Na 2 CeF 6 : A Highly Laser Damage-Tolerant Double Perovskite Type Ce(IV) Fluoride Exhibiting Strong Second-Harmonic Generation Effect.

Perovskite structure compounds are significant candidates for designing new optical function materials due to their structural variability. Here, an inorganic tetravalent cerium fluoride, Na 2 CeF 6 , is derived from the perovskite structure through double-site cation co-substitution. Na 2 CeF 6 crystalizes in the non-centrosymmetric space group P 6 ¯ 2 m ${P}^{\bar{6}}2m$ . Edge-sharing connected NaF 9 and CeF 9 polyhedra build the whole 3D structure of Na 2 CeF 6 . Importantly, it represents the first Ce(IV) fluoride nonlinear optical (NLO) crystal and can produce a strong and phase-matchable second-harmonic generation (SHG) effect of ≈2.1 times that of KH 2 PO 4 (KDP), making it the strongest among non-lone pair electron metal fluoride system. Further, it exhibits a high laser-induced damage threshold (LIDT) of 74.65-76.25 MW cm -2 , which is over 20 times that of AgGaS 2 . It also exhibits a wide transparent region (0.5-14.3 µm). This work provides a facile route for exploring high-performance halide NLO materials.