Studies on red-emitting Cr3+ doped barium aluminate phosphor obtained by combustion process

Red-emitting BaAl2O4:Cr3+ phosphor material is prepared by urea combustion route in 5 min. Powder X-ray (XRD) diffraction, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and BET surface area measurements are used to characterize the as-prepared combustion products. Electron Paramagnetic Resonance (EPR) studies have been carried out on Cr3+ ions in BaAl2O4 phosphors at room temperature and at 110 K. The number of spins participating in resonance (N) and its paramagnetic susceptibilities (χ) have also been evaluated. The excitation spectra shows two broad and intense bands corresponding to Cr3+ ion in octahedral symmetry. The red emission peak observed at 705 nm is identified as due to 2Eg → 4A2g transition from Cr3+ ions. The crystal field parameter Dq and Racah inter-electronic repulsion parameters B and C have been evaluated. From the results and analyses of the EPR and optical studies, the site symmetry of Cr3+ ion in this phosphor is attributed to a distorted octahedron.