Ba₅Zn₄(BO₃)₆: A Nonlinear-Optical Material with Reinforced Interlayer Connections and Large Second-Harmonic-Generation Response

A nonlinear-optical crystal Ba₅Zn₄(BO₃)₆ (BZBO) is obtained that is constructed with [Zn₄(BO₃)₄O₆]_∞ units bridged by planar BO₃ groups along the a axis based on the flexibility of the BO₃ and ZnO₄ groups. The distance between adjacent [Zn₄(BO₃)₄O₆]_∞ layers in BZBO is 5.07 Å, which is much shorter than those of KBe₂BO₃F₂, Ba₂Zn­(BO₃)₂, and Na₂CsBe₆B5O₁₅. The smaller interlayer spacing and stronger bond between neighboring layers of BZBO contribute to a better growth habit than those of the other three. Also, with the cooperation of two kinds of nonlinear-optical active groups, BO₃ and ZnO₄, BZBO exhibits a large second-harmonic-generation response of about 2.6 times that of KDP.