Abstract
Dielectric susceptibility data are presented for frequencies between 10 and 109 Hz and for several Li concentrations. A low-frequency relaxation peak is attributed to an impurity mode slowing down to below 1 Hz at a concentration-dependent temperature. For Li concentrations xor=0.06 exhibit disorder features that cannot be attributed to glass models nor to ferroelectricity. Non-random occupation of lattice sites by impurities could be at the origin of these features.