Photoluminescence of Eu-doped CaZrO red-emitting phosphors synthesized via microwave-assisted hydrothermal method

Abstract Eu-doped (1, 3 and 5 %) CaZrO red-emitting phosphors were synthesized for the first time using the microwave-assisted hydrothermal method followed by heat treatment at 1,200 °C. After the crystallization, the orthorhombic CaZrO and the non-stoichiometric cubic CaZrO phases were identified for all samples, and the portion of the non-stoichiometric phase increases as the Eu concentration increases. The excitation spectra of the phosphors display Eu f-f excitation bands (namely at 395 nm and 464 nm) and the Eu→O charge transfer band at 250 nm, confirming that the CaZrO host acts as sensitizer for the Eu luminescence. Likewise, the emission spectra feature the typical Eu emission within the red spectral region, displaying CIE color coordinates of (0.642; 0.332), (0.663; 0.330) and (0.668; 0.327) for the 1, 3 and 5 % doped samples, respectively, indicating high emission color purity. By using Eu as spectroscopic probe, the high-resolution selective emission spectra (14 K) confirm that Eu replaces Ca and Zr local sites in both CaZrO and the CaZrO phases. Finally, the high absolute emission quantum yield of the 3 %-doped phosphor found at 393 nm (0.29 ± 0.03) confirms its potential application as red-emitting phosphor, especially in rapid identification of latent fingerprints, security ink or as red-emitting coating of near-UV LEDs for WLED applications.