title: Structural chemistry of M2Si5N8:Eu2+ (M = Ca, Sr, Ba) phosphor via structural refinement.
abstract: Structural refinement using X-ray powder diffraction data and geometry energy calculations using quantum mechanics were used to investigate the preferential substitution sites and the amount of Eu2+ ions in the host lattice of alkaline earth elements co-doped M2Si5N8:Eu2+ (M = Ca, Sr, and Ba), which is a red color-emitting nitride phosphor prepared via a carbothermal reaction method. Of the possible preferential sites, the preferential site proposed by the structural refinement results, in which the Eu2+ ions might preferentially occupy nine coordinated sites with nitrogen in M2Si5N8:Eu2+, was confirmed via geometry energy calculations using a first-principle based on the density-functional theory. The final converged weighted R factor (R(wp)) and the goodness-of-fit indicator [S(= R(wp)/R(e))] were 9.51% and 1.77, respectively. Each occupancy of Eu2+ ions for the two non-equivalent M sites, M(1) and M(2), was 0.10(2) and 0.04(2), respectively. The final refined model described the crystal structure in a space group Pmn2, (No. 31) with Z = 2, a = 5.7424(1) angstroms, b = 6.8837(1) angstroms, c = 9.3586(1) angstroms, and alpha(= beta= gamma)= 90 degrees.
authors: Korea Research Institute of Standards and Science, 209 Gajeong, Yuseong, Daejeon 305-340, Korea.
authors: Yong-Il
authors: YI
authors: Kim
authors: Kwang Bok
authors: KB
authors: Kim
authors: Yun-Hee
authors: YH
authors: Lee
authors: Ki-Bok
authors: KB
authors: Kim