Ishwar Prasad Sahu

Ca₂MgSi₂O₇:Ce³⁺, Ca₂MgSi₂O₇:Eu²⁺ and Ca₂MgSi₂O₇:Eu²⁺,Ce³⁺ phosphors were prepared using the solid‐state reaction method. The crystal structures of the sintered phosphors were of melilite type, which has a tetragonal crystallography. The chemical compositions of the sintered phosphors was confirmed by energy dispersive X‐ray spectroscopy. The different thermoluminescence kinetic parameters [activation energy (E), frequency factor (s) and order of the kinetics (b)] of these phosphors were evaluated and compared using the peak shape method. Under ultraviolet excitation, the emission spectra of both Ca₂MgSi₂O₇:Eu²⁺ and Ca₂MgSi₂O₇:Eu²⁺,Ce³⁺ phosphors were composed of a broad emission band peaking at 530 nm. When the Ca₂MgSi₂O₇:Eu²⁺ phosphor is co‐doped with Ce³⁺ ions, photoluminescence, afterglow and mechanoluminescence intensity was strongly enhanced. Ca₂MgSi₂O₇:Eu²⁺ showed some afterglow with a short persist time. On incorporation of Ce³⁺, efficient energy transfer from Ce³⁺ to Eu²⁺ was found and the emission intensity of Eu²⁺ was enhanced. The mechanoluminescence intensities of Ca₂MgSi₂O₇:Ce³⁺, Ca₂MgSi₂O₇:Eu²⁺ and Ca₂MgSi₂O₇:Eu²⁺,Ce³⁺ phosphors increased proportionally increased with the increase in impact velocity, which suggests that these phosphors can be used as sensors to detect stress in an object.

In this paper, we report the dysprosium-doped strontium magnesium silicate, namely, SrMgSi₂O₆:xDy³⁺ (x = 1.0, 1.5, 2.0, 2.5, and 3.0 mol%) phosphors prepared by the traditional high temperature solid state reaction method. The prepared phosphors were characterized by X-ray diffraction, field emission scanning electron microscope coupled with the energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared technique. The crystal structures of sintered phosphors were an akermanite type which belongs to the tetragonal crystallography with space group P4̅2₁ m. The chemical composition of the sintered phosphor SrMgSi₂O₆ :Dy³⁺ (2%) was confirmed by the EDS. Under the ultraviolet excitation, the emission spectra of SrMgSi₂O₆ :xDy³⁺ (x = 1.0, 1.5, 2.0, 2.5, and 3.0 mol%) phosphors were composed of broadband with the characteristic emission of Dy³⁺ ions peaking at 475 nm (blue) and 574 nm (yellow), originating from the transitions of ⁴F_9/2 → ⁶H_j state (where j = 15/2 and 13/2). The combination of these two emissions constituted white light emission as indicated on the Commission Internationale de l'Eclairage chromaticity diagram. The possible mechanism of the prepared white light emitting SrMgSi₂O₆ :xDy³⁺ (x = 1.0, 1.5, 2.0, 2.5, and 3.0 mol%) phosphors were also investigated. Investigation on decay property show that the prepared phosphor held fast and slow decay process. In order to investigate the suitability of the samples as white color light sources for industrial uses, correlated color temperature (CCT) and color rendering index (CRI) were calculated. Values of CCT and CRI were found, well within the defined acceptable range.