Barium titanate-based bilayer functional coatings on Ti alloy biomedical implants

Abstract

Piezoelectric coatings have the ability to functionalise conventional structural materials into responsive devices. Today, piezoelectric coatings have been applied to both rigid and flexible substrates for sensing, actuating, and energy harvesting applications. We envision (Ba,Ca)(Zr,Ti)O3 (BCZT) piezoelectric coatings for biomedical use such as in vivo sensing or electrical cell stimulation. However, reliable processing routes for the development of BCZT ceramics as a functionalisation coating on biomedical substrates are required. In this work, the synthesis of bilayer BCZT and CaTiO3 ceramic coatings on Ti6Al4V metal substrates via spray-deposition and heat-treatment was investigated. For thin coatings, reactions at the metal/ceramic interface led to the development of a porous interface reaction region partly consisting of CaO. The hygroscopicity of CaO affects the adhesion of the coating to Ti6Al4V at ambient conditions. Minimisation of the kinetic contributions to these interface reactions were achieved by increasing the coating thickness.