Luminescence of SrAl₂O₄:Cr³⁺

Samples of SrAl₂O₄ and SrAl₂O₄:Cr³⁺ were prepared by mixing the powder materials SrCO₃, Al₂O₃, and Cr₂O₃. The crystal structures of the undoped and doped samples were analyzed by X-ray diffraction (XRD) measurements. The diffraction patterns reveal a dominant phase, characteristic of the monoclinic SrAl₂O₄ compound and another unknown secondary phase, in small amount, for doped samples. The data were fitted using the Rietveld method for structural refinements and lattice parameter constants (a, b, c, and β) were determined. Luminescence of Cr³⁺ ions in this host is investigated for the first time by excitation and emission spectroscopy at room temperature. Emission spectra present a larger band and a smaller structure associated to the \( ^{{\text{4}}} T_{{\text{2}}} {\text{ (}}^{{\text{4}}} F{\text{)}} \to ^{{\text{4}}} A_{{\text{2}}} {\text{ (}}^{{\text{4}}} F{\text{)}} \) and \( ^{{\text{2}}} E{\text{ (}}^{{\text{2}}} G{\text{)}} \to ^{{\text{4}}} A_{{\text{2}}} {\text{ (}}^{{\text{4}}} F{\text{)}} \) electronic transitions, respectively. The obtained results are analyzed by crystal-field theory and the crystal-field parameter, Dq, and Racah parameters, B and C, are determined from the excitation measurements.