Effect of Cr³⁺ doping on structural and optical properties of Eu³⁺ doped LaVO₄ phosphor

In this work, the Eu³⁺, Cr³⁺ doped and co-doped LaVO₄ 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 Cr³⁺ ion. The photoluminescence excitation spectra of Eu³⁺, Cr³⁺ co-doped LaVO₄ phosphor exhibit bands due to Eu³⁺ and Cr³⁺ ions. The Eu³⁺ doped LaVO₄ phosphor exciting at 393 and 316 nm wavelengths gives intense red color at 614 nm due to the ⁵D₀ → ⁷F₂ transition of the Eu³⁺ ion. When the Cr³⁺ ion is co-doped in the Eu³⁺ doped LaVO₄ phosphor the emission spectra contain emission bands due to Eu³⁺ and Cr³⁺ ions. The emission intensity of Eu³⁺ doped phosphor reduces due to energy transfer from Eu³⁺ to Cr³⁺ ions in presence of Cr³⁺ ions upon 393 and 386 nm excitations. The lifetime of the ⁵D₀ level of Eu³⁺ ions decreases in the Eu³⁺, Cr³⁺ co-doped LaVO₄ phosphor, which also reflects the energy transfer. The Eu³⁺, Cr³⁺ co-doped LaVO₄ phosphor also produces a large amount of heat upon 980 nm excitation. Thus, the Eu³⁺, Cr³⁺ co-doped LaVO₄ phosphors may be used for LEDs, solid state lighting and heat generating devices.