The primary objective of this research is the synthesis and characterization of new second-harmonic generating (SHG) oxide materials, as well as to understand the associated structure-property relationships. A symmetry requirement for second-harmonic generation is crystallographic noncentrosymmetry. In order to enhance the incidence of noncentrosymmetry in any new oxide material, cations that undergo second-order Jahn-Teller distortions were utilized. These cations, d0 transition metals (Ti4+, Nb5+, W6+, etc.) and cations with lone-pairs (Se4+, Te4+, Sb3+, etc.), are often observed in asymmetric oxide environments. We have synthesized several noncentrosymmetric materials that contain these cations. We have investigated their nonlinear optical properties through powder SHG measurements. These experiments indicate that the SHG efficiency is dependent not only on the individual atomic polarizations, but more importantly on the ‘net' direction of the polarization. In addition, we have developed a structural model that allows us to determine the structural origin of the SHG response. Powder SHG data and structure-property relationships are presented and explored.
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