Effects of Dopant Addition on Lattice and Luminescence Intensity Parameters of Eu(III)-Doped Lanthanum Orthovanadate

• Published in: Journal of physical chemistry. C 2016-12, Vol.120 (50), p.28497-28508
• Main Authors: Shyichuk, Andrii, Moura, Renaldo T, Neto, Albano N. Carneiro, Runowski, Marcin, Zarad, Mohammad S, Szczeszak, Agata, Lis, Stefan, Malta, Oscar L
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.6b10778

A series of La1–x Eu x VO4 samples with a different Eu3+ content was synthesized via a hydrothermal route. An increase in the dopant content resulted in a decrease in lattice constants of the materials. Plane-wave DFT calculations with PBE functional in CASTEP confirmed this trend. Next, CASTEP calculations were used to obtain force constants of Eu–O bond stretching, using a novel approach which involved displacement of the Eu3+ ion. The force constants were then used to calculate charge donation factors g for each ligand atom. The chemical bond parameters and the geometries from DFT calculations were used to obtain theoretical Judd–Ofelt intensity parameters Ωλ. The effects of geometry changes caused by the dopant addition were analyzed in terms of Ωλ. The effects of distortions in interatomic angles of the Eu3+ coordination geometry on the Ωλ were analyzed. Effects of distortions of atomic positions in the crystal lattice on the Ωλ and photoluminescence intensities of Eu3+ 4f–4f transitions were discussed. It was shown that the ideal database geometry of LaVO4 corresponds to the highly symmetric coordination geometry of Eu3+ and very low Ω2. On the contrary, experimental intensities of the 5D0 → 7F2 transition and the corresponding Ω2 parameters were high. Consequently, distortions of crystal structure that reduce the symmetry play an important role in the luminescence of the LaVO4:Eu3+ materials and probably other Eu3+-doped phosphors based on zircon-type rare earth orthovanadates.