Self-activated multicolor emissions in Ca2NaZn2(VO4)3:Eu3+ phosphors for simultaneous warm white light-emitting diodes and safety sign

Self-activated Eu3+-doped Ca2NaZn2(VO4)(3) multicolor-emitting phosphors were prepared by a facile critic-assisted sol-gel technique. Both the photoluminescence (PL) excitation and three-dimensional PL emission spectra revealed that the synthesized samples exhibited an intense absorption band in the range of 250-370 nm. The emission intensity of the phosphors was greatly dependent on the doping concentration and the optimal value was found to be 7 mol%. The concentration quenching mechanism is attributed to the dipole-dipole interaction and the critical distance is 18.8 angstrom. With the addition of Eu3+ ions, multicolor emissions were observed in the resultant phosphors when excited at 290 nm. The thermal stability of phosphors was characterized by temperature-dependent PL emission spectra. By manipulating the temperature, the emitting color of the prepared phosphors was tuned from yellowish red to orange, and ultimately to pure red. Additionally, the near-ultraviolet (NUV) chip-based light-emitting diode device, which was fabricated by coating the blended resultant phosphors, commercial blue-emitting and green-emitting phosphors on the NUV chip, emitted glaring warm white light with superior color rendering index and impressive correlated color temperature. These results suggest that the self-activated Eu3+-doped Ca2NaZn2(VO4)(3) multicolor-emitting phosphors are suitable for safety sign in high temperature circumstance and indoor lighting. (C) 2017 Elsevier Ltd. All rights reserved.