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KMeY(PO4)2:5% Eu3+ phosphates have been synthesized by a novel hydrothermal method. Spectroscopic, structural, and morphological properties of the obtained samples were investigated by X-ray, TEM, Raman, infrared, absorption, and luminescence studies. The microscopic analysis of the obtained samples showed that the mean diameter of synthesized crystals was about 15 nm. The KCaY(PO4)2 and KSrY(PO4)2 compounds were isostructural and they crystallized in a rhabdophane-type hexagonal structure with the unit-cell parameters a = b ≈ 6.90 Å, c ≈ 6.34 Å, and a = b ≈ 7.00 Å, c ≈ 6.42 Å for the Ca and Sr compound, respectively. Spectroscopic investigations showed intense 5D0 → 7F4 transitions connected with D2 site symmetry of Eu3+ ions. Furthermore, for the sample annealed at 500 °C, europium ions were located in two optical sites, on the surface of grains and in the bulk. Thermal treatment of powders at high temperature provided better grain crystallinity and only one position of dopant in the crystalline structure. The most intense emission was possessed by the KSrY(PO4)2:5% Eu3+ sample calcinated at 500 °C. [ABSTRACT FROM AUTHOR]

The hydroxyapatite nanopowders of the Eu3+-doped, Cu2+-doped, and Eu3+/Cu2+-co-doped Ca10(PO4)6(OH)2 were prepared by a microwave-assisted hydrothermal method. The structural and morphological properties of the products were investigated by X-ray powder diffraction (XRD), transmission electron microscopy techniques (TEM), and infrared spectroscopy (FT-IR). The average crystal size and the unit cell parameters were calculated by a Rietveld refinement tool. The absorption, emission excitation, emission, and luminescence decay time were recorded and studied in detail. The 5D0 → 7F2 transition is the most intense transition. The Eu3+ ions occupied two independent crystallographic sites in these materials exhibited in emission spectra: one Ca(1) site with C3 symmetry and one Ca(2) sites with Cs symmetry. The Eu3+ emission is strongly quenched by Cu2+ ions, and the luminescence decay time is much shorter in the case of Eu3+/Cu2+ co-doped materials than in Eu3+-doped materials. The luminescence quenching mechanism as well as the schematic energy level diagram showing the Eu3+ emission quenching mechanism using Cu2+ ions are proposed. The electron paramagnetic resonance (EPR) technique revealed the existence of at least two different coordination environments for copper(II) ion. [ABSTRACT FROM AUTHOR]

This paper discusses the origin of emission quenching in yttrium orthovanadate codoped with Eu 3+ and Sb 3+ ions. Highly crystalline yttrium orthovanadate nanoparticles with chemical composition Y 1- x - y Eu x Sb y VO 4 ( x = 0-5.4 mol %, y = 0-2.1 mol %) were prepared using the modified Pechini's method. The particles' structural and morphological properties were studied using X-ray powder diffraction and scanning electron microscopy techniques. Moreover, X-ray photoelectron spectroscopy was used to determine the oxidation state and surface bonding of individual ions in the obtained materials. The photoluminescence spectral and dynamical properties were investigated in detail. The observed Eu 3+ luminescence depreciation is ascribed to reabsorption mediated by a low-lying Sb 3+ -to-V 5+ metal-to-metal charge transfer state in conjunction with lattice defects absorbing in the visible spectral region.

In this study, solid-state solutions of yttrium orthovanadate-phosphate with varying concentrations of codopants (Eu 3+ , Bi 3+ ) have been obtained via coprecipitation. An ionic radii mismatch between V 5+ and P 5+ substituents is manifested in broad XRD lines. The sharpening of the XRD lines is observed with increasing bismuth ions concentration in the Eu 3+ codoped YV 0.5 P 0.5 O 4 matrix. The difference in the number of the Stark components for the 5 D 0 → 7 F J transitions indicates changes in the lattice and a number of possible Eu 3+ sites. A thorough, systematic spectroscopic analysis of YV 0.5 P 0.5 O 4 : x mol % Eu 3+ , y mol % Bi 3+ was conducted at room temperature and 5 K. Metal-to-metal energy transfers occurring between Eu 3+ , V 5+ , and Bi 3+ optically active ions have been investigated. Additionally, efficiency of the Bi 3+ -Eu 3+ energy transfer (ET) was calculated.

In the present work, a precipitation method was employed to prepare nanosized YAsO 4 doped with Eu 3+ ions. The raw nanomaterials have been thermally treated in a temperature range between 500 and 900 °C for 3 h. The XRD analysis demonstrated that the powders were single-phase nanopowders with high crystallite dispersion. Our studies were focused on relating the luminescence properties of the Eu 3+ dopant to the nanocrystallite (NC) size. The average NC size varied accordingly between 15 and 45 nm. We have found that the size effect is manifested mainly in the expansion of the cell volume and broadening of XRD peaks, as indicated by Rietveld analysis. Moreover, the emission and excitation spectra, although typical for Eu 3+ ions, demonstrated some degree of variability with calcination temperatures and doping concentration. To explain these differences, a detailed analysis of luminescence spectra by the Judd-Ofelt theory has been performed.