Fabrication and topchemical transformation mechanism of PbTiO3 microplatelets

Two-dimensional platelets of the perovskite-structured PbTiO 3 were synthesized from a layer-structured PbBi 4 Ti 4 O 15 precursor, using a topochemical microcrystal route. The PbBi 4 Ti 4 O 15 precursor showed a high aspect ratio with an average size of ∼7.74 μm and thickness of ∼0.29 nm. Later, PbTiO 3 platelets coexisting with Pb 4 Bi 4 Ti 7 O 24 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 Pb 4 Bi 4 Ti 7 O 24 mesophase coexisted in PbTiO 3 platelets was deeply discussed. Both the crystal structure difference between the unit cell parameters for (Pb 4 Bi 2 Ti 7 O 22 ) 2- and the thickness for the (Bi 2 O 2 ) 2+ layer, and the stability of (Bi 2 O 2 ) 2+ layer were used to analyze the existence of Pb 4 Bi 4 Ti 7 O 24 phase. However, the result showed that the stability of (Bi 2 O 2 ) 2+ layer was the dominant reason, because the [OBi 4 ]/[OPb 4 ] tetrahedron formed in the (Bi 2 O 2 ) 2+ layer due to the similar chemical properties of Pb 2+ and Bi 3+ . The work provided deep theoretical guidance to fabricate anisotropic perovskite platform-based topchemical microcrystal conversion mechanisms.