Colour Tuning of Single Host Phosphors for White Light by Al Addition

We report a newly found strong disturbing effect of Al addition to the intensity ratios of blue and green emissions from single host full-colour phosphor of Ba_-3MgSi_2-xAl_xO₈:0.02Eu₂₊, 0.1Mn²⁺ for near-UV excited white light. The phase-pure silicate phosphor in the size of around 4μm is prepared by salt-assisted spray pyrolysis route, having three-colour emissions at the wavelength peak values of 437nm, 500nm and 608nm simultaneously under the excitation of 375nm. The amount variation of Al ion added to the phosphor host results in a drastic change of the intensity ratio between green and blue emissions, while the intensity of red light keeps unchanged. As a consequence, the combination of three colours lies in the white light region and can be tuned by precisely controlled addition of Al content. The Raman spectroscopy verifies the modifying effect of Al ion to the tetrahedral network in silicate hosts. We assume that by addition of Al ion, the amount of those two kinds of Eu²⁺ substituting for those two kinds of Ba²⁺ lattice sites with distinct energy levels of blue and green featured emissions can be adjusted to contribute to diversification of the ratios of blue and green emissions.