Structural stability and electrical properties of (1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 ceramic coatings

Abstract

In this paper, (1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 (x = 0, 0.06, 0.08, and 0.10) ceramic coatings were prepared by supersonic plasma spraying. Phase structure, microstructure, dielectric, ferroelectric, and piezoelectric properties of the (Bi0.5Na0.5)TiO3 ceramic coatings doped with BaTiO3 were all thoroughly examined. According to the findings, all of the (1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 ceramic coatings have a typical perovskite structure and form a morphotropic phase boundary (MPB) with rhombohedral and tetragonal phases coexisting in the x = 0.06–0.10 range. The coating's overall surface is uniformly flat, with a surface roughness (Sa) of less than 10 μm and a line roughness (Ra) of less than 2 μm. The coating has a homogeneous cross section, a well-integrated interface, a few pores and cracks, and a porosity of less than 6 %. With no obvious valence changes of the other elements, the results of XPS indicate a certain degree of breakdown during the spraying process, when Ti4+ changes to generate oxygen vacancy defects of Ti3+. The best electrical conductivity of the 0.92BNT-0.08BT coating has been found at x = 0.08, where the dielectric constant is 255 (0.02), the remnant polarization (Pr) is 22.21 μC/cm2, the coercive field (Ec) is 29.17 kV/cm, and the piezoelectric coefficient (d33) is 35.1 pC/N. The (1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 ceramic coating application space and range at high temperature are expanded when the temperature (Tm) close to the maximum dielectric constant increases significantly reaching 431.2 °C.