Enhancing the tunability properties of pure (Ba,Sr)TiO3 lead-free ferroelectric by polar nanoregion contributions

In the present work, series compositions of (Ba1−xSrx)TiO3 (0 ≤ x ≤ 0.4) lead-free ferroelectric (BST) were successfully prepared by sol–gel method. The effects of Sr2+ on the optical properties, crystal structure and morphology of BaTiO3 were systematically investigated. Compositions with x < 0.4 exhibit single-phase tetragonal perovskite at room temperature, while a cubic structure of BST has been detected in the ceramic with x = 0.4. Phase transition temperature was shifted toward lower temperature by increasing Sr doping. Moreover, a detailed tunability analysis for the present ceramics confirmed an enhancement upon Sr addition and the maximum values were observed at Sr = 0.2. The enhancement back to present multiple components contribute to the DC field-induced dielectric constant, where at low electric fields the Langevin theory indicates present polar nanoregion (PNR) contributions to tunability data; however, domain switching contributions at high electric field was described by Johnson equation. Ferroelectric properties appraised by P–E loop and positive-up negative-down (PUND) methods have been introduced. The results showed that the remnant polarization appraised by PUND method is much lower than polarization estimated by P–E loop indicating that the different values of Pr are mostly owing to leakage current contribution in P–E method.