Determination of the exponent $ in the DPT of ferroelectric ceramics

Due to the experimental indetermination of the temperature T_max (ε′_max) because of the large broadening of the ε′ (T) maximum in ferroelectric ceramics, we have carried through computer programs by taking values of T_max in a ± 4°C interval of the experimental curves in order to get the best agreement for their paraelectric phase with the well known expression 1/ε′ = 1/ε′_max + A(T-T_max)$$, 1 < $$ $ltm 2, for diffuse phase transitions. The results we nave obtained for BaTiO₃, SBN (75/25), PLZT (40/60) and PLZT (65/35) ceramics show that the best fitting between experimental and computed points provides $$ values of 1.2 for BaTiO₃ and 1.99–2.0 for PLZT and SBN. At the same time it is possible to obtain the value of the temperature for ε′_max in a more precise way. Results are discussed according to different models for DPT in ferroelectric solid solutions.