Study On Preparation And Properties Of BNT Based Lead Free Piezoelectric Ceramics Doped With Multiferroic Materials

PZT lead piezoelectric ceramics has long occupied an important position of piezoelectric ceramic materials,with the progress of society,people’s awareness of environmental protection,research and development of lead-free piezoelectric ceramics with high performance is an important research topic.Bi_0.5Na_0.5Ti O₃（BNT）piezoelectric ceramics have become one of the most promising substitutes for lead based piezoelectric ceramics due to their excellent piezoelectric and dielectric properties.In this paper,0.935Bi_0.5Na_0.5Ti O₃-0.065BT（BNT-BT6.5）was modified by ion doping and adding new components in two ways:（1）A single perovskite structure was obtained from BNT-BT6.5 lead-free piezoelectric ceramics by Sr₃Cu Nb₂O₉ doping of multiferroic materials.Around criticalcomposition（x=0.003）at a driving field of 60 k V/cm,the coercive field（E_c）is18.41 k V/cm,the remnant polarization（P_r）is 29.11μC/cm²,a large unipolar strain of 0.29%witha normalized strain(d^*₃₃=483 pm/V)is obtained at room temperature.（2）0.994BNTBT-0.006SCN ceramics have excellent energy storage properties and obvious relaxation behavior.As theelectric field increased,the nonlinearity of P-E loops increasedgradually and the maximum polarization was improved from 7.5μC/cm² to 34.05μC/cm² with the applied electric field increasing from 20 k V/cm to60 k V/cm.Theenergy storage density（W₁）reaches 0.62 J/cm³ and the Energy storage efficiency（η）is 0.54 under at 60 k V/cm.（3）A single perovskite structure was obtained from BNT-BT6.5 lead-free piezoelectric ceramics by Bi Mn O₃ doping of multiferroic materials.The addition of Bi Mn O₃ can obviously promote the growth of grain,and make the grain boundary more obvious,the grain is full and round,the porosity is reduced,and the density of ceramics increases.When x=0.015,The piezoelectric constant d₃₃ is 210 p C/N,the electromechanical coupling coefficient K_p is 0.41,the dielectric constantεis 1880,the dielectric loss tanθis 0.020。（4）(Fe_1/2Ta_1/2)⁴⁺substituted B-site of BNT-BT6.5 lead-free piezoelectric ceramics,all the samples formed a single pure perovskite structure.By SEM analysis,with the increase of FT doping amount,the grain size increases first and then decreases,and the grain boundary becomes more obvious,and the porosity decreases,which leads to the formation of piezoelectric ceramics with high density.When x=0.006,the grain size is the largest about 3μm⁶μm,d₃₃=225 p C/N,K_p=40%,ε=1500,tanθ=0.025.With the increase of FT doping,the coercive field decreases and the remanent polarization increases first and then decreases.When x=0.006,E_c=30k V/cm,P_r=33.19μC/cm².（5）BNT-BT6.5-PZT composite piezoelectric ceramics through the XRD analysis,when the PZT content is less than 0.09,the samples are formed a single pure perovskite structure,and PZT effectively diffused into the BNT-BT6.5 solid solution.By SEM analysis,with the increase of PZT content,the grain size increases gradually,the uniformity of the grain size is increased,the porosity decreases,the density increases,and the angular grains appear.When x=0.06,d₃₃=195 p C/N,K_p=40%,ε=1734,tanθ=0.026.