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

In this work, piezoceramics of (1−x)(Bi0.5Na0.5)TiO3–x(K0.5Na0.5)NbO3, (1−x)BNT–xKNN, in the compositional range 0.00 ≤ x ≤ 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 (i.e., from a perspective of its intrinsic properties), the microstructural evolution was strongly dependent on the content of the KNN phase (i.e., 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.