Crystal structure and luminescence properties of SrxCa1 - xAlSiN3:Eu mixed nitride phosphors

This study was performed to characterize the crystal structure and luminescence properties of Eu2+-doped SrxCa1 - xAlSiN3 (0.2 < = x < = 1) red phosphor. Structural refinement was carried out using the Rietveld method. The unit cell volumes were shown to expand linearly with increasing Sr content throughout the whole solid solution range. As an end member, SrAlSiN3:Eu2+ phosphor was synthesized under a high pressure of 190 MPa and high temperature of 2173 K. The phosphor crystallizes with an isotypic structure of CaAlSiN3 in the orthorhombic space group Cmc21 with lattice parameters of a = 9.8087(1) A, b = 5.75600(8) A, c = 5.16614(7) A, and unit cell volume = 291.674(7) A3. This unit cell volume was larger than that of CaAlSiN3:Eu2+ by 4%. The phosphor showed intense orange-red emission by 5d - > 4f transition of Eu2+ at around 610 nm. Through the whole range of solid solution, Eu2+-doped SrxCa1 - xAlSiN3 red phosphors showed a broad excitation band ranging from UV to visible light, and temperature characteristics comparable to those of CaAlSiN3:Eu2+ at the Eu concentration of 0.8 mol%.