A novel green-emitting SrCaSiAl sub(2)O sub(7):Eu super(2+) phosphor for white LEDs

The crystal structure of a Eu super(2+)-activated SrCaSiAl sub(2)O sub(7) phosphor was refined and determined as a tetragonal structure with the refinement converged to R sub(p) = 7.05%, R sub(wp) = 10.67%, and chi super(2) = 2.637 by Rietveld refinement using a synchrotron light source. By doping different contents of Eu super(2+), the emission peaks gives a range between 526 nm and 535 nm. The estimated Stokes shifts and Commission International de l'Eclairage (CIE) chromaticity coordinates are 16576-16896 cm super(-1) and (0.3155, 0.5073) to (0.3685, 0.5284), respectively. By tuning the ratio of phosphors and silicone, the optical properties of the three-band white LEDs could be tuned, changing the CIE chromaticity coordinates from yellow (0.4343, 0.4857) to white-light (0.3311, 0.3460), the correlated color temperature (CCT) between 3599 K and 5558 K, and color rendering index (Ra) in the range 83.1 to 79.1, under a forward bias current of 350 mA.