Improvement in white light emission of Dy³⁺ doped CaMoO₄ via Zn²⁺ co-doping

Abstract

The research in developing a single ingredient phosphor for white-light emission is progressively increasing. It is well known that the 4F9/2→ 6H13/2 (yellow) and 4F9/2→ 6H15/2 (blue) transitions of Dy3+ ions give near-white light emission. The white light emission of the Dy3+ ions can be enhanced by improving the crystallinity of the host phosphor via co-doping of transition metal ions. In this paper, we report a significant improvement in the white light emission of Dy3+ doped CaMoO4 by co-doping Zn2+ ions. The X ray diffraction pattern confirms the tetragonal phase of pure and doped CaMoO- 4 phosphor. The peak broadening and a red-shift in the absorption peak are observed by UV-Vis absorption analysis of Zn2+/Dy3+ doped CaMoO4. From Photoluminescence studies, we have observed that in Dy3+ doped CaMoO4, the 4% Dy3+ doped CaMoO4exhibits maximum emission. The Zn2+ ions are co-doped to further increase the luminescence intensity of CaMoO4:4%Dy3+ and the maximum luminescence is obtained for 0.25% Zn2+ concentration. Two prominent emission peaks centered at 484 nm and 574 nm related to transitionsT⃗he 4F9/2→ 6H13/2 4F9/2 6H15/2 and 4F9/2→ 6H13/2 of Dy3+ ion are observed for Dy3+ doped phosphor.transition is the forced electric dipole transition which is affected by its chemicalenvironment. After Zn2+ co-doping, the 4F9/2→ 6H13/2 transition is affected due to a change in asymmetricity around the Dy3+ ions. The 0.25% co-doping of Zn2+ gives 34% enhancement in luminescence emission of 4% Dy3+ doped CaMoO4. As a result, the CIE coordinates and color purity of the 0.25% Zn2+ co-doped CaMoO4:4Dy3+ show improvement in the overall white light emission. We have shown that with Zn2+ co-doping, the non-radiative relaxations are reduced which results in improved white light emission of Dy3+ions.

Dy3+-Assisted Negative-Thermal Quenching in Ho3+-Doped SrMoO4 for Luminescence Thermometry and Lighting Applications

“…The Dy 3d peaks confirm the +3 oxidation state of the Dy dopant. 30 The XPS spectra in Figure 3e have a binding energy peak at ∼162.38 eV, attributed to the Ho 4d 5/2 core level, validating the presence of Ho in the +3 oxidation state in the D4H2 sample. 33 3.5.…”

“…This verifies the +2 oxidation state of strontium in D4H2 and H2. 30,32 In Figure 3c, the peaks at ∼235.01 and ∼231.82 eV correspond to Mo 3d 3/2 and Mo 3d 5/2 , respectively. The peaks assigned to Mo 3d in Figure 3c verify the +6 oxidation state of Mo in D4H2 and H2.…”

“…The peaks assigned to Mo 3d in Figure 3c verify the +6 oxidation state of Mo in D4H2 and H2. 30,32 The binding energy values at ∼1334.20 and ∼1296.05 eV, depicted in Figure 3d, correspond to Dy 3d 3/2 and Dy 3d 5/2 levels, respectively. The Dy 3d peaks confirm the +3 oxidation state of the Dy dopant.…”

“…15,37 Figure 4b shows 38 The O 2− → Dy 3+ CTB lies at the longer wavelength side. 30 As the concentration of the Dy 3+ ions increases, the O 2− → Dy 3+ transition also increases, and therefore, the excitation spectra are red-shifted. The broadband peak is red-shifted as the concentration of Dy 3+ increases.…”

“…The F 2 (ν 4 ) bending mode arises due to O−Mo−O clusters of the MoO 4 2− tetrahedral. 15,28,30 The 515−910 cm −1 region has an intense absorption band centered at 785 cm −1 corresponding to Mo−O antisymmetric stretching vibration in the MoO 4 2− tetrahedral clusters. 28,30 The FTIR analysis confirms the tetragonal structure for our samples and verifies the XRD plot.…”