Optical and structural properties of chromium impurities in niobium–gallium oxide

• Cr3+ doped niobium–gallium oxides were prepared by solid state reaction and wet chemical method.
• We show bands in red region.
• Spectra are associated to Cr3+ ions in octahedral sites.

In this work, the optical properties of the gallium–niobium oxide doped with chromium ions were investigated. The samples were obtained by wet chemical and solid-state methods, investigated by X-ray powder diffraction and the data were refined by Rietveld methods. The morphology was determined by scanning electron microscope (SEM) images. The photoluminescence, excitation and photoacoustic measurements showed broad and intense bands in the red region of the spectrum, associated with energy transitions of chromium ions in octahedral sites. From the optical spectra and using the crystal field theory, the energy parameters were obtained.