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Preparation, Electronic Structure of Gadolinium Oxyhydride and Low-energy 5d Excitation Band for Green Luminescence of Doped Tb3+ Ions

Abstract

Oxyhydride compounds of GdHO and GdHO:Tb3+ were successfully prepared by solid state reaction of GdH3, Gd2O3 and Gd2O3:Tb3+ under H2 atmosphere. From the XRD analysis, GdHO belongs to cubic fluorite structure (space group Fm3 @#x0305;m, lattice parameter a = 5.38450(4) Å for GdHO and 5.38523(6) Å for GdHO:Tb), which is different from the tetragonal fluorite-like superstructure for previously reported LnHO (Ln= La, Ce, Pr and Nd) (space group P4/nmm). The prepared GdHO:Tb3+ shows photoluminescence bands in the range between 470 and 650 nm, which are attributed to Tb3+:5D47FJ transitions. In the photoluminescence excitation spectrum, the broad 4f-5d bands of Tb3+ was clearly observed at around 320 nm, which is one of the lowest 5d energy position compared with other Tb3+-doped compounds. This shift can be caused by the partially coordinated hydride ions with strong covalency around Tb3+, which give a large nephelauxetic effect and crystal field splitting. The lifetime of Tb3+:5D4 is almost the same from 83 to 500 K and drops above 500 K. The thermal luminescence quenching of the 5D47FJ is caused by thermally activated crossover through the 5d energy level to the ground state.The band gap energy of GdHO (5.39 eV) was smaller than that of cubic- and monoclinic- Gd2O3 (5.93 and 6.10 eV, respectively). Based on the constructed vacuum referred binding energy diagram and DFT calculation, the top of valence band (VB) energy of GdHO is much higher than that of cubic- and monoclinic-Gd2O3 due to the higher energy level of hydride 1s orbital than that of oxide 2p orbital.

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Publication details

The article was received on 10 Apr 2018, accepted on 09 Jun 2018 and first published on 12 Jun 2018


Article type: Paper
DOI: 10.1039/C8TC01682H
Citation: J. Mater. Chem. C, 2018, Accepted Manuscript
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    Preparation, Electronic Structure of Gadolinium Oxyhydride and Low-energy 5d Excitation Band for Green Luminescence of Doped Tb3+ Ions

    J. Ueda, S. Matsuishi, T. Tokunaba and S. Tanabe, J. Mater. Chem. C, 2018, Accepted Manuscript , DOI: 10.1039/C8TC01682H

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