Apatites and britholites, are they akin - as probed by Eu3+luminescence?

Britholite, a relatively little known cousin of the celebrated apatites, has been prepared by solid-state reaction methods. In samples of hexagonal Y 6- x Ca 4 (SiO 4 ) 6 F 2 :Eu 3+ x ( x = 0.5-4%) britholite prepared by using Eu 3+ luminescence as a local probe, we found that there are two kinds of cationic site, in the same way as for the apatites. But these two sites appear to have nearly the same local symmetry, which is considerably different from the case for the fluoro-apatite counterpart.