Tunable and white photoluminescence from Tb3+-Eu3+ activated Ca0.3Sr0.7Al2O4 phosphors and analysis of chemical states by X-ray photoelectron spectroscopy

Tb3+ and Eu3+ activated Ca0.3Sr0.7Al2O4 phosphors with tunable emissions were synthesized via urea assisted combustion method. The phosphors were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy and photoluminescence (PL) spectroscopy. The XRD pattern of the Ca0.3Sr0.7Al2O4:Tb3+, Eu3+ powder showed was composed of a single phase associated with monoclinic SrAl2O4, suggesting that SrAl2O4 was the main structure in the Ca0.3Sr0.7Al2O4 mixed aluminate host and Ca2+ substituted the Sr2+ ions. Consistent with the three dimensional structure of SrAl2O4, the XPS data indicated that there were two different lattice sites occupied by Sr2+ in the lattice and resultantly Ca2+ could also be found at two different lattice sites. Tunable and white PL was generated when the phosphors were optically excited at different wavelengths using a monochromatized xenon lamp. The white PL with the Commission International de L'Eclairage (CIE) coordinates (x = 0.343, y = 0.325) was a result of the combination of the red line emission from Eu3+ and the blue and green line emissions from Tb3+.