Two Tellurium(IV)-Based Sulfates Exhibiting Strong Second Harmonic Generation and Moderate Birefringence as Promising Ultraviolet Nonlinear Optical Materials.

Two tellurium(IV)-based sulfate nonlinear optical (NLO) materials, TeO(SO) and Te(OH)(SO)·HO, were successfully synthesized via the mild hydrothermal method. TeOSO has a two-dimensional (2D) structure consisting of [TeO] layers as well as [SO] groups. Te(OH)(SO)·HO features a simple 0D structure made up of an isolated [TeO] pyramid and a [SO] tetrahedra. Both of them are phase-matching materials and show remarkable powder second harmonic generation (SHG) efficiencies about 6 and 3 times that of KHPO (KDP), respectively, for TeOSO and Te(OH)(SO)·HO. Especially for Te(OH)(SO)·HO, in addition to a large SHG response, it possesses a short UV cutoff edge (∼233 nm) as well as moderate birefringence (0.052@546.1 nm). Furthermore, theoretical calculations confirmed that their strong SHG effects are due to the synergistic effect of the [TeO] pyramid and [SO] tetrahedra.