Photoluminescence properties and energy transfer of ZnNb2O6: Eu3+, Sm3+ orange-red phosphors for WLEDs

Abstract

Eu3+, Sm3+ co-doped ZnNb2O6 orange-red phosphors were synthesized through the solid-state reaction method for the first time. The microstructure, photoluminescence properties, decay time, energy transfer mechanism, thermal stability and CIE chromaticity coordinates of Zn1-x-yNb2O6: xSm3+, yEu3+ phosphors were studied systematically. The XRD patterns and refinement results demonstrate that the rare earth ions have been effectively doped into ZnNb2O6 host lattices. Under the excited of 406 nm, the main emission peak intensity of Sm3+ decreased and Eu3+ increased with increasing of Eu3+ ion concentration in the Zn0.99-yNb2O6: 0.01Sm3+, yEu3+ phosphors, which due to the energy transfer from Sm3+ to Eu3+. Through the decay time measurements, energy transfer mechanism was proved to the electric dipole-electric dipole effect in the resonance transfer mode, and the transfer efficiency of ZnNb2O6: 0.25Eu3+, 0.01Sm3+ phosphor is calculated as 85.39%. Through the analysis of thermal stability properties of the co-doped sample, the thermal activation energy of thermal quenching is calculated to be 0.235 eV. The CIE chromaticity coordinates for co-doped sample are located at the orange-red region, the correlated color temperature and color purity are calculated to be 1927 K and 95.87%, respectively. In addition, a WLED device can be obtained by combing the co-doped sample with commercial blue (BaMgAl10O17: Eu2+) and green ((Sr, Ba)2SiO4: Eu2+) phosphors on a 395 nm N-UV LED chip. These results indicate that ZnNb2O6: Eu3+, Sm3+ phosphor is a promising candidate for WLEDs.