UV emissions in Gd~(3+) doped or Gd~(3+)-Pr~(3+) Co-doped Ⅲ-Ⅲ perovskite-type RMO_3 (R = Y, La; M = Al, Ga)

摘要

The effects of Gd~(3+)-Pr~(3+) co-doping on the Gd~(3+) UV emission properties were investigated using Gd~(3+) doped and Gd~(3+)-Pr~(3+) co-doped Ⅲ-Ⅲ perovskite-type oxides (YAlO_3, LaAlO_3, and LaGaO_3). All the samples had a narrow UV emission at 314 nm. Pr~(3+) co-doping in the YAlO_3 host enhanced the UV emission from Gd~(3+), but the other hosts, LaAlO_3 and LaGaO_3, did not. In Gd~(3+)-Pr~(3+) co-doped YAlO_3, the Pr 5d state, which appeared in the band gap and did not overlap the conduction band, provided an intense absorption due to the Pr~(3+) 4f-5d transition, which enhanced the Gd~(3+) emission intensity by transferring the excitation energy absorbed by the Pr~(3+) ions to Gd~(3+). On the other hand, in Gd~(3+)-Pr~(3+) co-doped LaAlO_3 and LaGaO_3, the Pr 5d state partly or completely overlapped the conduction band. Although the excitation energy was absorbed by Pr~(3+), the energy was transferred to the host lattice through the conduction band. These results suggest that the energy location of the Pr 5d state relative to the conduction band substantially influences the energy transfer from Pr~(3+) to Gd~(3+).