Effect of Cr 3+ doping on structural and optical properties of Eu 3+ doped LaVO 4 phosphor.

In this work, the Eu 3+ , Cr 3+ doped and co-doped LaVO 4 phosphors have been prepared through a high temperature solid-state reaction method. The powder XRD patterns of phosphors are very sharp and intense, which reflects a highly crystalline nature of phosphors. The XRD data were also refined by a Rietveld refinement method. The particle size of the phosphor samples lies in the sub-micron to micron range. The existence of La, Eu, Cr, V and O elements was verified by EDS spectra. The FTIR spectra show various absorption bands due to different vibrating groups. The optical band gap of the phosphor decreases on increasing concentration of Cr 3+ ion. The photoluminescence excitation spectra of Eu 3+ , Cr 3+ co-doped LaVO 4 phosphor exhibit bands due to Eu 3+ and Cr 3+ ions. The Eu 3+ doped LaVO 4 phosphor exciting at 393 and 316 nm wavelengths gives intense red color at 614 nm due to the 5 D 0 → 7 F 2 transition of the Eu 3+ ion. When the Cr 3+ ion is co-doped in the Eu 3+ doped LaVO 4 phosphor the emission spectra contain emission bands due to Eu 3+ and Cr 3+ ions. The emission intensity of Eu 3+ doped phosphor reduces due to energy transfer from Eu 3+ to Cr 3+ ions in presence of Cr 3+ ions upon 393 and 386 nm excitations. The lifetime of the 5 D 0 level of Eu 3+ ions decreases in the Eu 3+ , Cr 3+ co-doped LaVO 4 phosphor, which also reflects the energy transfer. The Eu 3+ , Cr 3+ co-doped LaVO 4 phosphor also produces a large amount of heat upon 980 nm excitation. Thus, the Eu 3+ , Cr 3+ co-doped LaVO 4 phosphors may be used for LEDs, solid state lighting and heat generating devices.