Na+ and Pr3+ co-doped orange-emitting CaYAl3O7 phosphors: synthesis, luminescence properties and theoretical calculations
A series of Na+ and Pr3+ co-doped orange-emitting CaYAl3O7 (CYAO) phosphors were prepared by a conventional high-temperature solid-state reaction method. The crystalline structure, the luminescence properties and the decay times of the as-prepared samples were systematically investigated by X-ray diffraction (XRD) and steady-state and time-resolved photoluminescence. Under ultraviolet (UV) light and blue light excitation, the CYAO:Pr3+ phosphors exhibited orange photoluminescence emission and show potential for application in warm white LEDs, and the emission spectra of the as-prepared samples in the near-infrared (NIR) region were detected. Furthermore, Na+ ions were designed as charge compensators to maintain the charge balance. The luminescence intensities in the visible and NIR regions can be effectively enhanced by adjusting the doping amounts of Pr3+ ions and Na+ ions. Moreover, the optical spectra of Pr3+ in the CYAO host crystals were calculated by conventional parametric modeling based on the diagonalization of the complete 91 × 91 energy matrix. The calculated optical spectra were in good agreement with the observed ones and the obtained crystal field parameters were also in a reasonable range. This systemic study, and all of the above, will give a deep insight into the luminescence mechanism of the phosphors and then open one way to exploit the new phosphors for white LEDs.