posted on 2024-01-24, 01:05authored byXianghao Kong, Jinmiao Jiao, Yuheng She, Ning Ye, Zhanggui Hu, Yicheng Wu, Conggang Li
Borate materials are of significant interest due to their
versatile
structural configuration and competitive ultraviolet (UV) transparency
range. In this study, we present a novel rare-earth borate crystal,
KNa2Lu(BO3)2, synthesized for the
first time through a facile spontaneous crystallization method. It
adopts the centrosymmetric space group Pnma (no.
62) and yields a unique three-dimensional (3D) structural network
formed by isolated [BO3] plane triangles and distorted
[LuO7] polyhedra. This compound displays excellent thermal
stability up to ∼990 °C, demonstrating a favorable congruent
melting nature. Moreover, KNa2Lu(BO3)2 achieves a notably short UV absorption cutoff at approximately 204
nm, yielding a large band gap of 5.58 eV. Remarkably, it showcases
an enlarged birefringence of 0.044 at 1064 nm, implying its potential
as a birefringent material. Moreover, density functional theory calculations
demonstrate that the optical characteristics are predominantly influenced
by fundamental building blocks [BO3] triangles and distorted
[LuO7] polyhedra. Our findings demonstrate the potential
of KNa2Lu(BO3)2 in the development
of a birefringent candidate and enrich the structural chemistry of
rare-earth-based borates.