STRUCTURE ORDERING EFFECTS IN LEAD CONTAINING CERAMIC PEROVSKITES

The studies of ordering effect on properties of lead-containing perovs kite solid solutions PST, PSN and PLZT are reported. The properties de termining response of the materials to the change of external factors (temperature, electric field) are discussed as a result of structural rearrangements caused by composition, technological treatment, high-en ergy radiation, and ambient conditions. The different behaviour of the ordering parameter observed in PST and PSN systems is explained as a result of the different temperatures of synthesis with respect to the temperature of structural order-disorder phase transistion of the syst ems. The dependence of dielectric permittivity on time after the chang e of temperature or electric field in PLZT is investigated. At every t emperature the dielectric properties are characterized by unique epsil on'(t) independently of previous thermal history. The defect stimulate d phase transformation and pronounced broadening of the region of phas e transition in neutron irradiated PLZT 6.5-8.5/65/35 ceramics is obse rved and is equivalent to the increase of the La-content in the compou nd.