Abstract
A series of Eu3+ doped CaSiO3/SiO2 nano-phosphor powder of controlled grain size, crystalline structure, and chemical composition were synthesized using the microemulsion technique. The morphology, size, and shape of the synthesized nanophosphorous powder were investigated using transmission electron microscopy and X-ray diffraction (XRD) analysis. XRD profiles of samples sintered over 600 °C, suggested phase shift from amorphous powder grain to more ordered polycrystalline powder of triclinic type wollastonite, CaSiO3, with preferred crystal phase orientation of (112) and tetragonal type cristobalites of SiO2. The grain size, crystallinity, and chemical composition of the host matrix, activator and sensitizer strongly affected both the absorption and emission bands of these samples. The amplitude of both the orange and red emission bands significantly increased with sintering temperature. The emission band is red-shifted with decreasing grain sizes. These bands displayed good sensitivity to ionic concentration of the Si4+, Ca2+, and Eu3+. With increasing Ca2+ ion concentration both the intensity of the red photoluminescence (PL) band increased and a concentration quenching observed. Increase in Si4+ ion concentration led to quenching in PL intensity of both the orange and red bands, whereas the amplitude of the blue-band slightly increased. With increasing Eu3+ ion concentration the red-band initially increased whereas it started decreasing at higher sample concentration. In the presence of Ca2+ ion as a sensitizer, the sample showed a remarkable PL property-including–about 100% photon conversion efficiency and a two-fold increase in excitation and emission photons.
Highlights
Eu3+ doped phosphors are employed in lighting and display technologies such as electroluminescence cells, plasma display panels, high-efficiency fluorescent lamps, light emitting diodes, and waveguides as they show remarkable photoluminescence (PL) properties [1,2,3,4,5]
A phosphor that absorbs photons in this domain is suitable for making display panels, fluorescent lamps, and sensors [6,7]
The peak positions and intensities of these bands bear a strong relationship with the size distribution of the crystal grain, their chemical composition, and morphology
Summary
Eu3+ doped phosphors are employed in lighting and display technologies such as electroluminescence cells, plasma display panels, high-efficiency fluorescent lamps, light emitting diodes, and waveguides as they show remarkable photoluminescence (PL) properties [1,2,3,4,5]. In pure form, Eu3+ ions show emission lines extending from visible to near infra-red domain of the electromagnetic spectrum. These ions usually absorb photons in the ultraviolet (UV) region (200 to 270 nm) and emit orange and red lines in the visible region. A phosphor that absorbs photons in this domain is suitable for making display panels, fluorescent lamps, and sensors [6,7]. Earlier reports have shown that crystal grain size, their distribution, resistance to particle agglomeration, and spherical morphology are the most critical factors for a phosphor to have good luminescent characteristics [8,9,10]
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