Electrostrain Performance Study Of Bismuth Sodium Titanate-Based Ferroelectric Ceramics

Due to the excellent dielectric and ferroelectric properties,ferrcelectric ceramics are widely used in transducers、field of actuators and sensors.Bi_0.5Na_0.5TiO₃ ceramics,a typical lead-free piezoelectric ceramic with a high polarization and high electromechanical coupling coefficient,and has obvious advantages in electrostrain and application.In this text,the structural and electrical properties of BNT-based ceramics are systematically investigated by modulating them with Bi_0.5Na_0.5TiO₃ and through nonstoichiometric、B-site doping and A/B-site co-doping,and the results are summarized below:（1）BaTiO₃ doping of the BNT ceramic and regulate the BNT-BT ceramics to near the morphotropic phase boundary,then followed by the design of a nonstoichiometric for Bi³⁺/Na⁺.U.94Bi_0.5+xNa_0.5-xTiO₃-0.06BaTiO₃ lead-free ceramics were prepared by solid-state reaction method,their structural and electrical properties were systematically investigated.With increasing combine the dielectric relaxor plateau appears,which implies an extension of the R3c-P4bm coexistence temperature region;A non-polar to polar phase transition process occurs driven by the electric field,and found the 0.53%electrostrain when the x=0.02.It has been demonstrated that nonstoichiometric design can be effective in improving the electrostrain of ceramics.（2）To address the common high temperature ion precipitation problem of BNT ceramics,different components of excess Bi³⁺were designed and on this basis the BNT-based ceramics were B-site(Sr_1/3Nb_2/3)⁴⁺ doping,[(Bi_0.51Na_0.5)_0.93Ba_0.07]Ti_1-x(Sr_1/3Nb_2/3)_xO₃ lead-free ceramics were prepared using the solid-phase reaction method,and the results from structural and electrical tests showed that when(Sr_1/3Nb_2/3)⁴⁺ was introduced,and the dielectric relaxor plateau was appears,which offers the possibility of achieving high electrostrains,and a maximum electrostrain of 0.59%is found when x=0.01;in the x=0.0075 component a maximum ΔP was found,and a recoverable energy storage of 1.36 J/cm³ and an efficiency of over 60%was calculated.（3）The solid phase reaction method was used to prepare[Bi_0.51(Na_0.83K_0.17)_0.5]Ti_1-x(Mg_1/3Ta_2/3)_xO₃ lead-free piezoelectric ceramics and to test the structural and electrical properties of the samples.The results showed that at x=0.02 the ceramics were still in the normal ferroelectric phase,accompanied by a negative electrostrain of 0.14%at a positive electrostrain of 0.37%;at x≥0.04,the test results show a relaxor ferroelectric phase,which makes it difficult to form macroscopic polar driven by the electric field and therefore difficult to obtain large electrostrains.At x=0.08,a maximum electrostrain of 0.28%was obtained.This study provides data reference for the improvement of electrostrain and comprehensive properties of bismuth sodium titanate ferroelectric ceramics,laying a foundation for later application and enriching dielectric electrostrain theory.