Preparation And Properties Of BF-BT-BZT High Temperature Lead-free Piezoelectric Ceramics

High temperature piezoelectric ceramics are widely applied in aerospace,nuclear energy,petroleum exploration,automobile and other fields,which have important research significance.Lead zirconate titanate ceramics?PZT?play an important role in the field of piezoelectric ceramics because of their strong piezoelectric activity and good temperature stability.Whereas,PZT ceramics are harmful to the environment and health during processing,and its application in the high temperature field is also limited by its low depolarization temperature.Bi_0.5Na_0.5Ti O₃ and K_0.5Na_0.5Nb O₃ based ceramics have high Curie temperature and are attracting attention in recent years.Unfortunately,the temperature stability is not sufficient for high temperature applications.BiFeO₃?BF?is a promising high temperature ferroelectric material with T_C=830?.More recently,?1-x?BF-x BT?BFBT?system has drawn a much attention as a potential lead-free piezoceramics.In this experiment,Li₂CO₃ was added as a sintering aid,the stoichiometric ratio of BF/BT was changed,and Bi(Zn_0.5Ti_0.5)O₃ was doped for ion substitution to improve the piezoelectric,dielectric,ferroelectric performance and temperature stability of the piezoelectric ceramics.The phase transition,microstructure,electrical properties and high temperature stability of the ceramics were studied in this paper.The research content is as follows:?1?The BiFeO₃-Ba Ti O₃-Bi(Zn_0.5Ti_0.5)O₃+x Li₂CO₃?where x=0,0.1,0.2,0.3,0.4mol%,abbreviated as BFBT-BZT-x LC?lead-free piezoelectric ceramics with high Curie temperature and high temperature stability were made by refined solid-state reaction approach.Experimental results demonstrate that piezoelectric properties and temperature stability of BFBT-BZT-x LC piezoelectric ceramics were significantly improved by adding Li₂CO₃ sintering additives.What's more,when x=0.3 mol%the ceramics sintered at970?,the results show the optimal electrical properties with d₃₃=184 p C/N.In particular,high Curie temperature?T_C=554??and high depolarization temperature(T_d=530?,d₃₃=150 p C/N)were obtained.?2?The?1-x?BiFeO₃-x Ba Ti O₃-Bi(Zn_0.5Ti_0.5)O₃+Mn O₂+Li₂CO₃?where x=0.24,0.26,0.28,0.30,0.32,0.34,abbreviated as?1-x?BF-x BT-BZT?ceramics were prepared.When x=0.3,the piezoelectric performance,Curie temperature,and depolarization temperature are as high as 184 p C/N,550?,530?,respectively.The coexistence of rhombohedral and pseudocubic phases in the ceramic structure.It is considered that the morphotropic phase boundary was formed at x=0.3.It is worth noting that when x=0.24,the ceramics have a high T_c=580?and low dielectric loss tan?=1.9%.?3?In the experiment,the compound ion(Zn_0.5Ti_0.5)³⁺was used for B-site ion substitution.The 0.76BiFeO₃-0.24Ba Ti O₃-x Bi(Zn_0.5Ti_0.5)O₃+0.0035Mn O₂+0.3mol%Li₂CO₃?where x=0,0.015,0.020,0.025,0.030,abbreviated as BF-BT-x BZT?piezoelectric ceramics were prepared.BZT can form a new ternary perovskite solid solution with BF-BT piezoelectric ceramics.This phenomenon improves the piezoelectric performance and temperature stability of BF-BT-x BZT ceramics effectively.The research results show that with the increase of the BZT content,the crystal structure of the ceramic samples has not changed much,and all samples are rhombohedral phase.When BZT is 0.02,0.76BF-0.24BT-x BZT high temperature lead-free piezoelectric ceramics has the best piezoelectric performance,where d₃₃=102p C/N,k_p=0.35,Q_m=73.29 respectively.It is worth noting that when x=0.02,the dielectric loss of the ceramic is 1.8%.It shows that the aging rate of the ceramic is extremely low and the ceramic can be applied in practical fields.When the BZT content is 0.02,the T_C reaches the maximum value of 595?.The depolarization temperature T_d=560?,at such a high depolarization temperature,the piezoelectric constant is still as high as 84p C/N.In this experiment,a simple preparation process and low preparation cost were used to develop the lead-free piezoelectric ceramics with good piezoelectric performance and extremely high temperature stability.This is conducive to the industrial production of ceramics,and the practical application of the ceramics in the field of high temperature becomes possible.