Local Environments Around Eu³⁺ and Eu²⁺ Ions in Dual Light‐Emitting BaSnO₃:Eu Nanomaterials

Abstract

The change in the environment around Eu3+ and Eu2+ species as a function of their concentration in BaSnO3:Eu nanomaterials has been investigated by low‐temperature (77 K) luminescence and electron paramagnetic resonance (EPR) spectroscopy. These materials show dual emission from the europium ions upon single‐wavelength excitation. Europium ions (Eu3+ and Eu2+) occupy the centrosymmetric Ba2+ sites up to 4 atom‐% in BaSnO3, beyond which it forms a separate europium oxide phase with both Eu2+ and Eu3+ ions. There is energy transfer from the BaSnO3 host to the Eu2+ ions in the samples. Upon single‐wavelength UV excitation (280 nm) of the BaSnO3:Eu nanomaterials, strong emissions at 430, 480, 590 and 612 nm, characteristic of exciton recombination in the host BaSnO3 (430 nm), the 4f65d1(T2g)→4f 7(8S7/2) transition of Eu2+ (480 nm) and intra‐4f transitions of Eu3+ (590 and 612 nm) have been observed. For samples that contain more than 4 atom‐% europium ions based on steady‐state luminescence measurements and lifetime values that correspond to the 5D0 level of Eu3+ ions, it is inferred that there are mainly three types of Eu3+ ions: the first at Ba2+ sites with perfect dodecahedral geometry in the bulk of the nanomaterials, the second at Ba2+ sites at the surface of the nanomaterials and the third type as a separate europium oxide phase. Similarly, EPR specroscopy confirms the presence of three types of environments for the Eu2+ species.

Fluorinated Eu‐Doped SnO2 Nanostructures with Simultaneous Phase and Shape Control and Improved Photoluminescence

“…[10h] XPS spectra of F 1s core electrons (Figure C) display only one peak located at ≈684.8 eV, which is a typical value for the fluorinated SnO 2 system such as SnOF 2 or the surface Sn‐F, as well as EuF 3 or EuOF and the surface Eu‐F bonds. [6b], However, broad and weak peaks present in the Eu 3d XPS spectra (Figure D), even for the nominally 20 mol% doped sample, indicate a low Eu content in the surface region. In the XPS spectra of the Eu 3d 5/2 core‐level region, the Eu 3d 5/2 line splits into two peaks (≈1135 and ≈1125 eV), which is consistent with the trivalent europium oxide (Eu 2 O 3 ) .…”

“…The overall composition analysis from energy dispersive spectroscopy (EDS), which we note can only be considered as a rough estimate, shows that the O and Sn contents decrease with increasing Eu 3+ levels, while both F and Eu content greatly increase. The non‐stoichiometric ratio of O/Sn and F/Eu points out on several possible doping pathways: i) surface oxygen is substituted by F, leading to formation of e.g., SnOF 2 ; ii) formation of Eu x F y compounds takes place; and iii) Sn 4+ is substituted by Eu 3+ with oxygen vacancies produced, which is compensated by F − ions to maintain the charge balance.…”

Influence of Zirconium (Zr4+) Substitution on the Crystal Structure and Optical and Dielectric Properties of Sr0.8Mg0.2(Sn1–xZrx)O3 Ceramics

“…It is acknowledged that the PL emissions are significant for the order/disorder ratio in a sample . In semiconductors, the PL characteristics depend upon the surface morphology and calcination temperature of the raw materials. , As a consequence, the production of medium-energy levels and the enabling of various energetic transitions between them led to the formation of the wide emission spectra that were seen in the samples …”

Unusual blue and red luminescence properties of BaO–ZrO2 nanocrystals

“…The introduction of barium (with a larger ionic radius) into the ZrO 2 lattice would enhance these defects. The main sources of localized defect centers in ZrO 2 crystal lattice is oxygen vacancies/interstitials and Zr vacancies/interstitials (Zr 3+ interstitials) [27][28][29][30]. These defects exist primarily on the surface of the ZrO 2 nanocrystals owing to their high-surface area at the nanoscale.…”