Synthesis and photoluminescence characteristics of near white light emitting CaB2O4:Dy3+, Li+ phosphor

A series of Dy3+ doped CaB2O4 phosphors were synthesized by conventional solid state reaction method. XRD analysis reveals that the crystal structure of the sample was well matched with the orthorhombic CaB2O4. FTIR spectra characterize various vibrational bonds present in the samples. SEM images indicate that the prepared phosphor have microstructure nature with irregular morphology. UV-Vis-NIR optical absorption spectrum of CaB2O4:Dy3+, Li+ phosphor was analyzed on the basis of Judd-Ofelt theory and the J-O intensity parameters (Omega(lambda)) were evaluated. The radiative properties such as transition probability (A(R)), stimulated emission cross-section (sigma(e)) etc. were calculated. Excitation spectra reveal strong transitions from the ground state H-6(15/2) of Dy3+ ions. The prepared phosphor samples provide emission in blue (F-4(9/2) -> H-6(15)/(2)), yellow (F-4(9/2 ) -> H-6(13)/(2)) and red ( F-4(9/2) -> H-6(11)/(2)) regions under an excitation wavelength of 350 nm. The alkali metal Li+ was added to maintain the charge neutrality of the phosphor system which also enhances the luminescence intensity of Dy3+ ions. CIE chromaticity studies show that the prepared phosphor samples are exhibiting near white light emission and corresponding correlated color temperature (CCT) were appearance in cool region. The results suggest that as-synthesized phosphors have potential application in the field of NUV white light emitting diodes (W-LEDs).