Cation and anion ordering in Sr2Si7Al3ON13 phosphors

• Main Authors: King, Graham, Ishida, Kunio, Page, Katharine, Fukuda, Yumi, Albessard, Ariane Keiko, Hattori, Yasushi, Hiramatsu, Ryosuke, Mitsuishi, Iwao, Okada, Aoi, Kato, Masahiro, Fukushima, Noburu
• Format: Article
• Language: English
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c5tc00060b

A series of photoluminescent Ce 3+ doped samples with compositions close to Sr 2 Si 7 Al 3 ON 13 :Ce have been studied by neutron powder diffraction to determine the Si 4+ /Al 3+ and N 3− /O 2− site ordering. Contrary to a commonly held assumption that the edge sharing tetrahedral sites in this structure are occupied exclusively by Al 3+ , we find a partial occupancy of Al 3+ on these site but also an unexpected preference for Al 3+ to occupy 2 other tetrahedral sites which are only corner sharing. From the crystal structures and local structures, as determined by pair distribution function (PDF) analysis, we also find evidence for alternating Si-Al site ordering within the edge sharing chains as well as dimerization of the Si 4+ and Al 3+ cations within these chains. The O 2− are found to be partially ordered onto 2 of the anion sites, although small amounts of O 2− are found on other sites as well. The cation and anion ordering found by neutron diffraction is supported by theoretical calculations. Understanding cation and anion ordering is essential for optimizing the photoluminescence properties of this promising class of phosphor materials. A series of photoluminescent Ce 3+ doped samples with compositions close to Sr 2 Si 7 Al 3 ON 13 :Ce have been studied by neutron powder diffraction to determine the Si 4+ /Al 3+ and N 3− /O 2− site ordering.