Na11Ta8P7O43: (Ta8O33) bi-capped triangular prisms connected by PO4 groups resulting in a phase-matched second harmonic response

Abstract

Much effort has been devoted to synthesizing nonlinear optical crystals with efficient second harmonic responses. Herein, a tantalum phosphate crystal Na₁₁Ta₈P₇O₄₃ with a moderate second harmonic response was obtained using self-fluxes of NaH₂PO₄ and Na₂HPO₄. Na₁₁Ta₈P₇O₄₃ belongs to the Cc space group of monoclinic systems with cell parameters of a = 8.5710(2) Å, b = 15.1144(4) Å, c = 28.7712(7) Å, β = 92.304(2)°, Z = 4. Its structural features were unique (Ta₈O₃₃) bi-capped triangular prisms uniformly oriented with a PO₄ connection in the ab plane, which were further joined through additional PO₄ groups in the c direction, resulting in moderate nonlinear effects. In addition, this crystal has the characteristics of phase-matchable second harmonic generation, a shorter cutoff edge than the known materials LiTaO₃ and KTiOPO₄, and high transmittance from the visible to the near infrared band, and may serve as a potential nonlinear optical crystal.