Experimental and Theoretical Study of the Electronic Structures of Lanthanide Indium Perovskites LnInO3
Journal Article
·
· Journal of Physical Chemistry. C
- Univ. of Oxford (United Kingdom). Dept. of Chemistry. Inorganic Chemistry Lab.; OSTI
- Univ. of Oxford (United Kingdom). Dept. of Chemistry. Inorganic Chemistry Lab.
- Univ. of Oxford (United Kingdom). Dept. of Chemistry. Inorganic Chemistry Lab.; Xiamen Univ. (China). College of Chemistry and Chemical Engineering. State Key Lab. of Physical Chemistry of Solid Surfaces
- Univ. of Oxford (United Kingdom). Dept. of Chemistry. Inorganic Chemistry Lab.; Technische Universität Darmstadt (Germany). Inst. of Materials Science/ Surface Science Division
- Univ. of Warwick, Coventry (United Kingdom); Binghamton Univ., NY (United States). Dept. of Applied Physics & Astronomy
- Cardiff Univ., Cardiff (United Kingdom). School of Chemistry. Cardiff Catalysis Inst.
- Univ. College London (United Kingdom). Dept. of Chemistry; Univ. College London (United Kingdom). Thomas Young Centre; Science and Technology Facilities Council (STFC), Oxford (United Kingdom). Diamond Light Source, Ltd.
- Norwegian Univ. of Science and Technology (NTNU), Trondheim (Norway). Dept. of Materials Science and Engineering
- Univ. College London (United Kingdom). Dept. of Chemistry. Inorganic Chemistry Lab.; Univ. College London (United Kingdom). Dept. of Chemistry
Ternary lanthanide indium oxides LnInO3 (Ln = La, Pr, Nd, Sm) were synthesized by high-temperature solid-state reaction and characterized by Xray powder diffraction. Rietveld refinement of the powder patterns showed the LnInO3 materials to be orthorhombic perovskites belonging to the space group Pnma, based on almost-regular InO6 octahedra and highly distorted LnO12 polyhedra. Experimental structural data were compared with results from density functional theory (DFT) calculations employing a hybrid Hamiltonian. Valence region X-ray photoelectron and K-shell X-ray emission and absorption spectra of the LnInO3 compounds were simulated with the aid of the DFT calculations. Photoionization of lanthanide 4f orbitals gives rise to a complex final-state multiplet structure in the valence region for the 4fn compounds PrInO3, NdInO3, and SmInO3, and the overall photoemission spectral profiles were shown to be a superposition of final-state 4fn-1 terms onto the cross-section weighted partial densities of states from the other orbitals. The occupied 4f states are stabilized in moving across the series Pr-Nd-Sm. Band gaps were measured using diffuse reflectance spectroscopy. These results demonstrated that the band gap of LaInO3 is 4.32 eV, in agreement with DFT calculations. This is significantly larger than a band gap of 2.2 eV first proposed in 1967 and based on the idea that In 4d states lie above the top of the O 2p valence band. However, both DFT and X-ray spectroscopy show that In 4d is a shallow core level located well below the bottom of the valence band. Band gaps greater than 4 eV were observed for NdInO3 and SmInO3, but a lower gap of 3.6 eV for PrInO3 was shown to arise from the occupied Pr 4f states lying above the main O 2p valence band.
- Sponsoring Organization:
- EPSRC; USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division
- Grant/Contract Number:
- AC02-05CH11231
- OSTI ID:
- 1816449
- Journal Information:
- Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 11 Vol. 125; ISSN 1932-7447
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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