NaKZn(BO) and β-KZnBO: Two Zincoborates with Deep-UV Cutoff Edge.

The design of new materials is important for the exploration of compounds with good properties. Borates have attracted extensive attention because of their excellent properties and rich structures. Herein, two new zincoborates NaKZn(BO) and β-KZnBO with fundamental building blocks (FBBs) as the isolated [BO] group were synthesized. The polymerization degree of B-O units is regulated by cations and [ZnO] polyhedra, and the structural arrangement is further affected, to improve the properties. The transmittance spectra show that NaKZn(BO) and β-KZnBO have deep ultraviolet (UV) cutoff edge (183 nm, 181 nm), and theoretical calculations indicate their birefringence is 0.012 and 0.029 at 1064 nm, respectively. Indicating that NaKZn(BO) has the potential to be used as a deep-UV waveplate material. More importantly, we analyzed the reason why the birefringence of β-KZnBO is twice that of NaKZn(BO) from the perspective of structure. These results are important for the design of optical materials.