Microwave dielectric properties of the ordered and disordered Pb(Sc1/2Ta1/2)O-3 ceramics

Microwave dielectric properties at similar to 35 GHz of B-site ordered (PST -O) and disordered with Pb-vacancies (PST-DV) relaxer ceramics Pb(Sc1/2Ta1/ 2)O-3 were investigated in the temperature range 100 + 550 K. The results w ere compared and fitted together with the new and earlier data in the 100 H z + 1 GHz range and recent data on infrared and submillimetre response (3-1 0(11) + 10(14) Hz). The dielectric response below polar phonon frequencies comprises two separate dispersion regions in both types of samples from whi ch only the lower frequency one (10(8) + 10(9) Hz) shows partial critical s lowing down. The basic role of the Pb disorder and ordered nano-clusters in the paraelectric phase is emphasized.