Improvement in white light emission of Dy³⁺doped CaMoO₄via Zn²⁺co-doping

The research in developing a single ingredient phosphor for white-light emission is progressively increasing. It is well known that the⁴F_9/2 → ⁶H_13/2(yellow) and⁴F_9/2 → ⁶H_15/2(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 CaMoO₄by co-doping Zn²⁺ions. The x-ray diffraction pattern confirms the tetragonal phase of pure and doped CaMoO₄phosphor. 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 intense emission peaks centered at 484 nm and 574 nm related to transitions⁴F_9/2 → ⁶H_15/2and⁴F_9/2 → ⁶H_13/2of Dy³⁺ion are observed for Dy³⁺doped phosphor. The⁴F_9/2 → ⁶H_13/2transition is the forced electric dipole transition which is affected by its chemical environment. After Zn²⁺co-doping, the⁴F_9/2 → ⁶H_13/2transition 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.