Full-color tuning by controlling the substitution of cations in europium doped Sr8-xLa2+x(PO4)6-x(SiO4) xO2 phosphors

Abstract A full-color tunable phosphor by co-substituting Sr 2+ and P 5+ for La 3+ and Si 4+ in the single phased oxy-apatite Sr 8-x La 2+x (PO 4 ) 6-x (SiO 4 ) x O 2: Eu 2+ (SLPSiO; x = 0, 2, 4, 6) phosphor were prepared via solid state reaction method from powder based precursors. The crystal structure information of cell parameters and average bond lengths from luminescence centers to its ligands was analyzed using Rietveld refinement. All the crystal structure of series of phosphors include two different sites of Eu 2+ , the 7-coordinated Sr1 sites and the 9-coordinated Sr2 sites. The different behaviors of luminescence evolution were due to the Eu 2+ ions prefer higher energy sites in the Sr 8 La 2 (PO 4 ) 6 O 2 (for x = 0) host, but lower energy sites in the Sr 2 La 8 (SiO 4 ) 6 O 2 host (for x = 6). Also, the red PL originating from the trivalent europium ions appeared due to the increase in the La 3+ /Sr 2+ ratio with increasing x. The blue point (0.2016, 0.1144), bluish white (5000–8300 K CCT), and yellowish white point (2600–3700 K CCT) in the CIE coordination through red colors are included in the ‘Fabricated LED’ curve, which are suitable for the application of these blends in white-light near UV LEDs. Moreover, the internal quantum efficiency of the x = 0 phosphor approached up to 90%.