The development of new nonlinear optical (NLO) materials for deep‐ultraviolet (DUV) applications is in great demand. However, the synthesis of an ideal DUV NLO crystal is a serious challenge. Herein, three new alkali‐metal fluorooxoborates, AB₄O₆F (A=K, Rb, and Cs, and a mixed cation between two of them), were successfully synthesized by cation regulation. It is found that all reported compounds exhibit short UV absorption edges (<190 nm), and show second harmonic generation (SHG) responses ranging from 0.8 to 1.9 KH₂PO₄ (KDP). Interestingly, by judicious selection of the A‐site alkali‐metal cations, the arrangement of NLO‐active structural units is fine‐tuned to an optimal configuration, which contributes to large SHG responses.

中文翻译：

---

阳离子调谐的含氟硼酸盐的合成：寻求最佳的深紫外非线性光学材料

迫切需要开发用于深紫外线（DUV）应用的新型非线性光学（NLO）材料。但是，理想的DUV NLO晶体的合成是一个严峻的挑战。在这里，通过阳离子调节成功地合成了三种新的碱金属氟硼酸盐，AB ₄ O ₆ F（A = K，Rb和Cs，以及它们之间的混合阳离子）。发现所有报告的化合物均显示出短的紫外线吸收边缘（<190 nm），并显示出从0.8到1.9 KH ₂ PO ₄（KDP）的二次谐波生成（SHG）响应。有趣的是，通过明智地选择A位碱金属阳离子，可以将NLO活性结构单元的排列微调到最佳配置，这有助于获得较大的SHG反应。