Neutron diffraction study of the Pb1−xAlxF2+x solid solution

Powder neutron diffraction studies have been carried out on the fluorite-type Pb1−xAlxF2+x (0≤x≤0.12) solid solution. Three interstitial sites, F′, F′′ and F′′′, were observed, in addition to the normal Fn sites of the fluorite structure at (1/4,1/4,1/4). Four types of fluoride sites, Fn, F′, F′′ and F′′′, were identified with the four sublattices (Fn)Pb, (Fra)Al, (Fi)Pb and (Frd)Al suggested from 19F- and 27Al-NMR investigations. The clustering process proposed in Pb1−xAlxF2+x on the basis of NMR results is confirmed and the cluster characteristics are determined.