MgTeMoO6: A neutral layered material showing strong second-harmonic generation

Abstract

A noncentrosymmetric (NCS) compound, MgTeMoO₆, has been synthesized using the high temperature solution method with TeO₂–MoO₃ mixture as a flux. MgTeMoO₆ crystalizes in the orthorhombic space group P2₁2₁2 (No. 18) with cell parameters a = 5.03780(10) Å, b = 5.26910(10) Å, c = 8.8985(2) Å, and Z = 2. The compound exhibits a novel neutral layered structure consisting of asymmetric MgO₆ octahedra, TeO₄ polyhedra and MoO₄ tetrahedra. Thermal stability measurements revealed an incongruent melting point of 682.35 °C. The crystal exhibits a very broad transmission range from 360 nm to 5.2 μm. Powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicates that the crystal exhibits a strong SHG efficiency of ∼1.5 × KTiOPO₄. Additional SHG measurements indicate the material is type-I phase-matchable. Furthermore, calculations on the local dipole moment indicates that the strong SHG response of MgTeMoO₆ is mainly caused by the three types of NLO-active units (TeO₄, MoO₄ and MgO₆).