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

Abstract

K0.5Na0.5NbO3–SrTiO3 (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)O3 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.

Keywords

• Lead-free ceramic thin films
• relaxor ferroelectrics
• electrical fatigue and aging