Synthesis and luminescence characteristics of CaB2O4:Er3+, Li+ phosphor

A series of Er3+ doped CaB2O4 phosphors were synthesized by conventional solid state reaction method. XRD and FTIR spectra confirmed the crystal phase formation of CaB2O4:Er3+, Li+ phosphor. Structural and morphological studies were carried out using transmission electron microscopy and scanning electron microscopy. UV-vis-NIR optical absorption spectrum of CaB2O4:Er3+, Li+ phosphor was analyzed on the basis of Judd-Ofelt theory. Spontaneous emission transition probabilities and branching ratios were evaluated using Judd-Ofelt intensity parameters. Excitation spectra reveal strong transitions from the ground state 4I15/2 of Er3+ ions. Dependence of Er3+ doping concentration on the luminescence properties of the phosphor was systematically investigated under the excitation wavelengths 407 and 980 nm. Emission spectra consist of characteristic emission peaks of Er3+ at 550 nm (4S3/2→4I15/2), 663 nm (4F9/2→4I15/2) and 770 nm (4I9/2→4I15/2) in visible and 1531 nm (4I13/2→4I15/2) in NIR regions. Dependence of Er3+ ion concentration on emission intensity suggests concentration quenching in the prepared phosphor sample and also suggests the possible interaction type dipole-dipole among rare earth ions. From the luminescence decay analysis excited state life time of rare earth ion is found to be 6.92 μs. The calculated CIE color coordinates lies in the greenish yellow region. Since the prepared phosphor gives emission in green-red and NIR regions they might have potential application in LEDs and lasers.