Preparation And Performance Of Bismuth Sodium Titanate Based Electrostrictive Ceramics

Bi_1/2Na_1/2TiO₃?BNT?–based lead–free materials show the potential to be the substitute materials for lead–containing materials in piezoelectric actuators fields due to their excellent electrostriction.In this paper,(Bi_0.5Na_0.5)TiO₃–Ba TiO₃ binary system?abbreviated as BN T–BT?was chosen as the basic material,while B–site complex ions,new A?A??BO₄ composite oxides and multiferroic materials were selected as the dopants.We have studied the phase transition and properties of the material,and obtained the large electrical strain response of the material.The main results can be summarized as follows:1.The effects of B–site complex ions(Al_1/2Sb_1/2)⁴⁺,(Mn_1/2Sb_1/2)⁴⁺,(Ni_1/2Sb_1/2)⁴⁺and(Fe_1/2Sb_1/2)⁴⁺doping BNT–BT–based ceramics on phase structure,microstructure and electrical properties were systematically studied.The result indicates that a ll doped ceramics possessed pure perovskite phase structure.The addition of B–site complex ions induced ferroelectric to relaxor phase transformation,the coexistence of ferroelectric and relaxor phase promoted the improvement of strain.As the molar ratios of(Al_1/2Sb_1/2)⁴⁺,(Mn_1/2Sb_1/2)⁴⁺,(Ni_1/2Sb_1/2)⁴⁺and(Fe_1/2Sb_1/2)⁴⁺are 0.015,0.015,0.005 and 0.015,the best strain value of the material is obtained,the value of unipolar strain reaches 0.46%,0.48%,0.37%,0.38%at 80 kV/cm respectively,equivalently a large signal d^*₃₃(S_max/E_max)of 573,602,463,475 pm/V.The properties can be comparable to that of lead based materials.The electrostrain performance of BN T–BT ferroelectric ceramics at high temperature changes with temperature showed that the ferroelectric phase of material at room temperature in the ferroelectric–relaxor phase transition temperature(T_F-R)can be induced into relaxor phase structure,and relaxor phase changed into ferroelectric phase under the electric field,thus showing that temperature induced large strain.The above results show that the high electroinduced strain of the BNT–based material is derived from the transition from the relaxor phase to the ferroelectric phase induced by the electric field.In addition,the dielectric peaks broadened and ceramics showed typical relax–behavior at room temperature with high content of complex ions doping.2.The effects of new A?A??BO₄ composite oxides doping BN T–BT–based ceramics on phase structure,dielectric properties,electric–field induced strain performance and temperature stability were investigated.In the compositions range studied,CaYAlO₄?CYAO?has diffused into BNT–BT–based ceramics to form a pure perovskite structure,and the doping of C YAO destroyed the ferroelectric lo ng range order of BNT–BT–based ceramics showing that the phase transition temperature of ferroelectric phase–relaxation phase is transferred to the room temperature which induced the appearance of relaxor phase and thus improved the strain of ceramics.A large strain:S_{m ax}=0.44%,equivalently a large signal d^*₃₃ of 470 pm/V was achieved at x=0.012.3.The effects of multiferroic materials Er₂CoMnO₆?ECMO?doping on phase structure,electrostrain properties,temperature stability and fatigue properties of BNT–BT–based ceramics were investigated.The results show that all ceramics exhibit perovskite structures and ECMO induces the transformation of the tetragonal phase to the pseudopotential phase,corresponding to the transformation of ferroelectric phase to the relaxation phase,which further improves the electrical strain properties of the material.At x=0.009,the maximum strain value was obtained:S=0.43%,d^*₃₃=550 pm/V.What's more,the material has excellent fatigue resistance.When the electr ic field circulated 10⁵ times,the electrical strain properties of the material almost unchanged,which is superior to the traditional lead based materials.Therefore,as a potential environmental friendly lead–free material system,the material has wide application prospects in piezoelectric actuators and other devices.