Oxygen K-edge spectra of Yb2O 3 polymorphs, Yb2SiO5, and Yb2Si2O7: First-principles simulations and EELS measurements

Abstract

First-principles calculations, along with a core-hole technique, are adopted to simulate oxygen K-edge spectra for three polymorphs of Yb2O3 and two types of ytterbium silicates (i.e., Yb2SiO5 and Yb2Si2O7). The twe Yb silicates are compared with experimental spectra, which are measured via electron energy-loss spectroscopy for a polycrystalline sample including both phases. The simulated O K-edge spectra of cubic, monoclinic, and hexagonal Yb2O3 exhibit characteristic twin peaks, which resulted from crystal fi eld splitting of unoccupied Yb5 d orbitals in Yb-O polyhedra. Spacing between the two peaks refl ects a degree of distortion of the polyhedra and local coordination environments around O atoms. The simulated and experimental O K-edge spectra of Yb2SiO5 and Yb2Si2O7 also show twin peaks, where lower-energy peaks are signifi cantly reduced compared to those of Yb2O3. A small diff erence in the lower-energy peaks, which refl ect the local environments of O atoms, enables us to identify Yb silicate phases from an O K-edge spectrum. The derived insights could be widely extended to rare-earth oxides.