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Abstract
Dielectric and other complementary measurements were carried out in order to confirm the AO-FR(LT)-FR(HT)-PC phase sequence and to determine the temperatures of each phase transition occurring in undoped PZT ceramics with Zr/Ti ratio 95/5 and Nb-doped ceramics with 0.25 ÷ 1 weight % of Nb2O5. These measurements revealed the diffused character of particular phase transitions and especially of the AO-FR(LT) one. The AO-FR(LT) and FR(LT)-FR(HT) phase transitions occur only in the part of sample volume in the vicinities of the determined temperatures of these transitions and the first one is extremaly broadened and extended towards the low temperatures in the remaining volume of the crystal. Temperature evolution of Raman spectra and the central peak revealed changes of the structure, frequencies and intensity of the scattered light in each phase transition.