Effects of Codoping on Site-Dependent Eu 3+ Luminescence in Perovskite-Type Calcium Zirconate and Hafnate.

The single doping of Eu 3+ and codoping with Ga 3+ or La 3+ into perovskite (ABO 3 )-type CaZrO 3 and CaHfO 3 were carried out to investigate the effect of codoping on the photoluminescence (PL) features of Eu 3+ , attempting the site-selective Eu 3+ doping at either A or B sites. To comprehend the Eu 3+ PL features, the accurate locations of Eu 3+ were examined by X-ray absorption near edge structure (XANES) and the proportions of Eu 3+ located at A or B sites (Eu 3+ (A) or Eu 3+ (B); Eu Ca • or Eu Zr ' /Eu Hf ' ) were analyzed. No considerable differences in the XANES spectra and in the proportions of Eu 3+ (A) and Eu 3+ (B) were observed in the single-doped samples. On the other hand, the shape of the XANES spectra and the Eu 3+ proportion markedly differed in the codoped samples. Ga 3+ codoping (Ga Zr ' /Ga Hf ' ) achieved Eu 3+ (A) proportions of more than 90%, and La 3+ codoping (La Ca • ) resulted in the largest Eu 3+ (B) proportions of approximately 40%. In both PL and PL excitation spectra, the site-dependent spectral features were changed depending on the proportion of Eu 3+ (A) and Eu 3+ (B), especially the PL peaks at 595 nm were intensified most in the La 3+ codoped samples. Consequently, the site-dependent Eu 3+ PL features in CZO and CHO were found to become more conspicuous by the effect of Ga 3+ or La 3+ codoping. The results also revealed that the codoped ions work not only to compensate for the charge of aliovalent Eu 3+ but also to drive Eu 3+ to the intentional doping sites.