Isomorphism of Sr[LiAlO] and Sr[LiGaO] - Syntheses, Crystal Structure, and Europium(II) Luminescence.

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[LiAlO], Sr[LiGaO], and five substitutional derivates of Sr[Li(Al Ga )O] at moderate temperatures. The observation of a linear increase in the unit cell parameters as a function of the increasing gallium mole fraction in Sr[Li(Al Ga )O] 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[LiGaO] and the known oxolithoaluminate Sr[LiAlO] in an ordered variant of the U[CrC] 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-activated Sr[Li(Al Ga )O] under blue-light excitation. The emission maximum was shifted to higher energies as the gallium mole fraction increased. Peak wavelengths were observed at λ = 572 nm (fwhm equals 47 nm, 1446 cm, 0.18 eV) for yellow-emitting Sr[LiAlO]:Eu and at λ = 554 nm (fwhm equals 49 nm, 1589 cm, 0.20 eV) for green-emitting Sr[LiGaO]:Eu. Sr[LiAlO]:Eu has excellent thermal quenching resistance with a photoluminescence emission intensity of >93% at = 423 K relative to the room temperature value, making this inorganic phosphor a potential candidate for solid-state lighting applications.