Influences of substituting Na+ ions in Eu2+, Mn2+ doped Ba9Y2Si6O24 phosphors

Near-ultraviolet (NUV)-excitable phosphors composed of Ba8.9-(1/2)pNapEu0.1Y2Si6O24 (p = 0-0.8) and Ba8.7-qNa0.4Eu0.1MnqY2Si6O24 (q = 0-0.4) were prepared via a solid-state reaction in a reducing atmosphere. The X-ray diffraction patterns of the obtained phosphors were examined to index the peak positions. After Na+ substitution for Ba2+ in the Ba8.9Eu0.1Y2Si6O24 host lattice, the clear shift from green to yellow emission was observed. The Gaussian components of Ba8.9-(1/2)pNapEu0.1Y2Si6O24 (p = 0, 0.4, and 0.8) phosphors were exploited by using the three different Eu2+ ion sites in the host lattice. The dependence of the luminescent intensity of the Mn2+ co-doped (q = 0-0.4) host lattices on the fixed Na+ and Eu2+ contents was also investigated. Co-doping Na+ with Mn2+ and Eu2+ emitters in the host structure enabled efficient energy transfer from Eu2+ to Mn2+. The mechanism underlying this energy transfer was also discussed. The Commission Internationale de I'Eclairage (CIE) coordinates near the yellow and red regions of the obtained phosphors were observed. Each of Ba8.9Eu0.1Y2Si6O24, Ba8.7Na0.4Eu0.1Y2Si6O24, and Ba8.6Na0.4Eu0.1Mn0.1Y2Si6O24 phosphors with a 405 nm LED chip was fabricated. The color rendering index (CRI, Ra) at correlated color temperature (CCT) with the CIE coordinates was exhibited for the LEDs. The thermal quenching and activation energy for the Ba8.7Na0.4Eu0.1Y2Si6O24 and Ba8.6Na0.4Eu0.1Mn0.1Y2Si6O24 phosphors were measured.