Low temperature preparation and electric properties of highly (100)-oriented (Na0.85K0.15)0.5Bi0.5TiO3 thin films prepared by a sol–gel route

Abstract

Lead-free (Na0.85K0.15)0.5Bi0.5TiO3 thin films with different spin-coating layers were fabricated by a sol–gel process using a 15nm-thick Pb0.8La0.1Ca0.1Ti0.975O3 seed layer. The phase composition and electrical properties of the thin films were investigated in detail. X-ray diffraction analysis indicated that low-temperature growth of (Na0.85K0.15)0.5Bi0.5TiO3 thin films—as low as 500°C—was successfully achieved. The films, comprising six layers, featured both rhombohedra and tetragonal phases near the morphotropic phase boundary. In contrast, the films fabricated with 9 and 12 layers consisted of single phase only. Additionally, a slow interfacial diffusion was achieved, owing to the low crystallization temperature. The six-layer thin film that crystallized at a low temperature exhibited enhanced electrical properties when the external electric field was small, which was attributed to the co-existence of multiple phases and an unhindered interface.