Crystal-Like Atomic Arrangement and Optical Properties of 25La 2 O 3 -75MoO 3 Binary Glasses Composed of Isolated MoO 4 2 .

Transparent and brown La2 O3 -MoO3 binary glasses were prepared in bulk form using a levitation technique. The glass-forming range was limited, with the primary composition being approximately 25 mol % La2 O3 . The 25La2 O3 -75MoO3 glass exhibited a clear crystallization at 546 °C, while determining its glass transition temperature was difficult. Notably, despite its amorphous nature, the glass possessed a density and packing density comparable to those of crystalline La2 Mo3 O12 . X-ray absorption fine structure and Raman scattering analyses revealed that the glass structure closely resembles La2 Mo3 O12 due to the presence of isolated MoO4 2- units, whereas disordered atomic arrangement around La atoms was confirmed. The glass demonstrated transparency ranging from 378 to 5500 nm, and the refractive index at 1.0 μm was estimated to be 2.0. The optical bandgap energy was 3.46 eV, which was slightly smaller than that of La2 Mo3 O12 . Additionally, the glass displayed a transparent region ranging from 6.5 to 8.0 μm. This occurrence results from the decreased diversity of MoO n units and connectivity of Mo-O-Mo, which resulted in the reduced overlap of multiphonon absorption. This glass formation, with its departure from conventional glass-forming rules, resulted in distinctive glasses with crystal-like atomic arrangements.