Due to various assemble types of the trigonal BO₃ or tetrahedral BO₄ units, the structural multiformity of borates makes it attractive for researchers to explore new functional materials.

Borates containing planar BO₃ units with p-orbitals have unsymmetrical electron density which may lead to large microscopic second-order susceptibility (b⁽²⁾) and optical anisotropy (Δn).

A research group led by Prof. PAN Shilie at Xinjiang Technical Institute of Physics & Chemistry (XTIPC) of Chinese Academy of Sciences synthesized a new lithium zinc borate Li₆Zn₃(BO₃)₄ and characterized it structurally for the first time. The study was published in Inorganic Chemistry Frontiers as a cover story.

Li₆Zn₃(BO₃)₄ crystallizes in the triclinic space group of P-1, and the BO₃ triangles in Li₆Zn₃(BO₃)₄ are approximately parallel to each other, which generates a relatively large birefringence (0.065 at 1064nm).

Researchers reported that face-sharing LiO₄ tetrahedra for the first time. The structure comparisons were carried out among all the available lithium-containing borates together with title compounds to analyze the particularity of face-sharing LiO₄ tetrahedra.

They found that the shorter Li-Li distances in face-sharing LiO₄ tetrahedra configuration will increase the repulsive force and decrease the stability of the structure, making the face-sharing LiO₄ tetrahedra rarely found in the borates.

Besides, Li₆Zn₃(BO₃)₄ was found to have two reversible phase changes, which implies that Li₆Zn₃(BO₃)₄ is a potential candidate for phase change material.

This work was supported by the National Natural Science Foundation of China, National Basic Research Program of China, the National Key Research Project, etc.