Abstract
While highly efficient red-emitting inorganic phosphors have been discovered in the substance class of alkaline earth oxo(nitrido)lithoaluminates, new narrow-band green- and yellow-emitting components are being sought to improve the performance of phosphor-converted light-emitting diodes (pc-LEDs). Various solid-state reactions were carried out under protective gas atmosphere in nickel crucibles and sealed tantalum ampules to synthesize Sr[Li(3)AlO(4)], Sr[Li(3)GaO(4)], and five substitutional derivates of Sr[Li(3)(Al(1-x) Ga (x) )O(4)] at moderate temperatures. The observation of a linear increase in the unit cell parameters as a function of the increasing gallium mole fraction x in Sr[Li(3)(Al(1-x) Ga (x) )O(4)] revealed Vegard behavior in the solid-solution series, which was derived from powder X-ray diffraction data. The isomorphic crystallization of the new oxolithogallate Sr[Li(3)GaO(4)] and the known oxolithoaluminate Sr[Li(3)AlO(4)] in an ordered variant of the U[Cr(4)C(4)] aristotype was verified on the basis of powder and single-crystal X-ray diffraction data. Photoluminescence spectroscopy was used to investigate the narrow-band emissions in the substitution series of Eu(2+)-activated Sr[Li(3)(Al(1-x) Ga (x) )O(4)] under blue-light excitation. The emission maximum was shifted to higher energies as the gallium mole fraction increased. Peak wavelengths were observed at λ(em) = 572 nm (fwhm equals 47 nm, 1446 cm(-1), 0.18 eV) for yellow-emitting Sr[Li(3)AlO(4)]:Eu(2+) and at λ(em) = 554 nm (fwhm equals 49 nm, 1589 cm(-1), 0.20 eV) for green-emitting Sr[Li(3)GaO(4)]:Eu(2+). Sr[Li(3)AlO(4)]:Eu(2+) has excellent thermal quenching resistance with a photoluminescence emission intensity of >93% at T = 423 K relative to the room temperature value, making this inorganic phosphor a potential candidate for solid-state lighting applications.