Dielectric and ferroelectric properties evolution of (1−x)(Bi0.5Na0.5TiO3)–xK0.5Na0.5NbO3 piezoceramics

Abstract

In this work, piezoceramics of (1-x)(Bi0.5Na0.5)TiO3-x(K0.5Na0.5)NbO3, (1-x)BNT-xKNN, composition with x=0.01, 0.02, 0.03, 0.04, 0.05, 0.06 and 0.07 were prepared by a mechanochemically activated solid-state method. The structural phase formation and microstructural, dielectric and ferroelectric properties were studied. Although changes, in symmetry of the perovskite structure, were not detected with the composition (that is, from a perspective of its intrinsic properties), the microstructural evolution was strongly dependent on the content of the KNN phase (that is, based on its extrinsic properties). Specifically, KNN favoured the formation of a microstructure with cubic grains, typical morphology of the alkaline niobate ceramics. After KNN addition, both the maximum permittivity temperature and the long-range to short-range ordered transition temperature were reduced. Additionally, ferroelectric loops and strain deformation curves also reflect the long-range to short-range order evolution with KNN addition and temperature.