SnTiO₃ MATERIAL, METHOD OF PREPARATION THEREOF, USE THEREOF AS FERROELECTRIC MATERIAL AND DEVICE COMPRISING A FERROELECTRIC MATERIAL

摘要

The present invention relates to a material of the formula SnTiO₃ having a crystal structure comprised of layers, wherein the layers comprise Sn(II) ions, Ti(IV) ions and edge-sharing O₆-octahedra, the edge-sharing O₆-octahedra form a sub-layer, the Ti(IV) ions are located within 2/3 of the edge-sharing O₆-octahedra, thus forming edge-sharing TiO₆-octahedra, the edge-sharing TiO₆-octahedra form a honeycomb structure within the sub-layer, the honeycomb structure comprising hexagons with Ti(IV)-vacancies within the hexagons, the Sn(II) ions are located above and below the Ti(IV)-vacancies with respect to the sub-layer, the Ti(IV) ions are optionally substituted with M, M is one or more elements selected from Group 4 and Group 14 elements, and the crystal structure satisfies at least one of the following features (i) and (ii): (i) the Sn(II) ions have a tetrahedral coordination sphere involving three O ions of the layer and the electron lone pair of the Sn(II) ions which is situated at an apical position relative to the three O ions of the layer, (ii) the layers are stacked so that each layer is translated relative to each adjacent layer by a stacking vector S1 or a stacking vector S2, the centers of adjacent hexagons form a parallelogram with a side having a length x and side having a length y, the stacking vector S1 is a combined translation along the side having the length x by 2/3 x and along the side having a length y by 1/3 y, the stacking vector S2 is a combined translation along the side having the length x by 1/3 x and along the side having a length y by 2/3 y, and the crystal structure comprises layers translated relative to adjacent layers by the stacking vector S1 and layers translated relative to adjacent layers by the stacking vector S2. The present invention is further directed to a material of the formula SnTiO₃ having a tetragonal perovskite-type crystal structure, a method for the preparation of SnTiO₃, a device comprising a ferroelectric material and a use of the material of the formula SnTiO₃ in a ferroelectric element.