Combustion synthesis approach for spectral tuning of Eu doped CaAl2O4 phosphors

• Published in: Journal of alloys and compounds Vol. 589; pp. 596 - 603
• Main Authors: Hari Krishna, R., Nagabhushana, B.M., Nagabhushana, H., Chakradhar, R.P.S., Suriyamurthy, N., Sivaramakrishna, R., Shivakumara, C., Rao, J.L., Thomas, Tiju
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.03.2014; Elsevier
• Subjects: CIE; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron paramagnetic resonance; Electron paramagnetic resonance and relaxation; Exact sciences and technology; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Nanocrystals and nanoparticles; Nanophosphor; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Photoluminescence; Physics; Solution combustion; Nanophosphor; Solution combustion; Electron paramagnetic resonance; CIE; Photoluminescence; Combustion synthesis; Line widths; Fabrication property relation; Nanoparticles; Europium additions; Phosphors; Chromaticity; Calcium aluminate
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.11.221

•We present a facile solution combustion method for engineering the oxidation state of Eu in open-air.•Eu2+ is stabilized in CaAl2O4 without using any reducing atmospheres viz. H2/N2 or CO.•We tune the redox state of Eu (Eu3+→Eu2+) just by changing the F/O chosen.•Influence of fuel content on luminescence and colorimetric characteristics were explored.•We have discussed the underlying mechanisms for the observed spectral characteristics. Despite being a particularly good emitter, use of divalent Eu has been seriously limited. This is because severe reducing environments or special hosts are needed during synthesis of divalent Eu containing phosphors. In this work we stabilize Eu in its 2+state (in CaAl2O4) using an open-air solution combustion reaction. The impact of fuel (F) to oxidizer (O) molar ratios (F/O=0.5–2.0) on luminescence properties is explored. Chromaticity of Eu:CaAl2O4 depends sensitively on the F/O ratio. In general, higher F/O inhibits Eu3+ and promotes Eu2+ formation, which in turn improves the quality of the blue phosphor. EPR spectra show inhomogeneous broadening effects with the increase in F/O ratio, which suggests that disorder creation is promoted when F/O is increase. This is also confirmed by an increase in emission line width in PL spectra, when F/O is increased.