Structural Chemistry of M 2Si5N8: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 M 2Si5N8: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 M 2Si5N8: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 Pmn21 (No. 31) with Z = 2, a = 5.7424(1) Å, b = 6.8837(1) Å, c = 9.3586(1) Å, and α(= β = γ) = 90°.
Document Type: Research Article
Publication date: April 1, 2012
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