Self Polarization in Pb(Sc1/2Ta1/2)O3 Relaxor Thin Films: Impact on the Dielectric and Piezoelectric Response

Abstract

The phenomenon of “self-polarization” was studied in chemical solution derived Pb(Sc1/2Ta1/2)O3 (PST) thin films on Pt/Si substrates. PST films exhibited field induced pyroelectric coefficients of 300 µC/(m2 K), with a detectivity figure of merit Fd=1.5×10-5 Pa-1/2 at 100 kV/cm bias fields. The piezoelectric coefficient d33 was found to saturate at a value of 60 pm/V at 100 kV/cm applied field and the electrostriction coefficient Q33 was found to be ∼0.025 m4/C2. The presence of self polarization was confirmed by piezoelectric and pyroelectric activity under zero applied bias fields, resulting in a pyroelectric coefficient of 50 µC/(m2 K), or an equivalent internal field of ∼25 kV/cm. The impact of this internal bias field on the dielectric constant at temperatures near the dielectric maximum corresponds to a ∼10% reduction in the dielectric constant. It is concluded that the “self-polarization” observed in relaxor PST films cannot be the origin of the order of magnitude reduction in the dielectric constant of thin films as compared to ceramics.