Determination of Crystal-Field Splitting Induced by Thermal Oxidation of Titanium

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2021-01, Vol.125 (1), p.50-56
• Main Authors: Wojtaszek, Klaudia, Błachucki, Wojciech, Tyrała, Krzysztof, Nowakowski, Michał, Zaja C, Marcin, Stȩpień, Joanna, Jagodziński, Paweł, Banaś, Dariusz, Stańczyk, Wiktoria, Czapla-Masztafiak, Joanna, Kwiatek, Wojciech M, Szlachetko, Jakub, Wach, Anna
• Format: Article
• Language: English
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/acs.jpca.0c07955

The electronic structure of transition-metal oxides is a key component responsible for material's optical and chemical properties. Specifically for metal-oxide structures, the crystal-field interaction determines the shape, strength, and occupancy of electronic orbitals. Consequently, the crystal-field splitting and resulting unoccupied state populations can be foreseen as modeling factors of the photochemical activity. Herein, we study the formation of crystal-field effects during thermal oxidation of titanium in an ambient atmosphere and range of temperatures. The X-ray absorption spectroscopy is employed for quantitative analysis of average t -e crystal-field splitting (Δoct) and relative t /e bands occupancy. The obtained result shows that Δoct changes as a function of temperature from 1.97 eV for a passive oxide layer created on a Ti metal surface at room temperature to 2.41 eV at 600 °C when the material changes into the TiO rutile phase. On the basis of XAS data analysis, we show that the Δoct values determined from L and L absorption edges are equal, indicating that the 2p and 2p core holes screen the t and e electronic states in a similar manner.