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

Abstract

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 Å. 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.