Stable dielectric response in lead-free relaxor K0.5Na0.5NbO3–SrTiO3 thin films

Abstract

K 0.5 Na 0.5 NbO 3– SrTiO 3 (KNN–STO) thin films of different compositions were prepared by the chemical solution deposition method. While structural investigations confirmed the formation of perovskite solid solution in all developed films, dielectric experiments revealed a relaxor broad dispersive maximum in the sample with 15 mol% of STO, exhibiting for a thin film high ε′ ~ 330 at ~ 210 K. The history-dependent effects of this relaxor sample were compared to those of KNN–STO ceramics and, furthermore, shown to be much weaker than in widely used lead-based ferroelectric and relaxor ( Pb , La )( Zr , Ti ) O 3 ceramics: While fatigue endurance results revealed a slight drop in polarization after 3 × 105 switching cycles, the results of aging of the dielectric constant revealed no notable decrease in its values after 106 s.