Li<sub>13</sub>YGe<sub>4</sub>O<sub>16</sub>: A Mid-infrared Rare-Earth Germanate Nonlinear Optical Crystal Featuring a Broad Transmission Range and an Enlarged Band Gap
Jinmiao Jiao, Conggang Li, Yuheng She, Haiyan Shi, Wenhao Di, Ning Ye, Zhanggui Hu, Yicheng Wu
Abstract
Germanate is garnering increasing attention in the field of optoelectronics owing to its competitive optical transparency and robust stability. Herein, a novel lithium-rich rare-earth germanate, Li 13 YGe 4 O 16, was fabricated for the first time using a high-temperature solution approach. This compound adopts the asymmetric space group Cmc 2 1 (no. 36), characterized by isolated [YO 6 ] and [GeO 4 ] structural motifs with Li + cations located in the channel. Notably, Li 13 YGe 4 O 16 presents a short ultraviolet cutoff edge at 240 nm, indicative of an enlarged band gap of 4.96 eV and showcases a wide mid-infrared transmission region exceeding 6.0 μm. Moreover, Li 13 YGe 4 O 16 features exceptional thermal stability and moderate second harmonic generation (SHG) intensity. Additionally, a theoretical analysis suggests that the distorted [YO 6 ] octahedra. [GeO 4 ] and [LiO 4 ] tetrahedra play a significant role in the optical activities of Li 13 YGe 4 O 16 . These attributes endow Li 13 YGe 4 O 16 with the potential to serve as a new mid-IR nonlinear optical (NLO) crystal and enrich the structural chemistry of germanates.