Field Strain-induced Properties Of Bismuth Sodium Titanate Lead-free Ferroelectric Ceramics

Piezoelectric drives have the advantages of fast response,high positioning accuracy,and small size,and have received extensive attention in the field of precision drives.Lead-based piezoelectric drivers dominate the commercial market,however,due to limitations in the use of the harmful element lead,there has been a trend to develop lead-free piezoelectric materials and driver alternatives.Among them,sodium bismuth titanate(Bi_0.5Na_0.5)Ti O₃（BNT）,as a typical perovskite relaxor ferroelectric with ultra-high field-induced strain,is considered to be the most promising alternative to lead-based systems.One of the lead systems.However,compared with lead-based ceramics,BNT-based ceramics have disadvantages such as higher driving voltage,larger hysteresis,and poor temperature stability.In view of the above problems,this paper optimizes the phase structure and grain structure of sodium bismuth titanate-based ferroelectric ceramics through component design and structural control to improve the strain performance of ceramics.The main contents are as follows:（1）（1-x）{0.76(Bi_0.5Na_0.5)Ti O₃-0.24Sr Ti O₃}-x Na Nb O₃（BNT-ST-x NN,x=0-0.03）solid solution ceramics were prepared by solid-state reaction method to achieve depolarization The temperature T_d is lowered below room temperature,resulting in the coexistence of room temperature non-ergodic/ergodic relaxation phases.The results show that when x=0.01,the ceramic is at the non-ergodic/ergodic relaxation phase boundary,and the electric field-induced relaxation-ferroelectric phase transition produces a large field-induced strain of the ceramic,that is,at E=4 k V/mm,the strain it reaches 0.278%,and the equivalent piezoelectric coefficient d₃₃*reaches695 pm/V.（2）The NN templates synthesized by the molten salt method successfully induced the texture of BNT-ST-x NN（x=0.01-0.03）ceramics.The results show that for the BNT-ST-x NN（x=0.01-0.03）textured ceramics prepared by the casting method,with the increase of x,the texture degree F increases from 69%to 87%,and the strain increases to more than0.3%,compared with the non-textured ceramics,the strain increases by6.4%～38.7%,and the hysteresis decreases.Among them,the BNT-ST-0.03NN textured ceramic in the ergodic state of various states has both large strain（～0.3%）and low driving electric field（4 k V/mm）,and at the same time d₃₃*reaches 518 pm/V at a higher temperature,which is expected to be used as a high-temperature piezoelectric drive device.51 figures;6 tables;101 references...