Local microstructure and photoluminescence of Er-doped 12CaO·7Al 2O 3 powder

Abstract

Er-doped 12CaO·7Al 2O 3 (C12A7:Er) powders were prepared using the sol-gel method followed by annealing inorganic precursors. X-ray diffraction (XRD), Raman and absorption spectra revealed that Er ions existed and substituted Ca 2+ lattice site in C12A7. The photoluminescence of C12A7:Er at room temperature was observed in the visible and infrared region using 488 nm (2.54 eV) Ar + line as excitation source, respectively. The sharp and intense green emission bands with multi-peaks around 520 nm and 550 nm correspond to the transitions from the excited states 2H 11/2 and 4S 3/2 to the ground state 4I 15/2, respectively. Furthermore, red emission band around 650 nm was also observed. It was attributed to the electronic transition from excited states 4F 9/2 to the ground state 4I 15/2 inside 4f-shell of Er 3+ ions. The intensive infrared emission at 1.54 μm was attributed to the transition from the first excited states of 4I 13/2 to the ground state ( 4I 15/2). The temperature dependent photoluminescence of infrared emission showed that the integrated intensity reached a maximum value at near room temperature. The forbidden transitions of intra-4f shell electrons in free Er 3+ ions were allowed in C12A7 owing to lack of the inversion symmetry in the Er 3+ position in C12A7 crystal field. Our results suggested that C12A7:Er was a candidate for applications in Er-doped laser materials, and full color display.