The article presents the results of research the pre-transitional features of the behavior of solid solutions based on lead zirconate-titanate. The presence of a “special” critical temperature Td on the temperature dependences of the permittivity 𝜀(T) and the remanent polarization Pr(T), preceding the temperature of the paraelectric phase transition at the Curie temperature TC, is noted. In the temperature range T < Td, the Pr(T) dependence obeys a power law. In the temperature range Td<T<TC, this law is not fulfilled. The results of X-ray experiments make it possible to associate this behavior with reversible disordering at T<Td of an ordered domain structure formed during the polarization of piezoelectric ceramics and with its irreversible disordering in the temperature range Td<T<TC. This is due to the appearance of internal mechanical stresses in a polycrystalline ferroelectric due to irreversible depolarization of the samples at temperatures Td<T<TC.The article presents the results of research the pre-transitional features of the behavior of solid solutions based on lead zirconate-titanate. The presence of a “special” critical temperature Td on the temperature dependences of the permittivity 𝜀(T) and the remanent polarization Pr(T), preceding the temperature of the paraelectric phase transition at the Curie temperature TC, is noted. In the temperature range T < Td, the Pr(T) dependence obeys a power law. In the temperature range Td<T<TC, this law is not fulfilled. The results of X-ray experiments make it possible to associate this behavior with reversible disordering at T<Td of an ordered domain structure formed during the polarization of piezoelectric ceramics and with its irreversible disordering in the temperature range Td<T<TC. This is due to the appearance of internal mechanical stresses in a polycrystalline ferroelectric due to irreversible depolarization of the samples at temperatures Td<T<TC.