Structural evolution induced preferential occupancy of designated cation sites by Eu²⁺ in M₅(Si₃O₉)₂ (M = Sr, Ba, Y, Mn) phosphors
2016
Wei, Yi | Lin, Chun Che | Quan, Zewei | Molokeev, Maxim S. | Atuchin, Victor V. | Chan, Ting-Shan | Liang, Yujun | Lin, Jun | Li, Guogang
In this paper, we present new insight into a changing Eu²⁺ crystallographic site preference in Eu-doped M₅(Si₃O₉)₂ (M = Sr, Ba, Y, Mn), which is related to the structural variation induced by M cation substitutions. The effect of the local structural geometry on the luminescence properties of Eu²⁺ is revealed. By substitution of Ba²⁺ for Sr²⁺, the lattice expansion is restricted to specific cation sites, resulting in the abrupt blue shifted emission of Eu²⁺ ions. The abnormal blue shift on replacing Sr²⁺ with Mn²⁺ is attributed to the preferential 6-fold coordination for Mn²⁺ that moves the Eu²⁺ ions to other sites. The results elucidate the mechanisms of emission band adjustment by local site coordination change and it can be potentially extended to crystals which properties are sensitive to local lattice variations.
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