Cation and anion ordering in the layered oxyfluorides Sr3

Cation and anion ordering in the layered oxyfluorides Sr3-xAxAlO4F (A=Ba, Ca)

Prodjosantoso, A. K.; Kennedy, B. J.; Vogt, T.; Woodward, P. M.

The synthesis and structural characterization of mixed oxyfluorides of the type Sr3-xAxAlO4F is reported, where A is either calcium or barium. In these compounds the fluoride and oxide ions are ordered onto two distinct crystallographic sites. There is also an ordering of the alkaline earth cations over two crystallographic sites upon substitution of Ba2+ _or Ca2+_{for Sr}2+_{. The solid solubility limits extend to x~1 for substitution of} both barium and calcium, but the larger Ba2+ _{cations show a strong site} preference for the ten-coordinate strontium sites, while the smaller Ca2+ _{cations prefer the eight-coordinate strontium sites.}

DOI: 10.1016/S0022-4596(02)00128-7