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

Abstract

A series of La 1−x Eu x VO 4 samples with a different Eu 3+ 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 Eu 3+ 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 Ω λ . The effects of geometry changes caused by the dopant addition were analyzed in terms of Ω λ . The effects of distortions in interatomic angles of the Eu 3+ coordination geometry on the Ω λ were analyzed. Effects of distortions of atomic positions in the crystal lattice on the Ω λ and photoluminescence intensities of Eu 3+ 4f−4f transitions were discussed. It was shown that the ideal database geometry of LaVO 4 corresponds to the highly symmetric coordination geometry of Eu 3+ and very low Ω 2 . On the contrary, experimental intensities of the 5 D 0 → 7 F 2 transition and the corresponding Ω 2 parameters were high. Consequently, distortions of crystal structure that reduce the symmetry play an important role in the luminescence of the LaVO 4 :Eu 3+ materials and probably other Eu 3+ -doped phosphors based on zircon-type rare earth orthovanadates.

Red‐Emitting Magnetic Nanocomposites Assembled from Ag‐Decorated Fe3O4@SiO2 and Y2O3:Eu3+: Impact of Iron‐Oxide/Silver Nanoparticles on Eu3+ Emission

“…On the basis of recent theoretical considerations, the Ω 2 intensity parameter is by far mostly influenced by small angular changes in the local coordination geometry,,, while Ω 4 and mainly Ω 6 are by far the most sensitive to lanthanide‐ligating atom bond distances and, therefore, to covalency . This fact together with changes in the ligating atoms polarizabilities (α) have been used to rationalize the hypersensitive character of certain 4 f intraconfigurational transitions to changes in the chemical environment.…”

Optical Vacuum Sensor Based on Lanthanide Upconversion—Luminescence Thermometry as a Tool for Ultralow Pressure Sensing

“…A great number of optically active functional materials is based on the Ln 2+/3+ , because of their unique spectroscopic properties, such as multicolor photoluminescence induced by UV or near‐infrared (NIR) (energy up‐conversion) irradiation, narrow absorption/emission bands, large spectral shift of the emission bands in relation to the absorption ones, long emission lifetimes, etc . Matrices hosting Ln 3+ ions are usually fluorides, oxides, vanadates, phosphates, and borates .…”

Synthesis and Investigation of La,Ca ‐Doped EuVO4 Nanoparticles with Enhanced Excitation by Near Violet Light

“…The 320 nm band in vanadate compounds is usually connected with 1 A 1 → 1 T 2 transitions in the VO 4 3‐ anions . The additional wide excitation band near 370–390 nm is related with influence of the Ca 2+ impurities as this band was not observed nor for the EuVO 4 neither for the Ca‐free La 1− x Eu x VO 4 samples (Figure , curve 5,). Origin of this band will be considered below when discussing emission spectra in their comparison with properties of the La 1− x − y Eu y Ca x VO 4 compounds.…”

“…Previous investigations have shown that partial replacements of the RE cations with iso‐ and heterovalent ions in the REVO 4 compounds lead to various changes of their physical and chemical characteristics . In particular, replacement of the RE cations with alkaline earth (AE) cations (Ca 2+ , Sr 2+ , Ba 2+ ) in the RE vanadate nanoparticles causes increase of luminescent intensity and arising of additional excitation band in violet spectral range of light …”