Browsing by Author "Prashant Kumar Pandey"

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Emission color tuning and dual-mode luminescence thermometry design in Dy3+/Eu3+ co-doped SrMoO4 phosphors
(Institute of Physics, 2024) Vaibhav Chauhan; Prashant Dixit; Prashant Kumar Pandey; Satyam Chaturvedi; Praveen C Pandey
The challenge of building a highly reliable contactless temperature probe with high sensitivity, good temperature-induced color discriminability, and economical synthesis has prompted the research community to work in the field of rare-earth-based luminescence thermometry. Moreover, the fast-growing market for optoelectronic devices has increased the demand for tunable color-emitting phosphors. In this study, Dy3+/Eu3+ co-doped SrMoO4 phosphors were developed as tunable color-emitting source and dual-mode luminescence thermometer. A facile and cost-effective auto-combustion method was used to synthesize the phosphors. Our work demonstrates a viable scheme for tailoring the emission of single-phase phosphors by precisely controlling the dopant concentrations and by modulating excitation wavelength. The overall emission is tuned from greenish-yellow to white and greenish-yellow to reddish-orange. A detailed energy transfer process from the host to the Ln3+ ions and between the Ln3+ ions is discussed. Further, anti-thermal quenching in the emission of Dy3+ ion is observed when excited with 297 nm. The dual-mode luminescence thermometry has been studied by analyzing the fluorescence intensity ratio of Dy3+ and Eu3+ ions upon excitation at 297 nm. The maximum relative sensitivity value for 4% Eu3+ co-doped SrMoO4:4%Dy3+ phosphor is 1.46% K−1 at 300 K. Furthermore, the configurational coordinate diagram is presented to elucidate the nature of temperature-dependent emission. Therefore, our research opens up new avenues for the development of color-tunable luminescent materials for various optoelectronic and temperature-sensing applications. © 2023 IOP Publishing Ltd
Improvement in white light emission of Dy3+ doped CaMoO4 via Zn2+ co-doping
(Institute of Physics, 2022) Prashant Dixit; Prashant Kumar Pandey; Vaibhav Chauhan; Pratik Deshmukh; S. Satapathy; Praveen C Pandey
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 Dy3+ ions can be enhanced via 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 CaMoO4 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 CaMoO4 exhibits 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 intense emission peaks centered at 484 nm and 574 nm related to transitions 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 of Dy3+ ion are observed for Dy3+ doped phosphor. The 4F9/2 → 6H13/2 transition is the forced electric dipole transition which is affected by its chemical environment. 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 of chromaticity diagram and the 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. © 2022 IOP Publishing Ltd.