Ca9Na1/3M2(1-x)/3(PO4)7:2x/3Eu3+ (M = Gd, Y): A promising red-emitting phosphor without concentration quenching for optical display applications

Zero-quenching red-emitting phosphors Ca9Na1/3M2(1-x)/3(PO4)7:2x/3Eu3+ (M = Gd, Y) were successfully synthesized by solid-state method. The analysis of XRD, SEM, UV-vis DRS, luminescent spectra, and the emission dynamics curves were applied to investigate the obtained powders. These results showed that Eu3+-activated Ca9Na1/3M2(1-x)/3(PO4)7 (M = Gd, Y) phosphors can absorb the wavelength from 220 to 480 nm, which is matched well with commercial near-UV chips, and emit intense red light without concentration quenching. Notably, the integral intensities calculated from Ca9Na1/3Gd2(1-x)/3(PO4)7:2x/3 Eu3+ and Ca9Na1/3Y2(1-x)/3(PO4)7:2x/3Eu3+ phosphors were about 3.05 and 2.64 times higher than that of commercial phosphor Y2O3:Eu3+, respectively. In addition, the CIE color coordinate was calculated to be (0.65, 0.34). It should be pointed out that the FWHM of 5D0→7F2 transition band was greatly expanded due to the presence of multi-sites for Eu3+ ions in the hosts. These results suggest that the obtained phosphors have the potential for lighting and optical display applications.