Na2CeF6: 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, Na₂CeF₆, is derived from the perovskite structure through double-site cation co-substitution. Na₂CeF₆ crystalizes in the non-centrosymmetric space group P 6 ¯ 2 m ${P}^{\bar{6}}2m$ . Edge-sharing connected NaF₉ and CeF₉ polyhedra build the whole 3D structure of Na₂CeF₆. 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 KH₂PO₄ (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 AgGaS₂. 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.