The Electronic Structure of Lanthanide Impurities in TiO₂, ZnO, SnO₂, and Related Compounds

Abstract

The vacuum referred binding energy of electrons in the 4f n levels for all divalent and trivalent lanthanide impurity states in TiO 2 , ZnO, SnO 2 , and related compounds MTiO 3 and MSnO 3 (M = Ca 2+ , Sr 2+ , Ba 2+ ) and Ca 2 SnO 4 are presented. They are obtained by collecting data from the literature on the spectroscopy of lanthanide ions, and by combining that data with the chemical shift model. The model provides the energy at the top of the valence band and at the bottom of the conduction band, and it will be shown that those energies are in excellent agreement with what is known from techniques like photo-electron spectroscopy and electrochemical studies. Electronic level diagrams are presented that explain and predict aspects like absence or presence of lanthanide 4f-4f or 5d-4f emissions and the preferred lanthanide valence. © 2013 The Electrochemical Society. [DOI: 10.1149/2.005403jss] All rights reserved.Manuscript received October 17, 2013. Published December 20, 2013 Recently the chemical shift model was introduced 1 for the lanthanide impurities in compounds. By using spectroscopic data for different lanthanides like Ce 3+ , Pr 3+ , Tb 3+ , Eu 3+ , Yb 3+ in the same compound, the model enables to derive the electronic structure with the absolute electron binding energies, i.e., relative to the energy of the electron at rest in vacuum, in all divalent and all trivalent lanthanides.2 It has been applied to about 50 different compounds (fluorides, chlorides, aluminates, phosphates, borates etc.) and full consistency with available experimental data from different fields of science was demonstrated.2-4 It was found that in inorganic compounds based on rare earth cations, like YPO 4 and LaBO 3 , and/or alkaline and/or alkaline earth cations like CaF 2 and CaGa 2 S 4 , the binding energy at the bottom of the conduction band E C is typically near −2 eV. Sc-based compounds like ScBO 3 and ScPO 4 tend to show lower values for E C which was attributed to a large binding energy of electrons in the 3d-shell of Sc 3+ /Sc 2+ that forms the bottom of the conduction band. 4 In this work the model will be applied to TiO 2 , ZnO, SnO 2 , and related ternary compounds. The compounds were selected because of their high importance for many applications.TiO 2 has been and still is thoroughly investigated for its photocatalytic activity and ability for photoelectrochemical water splitting. 5The activity can be enhanced or modified by doping with transition metal or rare earth ions. 6,7 Much is already known on the electronic structure and properties of this compound in its various crystallographic appearances, i.e., rutile-TiO 2 , anatase-TiO 2 , and brookiteTiO 2 . Here we will focus on the anatase-phase. ZnO is an important member of the II-VI semiconductor family. An extensive review on the physical and optical properties of ZnO can be found in Ref. 8. At ambient conditions only the wurtzite phase is thermodynamic stable and all data and schemes in this work will pertain to that phase. SnO 2 has much in common with Zn...

Trap Energy Upconversion‐Like Near‐Infrared to Near‐Infrared Light Rejuvenateable Persistent Luminescence

“…These three excitation bands at 300, 500, and 700 nm should be assigned to the electronic transitions of Bi 2+ 2 P 1/2 – 2 P 3/2 (1), 2 P 1/2 – 2 P 3/2 (2), and 2 P 1/2 – 2 S 1/2 , [ 23 ] while this emission band can be assigned to the 2 P 3/2 (1) → 2 P 1/2 transition of the tetrahedral coordinated divalent bismuth, IV Bi 2+ , as CaSnO 3 comprises a stiff 3D network of the Ca tetrahedral anion groups, and IV Bi 2+ will precipitate onto a Ca‐site (Detail Discussion in Figures S6–S8 in the Supporting Information). [ 18b,24 ] The low‐temperature spectra also support this optical attribution (Figure S9, Supporting Information).…”

Role of electron transfer in Ce3+ sensitized Yb3+ luminescence in borate glass

“…The U(6,A) represents the energy difference between Eu 2þ and Eu 3þ ground state, and therefore by knowing this, the VRBE diagram for entire lanthanide family can be constructed using the chemical shift model as suggested by Dorenbos. 22,28 The Eu 3þ CT energy (5.4 6 0.1 eV) is used for locating the valence band position in the VRBE scheme. Note that the only relevant parameters for predicting electron transfer possibilities in the VRBE scheme of Fig.…”

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