K<sub>3</sub>Y<sub>3</sub>(BO<sub>3</sub>)<sub>4</sub>: A Potential UV Nonlinear-Optical\nCrystal Designed by a Chemical\nSubstitution Strategy

Nonlinear-optical (NLO) crystals capable of controlling\nand manipulating\nlight to generate coherent radiation at challenging wavelengths are\nof significant interest. However, designing a new UV NLO crystal remains\ndifficult due to the rigid requirements for structure and properties.\nHerein, we have successfully designed and synthesized a novel noncentrosymmetric\n(NCS) rare-earth borate UV NLO crystal, K<sub>3</sub>Y<sub>3</sub>(BO<sub>3</sub>)<sub>4</sub>, through the heterovalence substitution\nof YAl<sub>3</sub>(BO<sub>3</sub>)<sub>4</sub>. K<sub>3</sub>Y<sub>3</sub>(BO<sub>3</sub>)<sub>4</sub> (KYBO) crystallizes in the NCS\nand polar space group of <i>P</i>6<sub>3</sub><i>mc</i>, with the structure formed by the interconnectioned BO<sub>3</sub> triangles and YO<sub>8</sub> polyhedra through corner-sharing and\nedge-sharing. The property measurements indicate that KYBO is second-harmonic-generation-active\nwith a moderate response, ∼2 × KDP. Meanwhile, KYBO can\nexhibit a short UV cutoff edge (λ<sub>cutoff</sub> < 190\nnm), indicating its potential as a new UV or deep-UV NLO crystal.