Low temperature photoluminescence of Cs2NaY1−xErxCl6 excited by synchrotron radiation

Photoluminescent spectra have been recorded for Cs2NaY1−xErxCl6 at room temperature (RT) and 10 K using synchrotron radiation. Striking differences are observed between RT and 10 K emission spectra. First, unusual quenching of emission from a higher energy level (4G11/2) at RT leads to dominant visible emission at 10 K from a lower one (4S3/2). Second, emission from 2G9/2 is not observed at RT but appears at 10 K. Third, the red emission from 4F9/2 is much weaker at 10 K. Cross-relaxation quenches emission from multiplets 4D5/2 and 4F5/2 in Cs2NaErCl6 whereas emission from the former is clearly observed in dilute Cs2NaYCl6:Er3+. Detailed assignments are provided and the cross-relaxation processes are described.