Topochemical transformation of single crystalline SrTiO3 microplatelets from Bi4Ti3O12 precursors and their orientation-dependent surface piezoelectricity

Abstract

Two-dimensional multifunctional perovskite microcrystals are very important for various applications due to their unique shape-dependent properties. In this work, we reported a facile topochemical approach to synthesize SrTiO₃ perovskite microplatelets with remarkably improved characteristics from Aurivillius Bi₄Ti₃O₁₂ precursors. A stable Bi-containing intermediate phase was not formed during the Aurivillius to perovskite structure transformation, which facilitates the achievement of high phase/composition purity in the product and is easier than many previously reported topochemical reactions for perovskites. Different from the polycrystalline nature of the converted perovskites as reported previously, secondary recrystallization healed the substantial microstructural/crystalline damage induced during structural conversion, retaining the single-crystal memory of Bi₄Ti₃O₁₂ in the converted SrTiO₃ particles. Benefiting from subsequent epitaxial growth and rearrangement via Ostwald ripening, the SrTiO₃ microplatelets exhibited more regular shapes and narrower size distributions than the precursors, instead of only closely resembling the precursor morphologies as reported previously. For the first time, local piezoelectricity was detected from the individual SrTiO₃ microplatelets using a piezoelectric force microscope. In particular, the piezoelectric response parallel to the [001] direction was much higher than that detected perpendicular to it, possibly being associated with the orientation-dependent surface flexoelectric effect. This work offers a facile in situ topochemical strategy for fabricating other two-dimensional perovskite microcrystals and opens the door to expanding the potential application fields of SrTiO₃ microplatelets.