Nonlinear behavior of BNT-based lead-free piezoceramics under various ac fields

In this study, two different bismuth sodium titanate (BNT) based lead-free piezoelectric ceramics, BNKBT-5 and BNKLBT-1.5, were fabricated and their nonlinear piezoelectric behaviour were compared. The ac field dependent piezoelectric properties of both lead-free materials were investigated. An analysis of the changes in real parts of the materials parameters (e.g. stiffness, permittivity and electromechanical coupling coefficient) and the loss factors have been determined by model fitting and the complex material parameters can be found. Under a high ac field, BNKBT-5 and BNKLBT-1.5 have different nonlinear behaviour. This characterization is necessary for using the lead-free piezoelectric ceramics in high power transducer applications.