Ce3F4(SO4)4

Abstract

Noncentrosymmetric (NCS) structure is the paramount precondition for producing second-harmonic generation (SHG) of crystalline materials. Herein, a fluorine-enriched-induced centrosymmetric-to-noncentrosymmetric transformation strategy was employed in CS Ce2F2(SO4)3·2H2O, leading to the discovery of new NCS cerium fluoride sulfate, Ce3F4(SO4)4. Ce3F4(SO4)4 crystallizes in polar space group C2, and features a 2D-layered framework constructed from [CeO5F3] and [CeO6F2] polyhedra, extending to a final 3D framework linked via two crystallographically independent [SO4] units. Ce3F4(SO4)4 displays a phase-matchable SHG effect of about 1.0 times that of KDP and sufficient experimental birefringence (0.141@546 nm) in fluorine-containing sulfate-based NLO materials. Structural analysis and first-principle calculations suggest that the ordered arrangement of fluorinated cerium-centered polyhedra ([CeO5F3] and [CeO6F2]) as well as [SO4] tetrahedra play a significant role in SHG activity and birefringence. Our study illustrates that the introduction of metal-centered polyhedra with a high degree of fluorination is conducive to the formation of NCS structure and is a valuable method for designing novel nonlinear optical materials. Show more