Synthetic method and luminescence properties of SrxCal1-xAlSiN3:Eu2+ mixed nitride phosphors

Single-phase Eu2+-doped SrxCa1-xAlSiN3 (0.2 <= x <= 0.8) red phosphor was obtained by nitridation of Ca1-x-ySrxEuy(Al-0.5, Si-0.5)(2) alloy powder under the high pressure of 190 MPa in a hot isostatic pressing apparatus at 2173 K. The unit cell volumes of the single phase expanded linearly with the increase in value of x from 0.2 to 0.8. A blueshift of the red emission peak of Eu2+ from 650 to 620 nm was observed by weakening the crystal field strength around the Eu2+ ion. SrxCa1-xAlSiN3:0.8 mol % Eu2+, with the optimum Eu concentration, showed high photoluminescence intensity over the whole range of x value from 0.2 to 0.8. Unlike nitrides of alkaline-earth or rare-earth metals, the intermetallic alloy powder was stable under ambient conditions and was thus suitable as starting material for red phosphors for industrial production. In x = 0.8 samples synthesized at 190 MPa, the same structure as CaAlSiN3, space group 36 (Cmc2(1)), was retained at unit cell volumes up to 289.92 angstrom(3), exhibiting the maximum solubility of Sr2+ in the solid solution, SrxCa1-xAlSiN3 (0 <= X <= 0-8). (C) 2008 The Electrochemical Society.