Structural and photoluminescence properties of stannate based displaced pyrochlore-type red phosphors: Ca_3−xSn₃Nb₂O₁₄:xEu³⁺

Abstract

New stannate based displaced pyrochlore-type red phosphors, Ca(3-x)Sn3Nb2O14:xEu(3+), were prepared via a conventional solid state method. The influence of partial occupancy of Sn in both A and B sites of the pyrochlore-type oxides on the photoluminescence properties was studied using powder X-ray diffraction, FT-Raman, transmission electron microscopy, scanning electron microscopy with energy dispersive spectrometry, UV-visible absorption spectroscopy, and photoluminescence excitation and emission spectra with lifetime measurements. The structural analysis establishes that these oxides belong to a cubic displaced pyrochlore type structure with a space group Fd3̄m. These phosphors exhibit strong absorptions at near UV and blue wavelength regions and emit intense multiband emissions due to Eu(3+ 5)D0-(7)F(0, 1, 2) transitions. The absence of characteristic MD transition splitting points out that local cation disorder exists in this type of displaced pyrochlores, reducing the D(3d) inversion symmetry, which is not evidenced by such disorder in the X-ray diffraction analysis. The unusual forbidden intense sharp (5)D0-(7)F0 transition indicates single site occupancy of Eu(3+) with a narrower range of bonding environment, preventing the cluster formation. This is supported by the stable (5)D0 lifetime with Eu(3+) concentration. The Judd-Ofelt intensity parameter assessment corroborates these results. The CIE color coordinates of these phosphors were found to be (0.60, 0.40), which are close to the NTSC standard values (0.67, 0.33) for a potential red phosphor.

Energy Upconversion in Rare‐Earth‐Doped Tin‐Based Double Halo Perovskites, A2SnCl6 (A = K, Rb, and Cs)

“…On the other hand, the Ω 4 parameter is influenced by the electronegativity of the ligands around rare‐earth ions. [ 29 ] The Ω 4 parameter is sensitive to the separation between the metal ion and the donor ligand. The integrated emission intensities of the radiative emissions 5 D 0 → 7 F J ( J = 2, 4) are linked with the radiative emission rates as: [ 28 ] …”

“…[28] Among the three parameters, Ω 2 depends on the covalency and the site asymmetry of the rareearth ions. [29] The low the value of Ω 2 indicates either higher the centrosymmetric of the ion site or more ionic its chemical bond with the ligands or both. On the other hand, the Ω 4 parameter is influenced by the electronegativity of the ligands around rare-earth ions.…”

“…On the other hand, the Ω 4 parameter is influenced by the electronegativity of the ligands around rare-earth ions. [29] The Ω 4 parameter is sensitive to the separation between the metal ion and the donor ligand. The integrated emission intensities of the radiative emissions 5 D 0 → 7 F J (J = 2, 4) are linked with the radiative emission rates as: [28] Here, A 0-2, 4 and A 0-1 denote the radiative emission rates for 5 D 0 → 7 F 2, 4, and 5 D 0 → 7 F 1 transitions; I 0-2, 4, and I 0-1 represent the integral intensities for 5 D 0 → 7 F 2, 4, and 5 D 0 → 7 F 1 transitions with the corresponding energies of and hν 0-2, 4 and hν 0-1 , respectively.…”

Hydrothermal growth of Zn2SnO4:Eu,Ca for red emission

“…Red‐light‐emitting phosphors are of particular interest to researchers due to their application in the fabrication of energy conserving solid state white light emitting diodes (white LEDs) . Europium ions (Eu 2+ or Eu 3+ ) doped semiconductor materials are used to obtain high intensity red emission . Emission lines of Eu 3+ ion correspond to the electronic transitions from the excited state 5 D 0 → 7 F J (where, j=1,2,3…) levels of the 4f 6 configuration which is exploited to obtain red emission .…”

Influence of Structural Disorder on the Photoluminescence Properties of Eu3+ Doped Red Phosphors: Ca2Y3‐xNb3O14: xEu3+

“…In our previous study, the influence of partial substitution of small cation like Sn on both A and B sites of the pyrochlore type oxides on the photoluminescence properties was studied in detail. The photoluminescence spectra of the developed phosphors exhibit intense multiband emissions due to Eu 3+ 5 D 0 ‐ 7 F 0, 1, 2 transitions.…”