed in the X-ray diffraction peaks shifting tendency; a slope change anomaly in the a/ba/bvs  . xx 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=0.32x=0.32. The observed minimum values of dielectric parameters may be associated with the increased Na-site vacancies and structural anomaly, at x=0.32x=0.32.