Fabrication and topchemical transformation mechanism of PbTiO3 microplatelets

Abstract

Two-dimensional platelets of the perovskite-structured PbTiO3 were synthesized from a layer-structured PbBi4Ti4O15 precursor, using a topochemical microcrystal route. The PbBi4Ti4O15 precursor showed a high aspect ratio with an average size of ∼7.74 μm and thickness of ∼0.29 nm. Later, PbTiO3 platelets coexisting with Pb4Bi4Ti7O24 mesophase were obtained, which had a more stable Aurivillius structure and was difficult to completely convert to the perovskite structure during topochemical microcrystal conversion. The reason that the Pb4Bi4Ti7O24 mesophase coexisted in PbTiO3 platelets was deeply discussed. Both the crystal structure difference between the unit cell parameters for (Pb4Bi2Ti7O22)2- and the thickness for the (Bi2O2)2+ layer, and the stability of (Bi2O2)2+ layer were used to analyze the existence of Pb4Bi4Ti7O24 phase. However, the result showed that the stability of (Bi2O2)2+ layer was the dominant reason, because the [OBi4]/[OPb4] tetrahedron formed in the (Bi2O2)2+ layer due to the similar chemical properties of Pb2+ and Bi3+. The work provided deep theoretical guidance to fabricate anisotropic perovskite platform-based topchemical microcrystal conversion mechanisms.