ZnTeMoO6: a strong second-harmonic generation material originating from three types of asymmetric building units

Abstract

A transparent ZnTeMoO₆ crystal with dimensions of ∼12 × 10 × 1 mm³ has been successfully grown using the flux method. Single-crystal X-ray diffraction analysis reveals that ZnTeMoO₆ features a neutral layered structure consisting of three types of asymmetric building units, i.e. TeO₄ polyhedra with a stereoactive lone pair, MoO₄ tetrahedra, and ZnO₆ octahedra with a large polar displacement. The ZnTeMoO₆ crystal is non-hygroscopic, and resistant to diluted HNO₃ aqua-solution. It is also thermally stable up to 669 °C and thereafter melts incongruently. Transmittance spectra of ZnTeMoO₆ show a broad transparent window in the range of 350 nm–5.4 μm. On the basis of the powder second-harmonic generation (SHG) measurements, ZnTeMoO₆ is type-I phase-matchable with a very strong SHG efficiency of ∼10.5 × KDP. Furthermore, calculations on the dipole moments indicate that the strong SHG response may arise from the high polarizability of the three types of asymmetric building units.