Effect Of Composite Doping On The Microstructure And Electrical Property Of BCZT Lead-free Piezoelectric Ceramics

Piezoelectric ceramics are widely used in the field of medical imaging,sensors,transducers and ultrasonic motors etc.Piezoelectric ceramics are divided into lead-based and lead-free piezoelectric ceramics.Lead-free piezoelectric ceramics meet the requirements of sustainable development of environmental-friendly society because of their absence of lead.In the dissertation,on the basis of(Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃?BCZT?-based lead-free piezoelectric ceramics,the composite doping modification and preparation technology are used to improve the comprehensive electrical properties of piezoelectric ceramics.1.The effect of Co₂O₃ doping on the phase structure,microstructure,piezoelectric property and dielectric property of BCZT ceramics is investigated.Without doping of Co₂O₃,the electrical property of sample is as follows:piezoelectric coefficient d₃₃=420 pC/N,plane electromechanical coupling coefficient k_p=40%,dielectric constant?_r=4200,dielectric loss tan?=1.7%;With the increase of Co₂O₃ doping amount,the grain size,d₃₃,k_p and tan?decrease,while?_r increases.It is found all samples have pure perovskite phase structure.2.The effect of conventional solid phase sintering?CS?method and microwave sintering?MWS?method on the phase structure,microstructure,piezoelectric property,dielectric property and ferroelectric property of(Ba_0.85Ca_0.15)(Ti_0.9Zr_0.08Sn_0.02)O₃?BCZTS?lead-free piezoelectric ceramics is searched.The results show that the structure of samples is of pure perovskite under CS and MWS.At the same sintering temperature,the grain size of samples prepared by MWS are superior to the samples prepared by CS.At 1380?,both the samples prepared by CS and MWS obtain the best electrical properties.The Curie temperature and the piezoelectric property of the samples prepared by MWS are obviously better than that of CS,but the dielectric and ferroelectric property of the samples prepared by MWS are inferior to CS.3.The effect of precursor SrTiO₃ doping on the phase structure,microstructure,piezoelectric property,dielectric property and ferroelectric property of(Ba_0.85Ca_0.15)(Ti_0.9Zr_0.08Sn_0.02)O₃?BCZTS?ceramics is investigated.The results show that there are some impurity phases when the doping amount of precursor SrTiO₃ is 5 wt.%,20wt.%,40 wt.%and 50 wt.%respectively.When the doping amount of precursor SrTiO₃ is 20 wt.%,there is almost no porosity in sample,the ferroelectric property of sample is optimized:P_r=13.99?C/cm²,E_c=1.64 kV/cm.However,there is no impurity phase when the content of precursor SrTiO₃ is 10 wt.%and 30 wt.%.Moreover,their ferroelectric property is inferior to samples with impurity phase.4.The effect of precursor SrTiO₃ doping on the phase structure,microstructure,piezoelectric property and dielectric property of BaTiO₃ lead-free piezoelectric ceramics doped with Na₂CO₃ and Bi₂O₃?NBBT?is explored.The results show that there are some impurity phases when the doping amount of precursor SrTiO₃ is 10wt.%,20 wt.%and 30 wt.%respectively.However,the impurity phases disappear when the doping amount of precursor SrTiO₃ is 40 wt.%and 50 wt.%respectively.While the doping amount of precursor SrTiO₃ is 40 wt.%,the porosity of sample almost disappears,the Curie temperature of sample becomes highest T_c=237?.