Titanium Iodates with a Second-Harmonic-Generation Response

Nonlinear-optical (NLO) crystal is an important photoelectric functional material. In this work, a new NLO titanium iodate, (H3O)2Ti(IO3)6, along with Ti(IO3)4 has been synthesized under facile conditions. The space group of (H3O)2Ti(IO3)6 is the chiral noncentrosymmetric group R3 (No. 146), with an interesting three-dimensional framework, while that of Ti(IO3)4 is the centrosymmetric space group P1̅ (No. 2) containing one-dimensional chains. Thermogravimetric analysis shows that (H3O)2Ti(IO3)6 and Ti(IO3)4 have no weight loss below 220 and 390 °C, respectively. In addition, (H3O)2Ti(IO3)6 not only is thermally stable up to 200 °C in an air atmosphere but also is stable in water. (H3O)2Ti(IO3)6 has a moderate-intensity second-harmonic-generation (SHG) response (1.4×KDP), a large laser-induced damage threshold (46×AgGaS2), and high transmittance in the wavelength ranges of 0.5–1.4 and 2.5–10 μm. Both local dipole moment and systematic theoretical calculations reveal that the SHG response of (H3O)2Ti(IO3)6 is mainly because of the combined effect of [TiO6] octahedra and IO3 and IO4 units. In a word, (H3O)2Ti(IO3)6 exhibits good NLO performances, as well as water resistance and facile growth of a single crystal with high quality, indicating its potential application as NLO materials in the visible and mid-IR regions, especially the visible region.