Microwave dielectric properties of the ordered and disordered Pb(Sc½Ta½)o3 ceramics

Microwave dielectric properties at ∼35 GHz of B-site ordered (PST-O) and disordered with Pb-vacancies (PST-DV) relaxor ceramics Pb(Sc ½ Ta ½ )O 3 were investigated in the temperature range 100 ÷ 550 K. The results were compared and fitted together with the new and earlier data in the 100 Hz ÷ 1 GHz range and recent data on infrared and submillimetre response (3·10 11 ÷ 10 14 Hz). The dielectric response below polar phonon frequencies comprises two separate dispersion regions in both types of samples from which only the lower frequency one (10 8 ÷ 10 9 Hz) shows partial critical slowing down. The basic role of the Pb disorder and ordered nano-clusters in the paraelectric phase is emphasized.