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Abstract Owing to its unique electronic configuration Xe4 f 0 , Ce 4+ ‐compound is a highly desired in the field of advanced nonlinear optical materials, yet its synthesis remains a great challange. Herein, we report a series of cerium fluorides, including a pure Ce 4+ ‐fluoride, high‐performance Na 2 (Ce 4+ )F 6 ; three mixed valance state samples, (Mix1–3, with increasing Ce 3+ concentration); and a fully reduced pure Ce 3+ ‐fluoride Na 1.5 (Ce 3+ ) 1.5 F 6 . In particular, Na 2 (Ce 4+ )F 6 , shows an SHG response (4×KDP), and a wide band gap (4.77 eV), which are the strongest and widest among all Ce‐containing materials to date. With systematic studies, we demonstrate that the subtle Ce 3+ impurity significantly reduces performance. By being aware of this fact and consciously controlling experimental conditions, we can ensure the synthesis of pure Na 2 (Ce 4+ )F 6 , which exhibits excellent overall performance and shows great potential for future applications. This work not only reinforced the crucial role of Ce 4+ in significantly enhancing the key performance, but also provided invaluable experimental evidence and theoretical support for the future design of more efficient and superior functional materials.
Li et al. (Tue,) studied this question.