A new stable polymorph of Li2TeMo3O12 with wide mid-infrared transparency and a large Raman response

• Published in: Inorganic chemistry frontiers Vol. 10; no. 12; pp. 3595 - 3604
• Main Authors: She, Yuheng, Liang, Fei, Jiao, Jinmiao, Zhao, Wenli, Ye, Ning, Hu, Zhanggui, Wu, Yicheng, Li, Conggang
• Format: Journal Article
• Language: English
• Published: London Royal Society of Chemistry 13.06.2023
• Subjects: Atmospheric windows; Crystallization; Diffraction patterns; Inorganic chemistry; Optical properties; Phase transitions; Polymorphism; Raman lasers; Single crystals; Thermal analysis; Thermal stability
• ISSN: 2052-1545; 2052-1553
• DOI: 10.1039/d3qi00572k

Polymorphism is crucial for unraveling crystallization mechanisms, predicting crystal structures and discovering novel materials. A new high-symmetry polymorph of Li2TeMo3O12, β-Li2TeMo3O12, was identified successfully by a spontaneous crystallization technique, and it exhibits improved thermal stability and crystallizes in the trigonal space group R3 (No. 148) in contrast to the metastable α-Li2TeMo3O12. Thermal analysis and variable-temperature X-ray diffraction powder patterns demonstrated an irreversible phase transition of Li2TeMo3O12 from α-Li2TeMo3O12 to β-Li2TeMo3O12. High-quality and centimetre-sized single crystals of β-Li2TeMo3O12 were extracted via a facile flux approach. Moreover, optical characterization showed that it has a large bandgap of 3.05 eV accompanied by high transparency from 0.34 to 5.4 μm, encompassing a 3–5 μm atmospheric window. Remarkably, the title compound features the intriguing merits of an intrinsically strong Raman shift located at 955 cm−1 and a narrow line width of 12.54 cm−1, which enable it to act as a stimulated Raman laser, making it a promising mid-infrared Raman crystal. Additionally, theoretical investigations are used to evaluate the fundamental relationships between the compound's structure and optical properties.