HYPERFREQUENCY DIELECTRIC-RELAXATION IN FERROELECTRIC CERAMICS WITH COMPOSITION (BA1-YCAY)TIO3

Dielectric relaxation is reported for ceramics with composition (Ba1-yCa(y))TiO3 (0 less-than-or-equal-to y less-than-or-equal-to 0.2) in the frequency and temperature ranges 10(6) to 10(9) Hz and 250 to 450 K, respectively. Piezoelectric resonance frequencies F(r) are also determined on poled samples. A minimum of the relaxation frequency f(r) occurs close to the phase transition temperature either T(orth-tetr) or T(C). The composition variation of f(r) at room temperature is thus correlated with the various transition temperatures which are directly connected with the composition. The use of the lattice dynamical basis of Devonshire's theory has allowed to show the relaxation to be of dipolar type.