Different p-Block Elements Induce C3[111] Octahedral Distortion on Titanium to Generate Intense Nonlinear Effect

Abstract

Acentric crystalline materials are the cornerstone of numerous cutting-edge technologies and have been highly sought-after, but they are difficult to construct controllably. Herein, by introducing a new p-block element to break the symmetrical environment of the d0 transition metal in the centric matrix TiTe3O8, a novel acentric tellurite sulfate, namely Ti(TeO3)(SO4), was successfully constructed. In its structure, two types of p-block element-centered oxo-anionic groups, i.e. [TeO3] and [SO4], induce [TiO6] an out-of-center distortion along the local C3[111] direction, which is rare in titanium oxides containing lone-pair cation. The synergy of distorted [TiO6] octahedron, lone-pair [TeO3] pyramid and rigid [SO4] tetrahedron within its structure induces a strong second harmonic generation (SHG) response of 11.6×KDP (KH2PO4), the largest value among mercury-free sulfates. Additionally, Ti(TeO3)(SO4) also shows the largest birefringence (0.145) among sulfates possessing SHG response of more than ten times of KDP, showing huge potential as a nonlinear optical material. The successful implementation of the strategy of inducing intra-octahedral distortion in d0 transition metal by different p-block elements provides new opportunities for constructing acentric structures and exploiting outstanding nonlinear optically active sulfates.