Enhanced piezoelectricity in Al2O3 (0001) single crystal substrate-sintered Bi12TiO20–BaTiO3 composite ceramics

Bi₁₂TiO₂₀–BaTiO₃ bulk composite ceramics prepared by sintering a mixture of presynthesized BaTiO₃ and Bi₁₂TiO₂₀ particles around the melting point of Bi₁₂TiO₂₀ could exhibit direct as well as inverse piezoelectricity without electrical polarization. To prevent the permeation of melting Bi₁₂TiO₂₀ into a substrate and thus increase the composition gradient, samples were sintered on an Al₂O₃ (0001) single crystal substrate instead of an Al₂O₃ ceramic substrate. In this study, the Al₂O₃ single crystal substrate sintering method was surprisingly found to be an effective method to improve the piezoelectric performance of Bi₁₂TiO₂₀–BaTiO₃ ceramics. These samples showed an enhanced piezoelectric strain coefficient (d₃₃) by 80% compared to samples sintered on Al₂O₃ ceramics. Moreover, the d₃₃ value remains nearly identical over the entire surface. Combining the results of XRD, EDS, XPS, ICP and Raman spectroscopy, the improved piezoelectricity might be because of the alignment of distorted BiO₅ polyhedra in the amorphous Bi₁₂TiO₂₀ phase caused by the composition gradient. These results offer a method to enhance the piezoelectric properties of Bi₁₂TiO₂₀-based ceramics and will inspire further research to develop Bi₁₂TiO₂₀-based ceramics suitable for practical use.