An electron paramagnetic resonance and optical study of Cr doped BaAl12O19 powders

The BaAl12O19 powders doped with Cr3+ ions have been prepared by a low-temperature combustion synthesis method. As prepared combustion synthesized powder was characterized using powder X-ray diffraction and energy dispersive analysis of X-ray methods. The diffuse reflectance spectrum exhibits three bands characteristic of Cr3+ ions in distorted octahedral symmetry. The EPR spectra exhibit signals with the effective g values at g=1.96, 2.27 and 4.85. The signals with the effective g values at g=2.27 and 4.85 have been attributed to the isolated Cr3+ ions. The signal at g=1.96 has been attributed to the exchange coupled Cr3+ ions. The excitation spectrum exhibits bands characteristic of Cr3+ ions in distorted octahedral symmetry. The ligand field parameter Dq and the Racah interelectronic repulsion parameters B and C have been evaluated from the excitation spectrum. The emission spectrum exhibits an intense band centered at 700 nm (14,286 cm−1) and this band has been attributed to 2Eg→4A2g transition.