Luminescence in undoped CaYAl3O7 produced via the Pechini method

Abstract

The luminescent properties of CaYAl3O7 (CYAM) were carried out in undoped powder samples produced via Pechini method. The thermal analysis combined with XRD measurements showed that 1000°C/4h is the best condition for the CYAM synthesis. Morphological analysis showed submicrometric particles with irregular shape. Photoluminescence (PL) emission and excitation spectra were studied with excitation in the ultraviolet and vacuum ultraviolet spectral region using synchrotron radiation. The CYAM band gap energy was measured and found to be around 6.8eV. Low intense emission band around 4.4eV, upon excitation at 6.5eV, was assigned to the self-trapped excitons (STE) that are generated during the VUV excitation. Three main emission bands peaking at 2.57, 2.94 and 3.23eV are responsible for most of the PL emission and radioluminescence (RL) emission in CYAM. Time-resolved measurements under pulsed 4.7eV light showed that the PL decay curve is composed by 3 main processes with very short lifetime, smaller than 30ns, and a small amount of long time constant process. Time-resolved RL measurements exciting with 4056eV photons, above the Ca K edge, showed that the decay curve is composed by two processes with time constants around 27 and 130ns and a small component due to a long decay constant bigger. All this features allowed the identification of the main emissions centres at 2.94 and 3.23eV to the F+ centres, while the emission centre at 2.57eV is due to the F type centre.