A series of novel rare-earth bismuth tungstate compounds LnBiW2O9 (Ln = Ce, Sm, Eu, Er): Synthesis, crystal structure, optical and electronic properties

Abstract

The structural, optical, and electronic properties of four rare-earth bismuth tungstate compounds, LnBiW₂O₉ (Ln = Ce, Sm, Eu, Er), have been investigated by means of single-crystal X-ray diffraction, elemental analyses, and spectral measurements. For some of the compounds, the calculations of energy band structures and density of states have also been made by the density functional theory. The structure of CeBiW₂O₉ features a three-dimensional (BiW₂O₉)³⁻ anionic framework with interesting channels where Ce atoms are located. The framework is constructed by one-dimensional BiO₉ polyhedra chains and one-dimensional zigzag W₂O₉ chains via edge- and face-sharing. LnBiW₂O₉ (Ln = Sm, Eu, Er) are isostructural and their structures feature a three-dimensional network based on alternating (BiO₂)⁻ layers and (Ln₂W₂O₁₂)⁶⁻ layers connected by corner-linked chains of WO₆ octahedra. Results of spectral measurements indicate that EuBiW₂O₉ exhibit the characteristic yellow–red light emission under excitation at 395 nm, and it will be a red phosphor in designing white light-emitting diode device. The calculated results of band structures by using the density functional theory (DFT) show that the solid-state compound CeBiW₂O₉ and SmBiW₂O₉ are indirect band gap materials.