Microstructure And Electrical Properties Of BCZT-base Lead-free Piezoelectric Ceramics After Doping Modification

(Ba,Ca)(Zr,Ti)03(abbreviated as BCZT) based lead-free piezoelectric ceramic is a kind of excellent ferroelectric ceramic, which is substituted by A and B-site ion on BT based ceramic. In this thesis, BCZT-base lead-free piezoelectric ceramic was successfully prepared by conventional solid-state sintering technique to obtain the superior electrical properties. The influence of SnO2, Bi2O3, TbDyFe, Li2 CO3 dopant on microstructure, phase structure and electrical properties of BCZT-base lead-free piezoelectric ceramics were investigated. The main conclusions are as follows:(1)The influence of the SnO2 doping on phase structure, electric properties and dielectric relaxor of the (Ba0.85Ca0.15)(Ti0.9Zr0.1-xSnx)O3 (x=0.02,0.04,0.06,0.08 mol) (abbreviated as BCZT-Sx) were investigated. The experimental results show that all samples posses a pure perovskite structure. TR-t exists on room temperature nearby from rhombohedral to tetragonal structure. When the content of SnO2 increases, the Curie temperature (Tc) and TR-T gradually shifts to lower temperature. Besides, the dispersion coefficient y of the ceramic is 1.76, which shows the typical dispersed transformation and dielectric relaxor. BCZT-Sx ceramic obtains the excellent properties when x=0.02 mol:d33= 553pC/N, kp= 49%, ?r?6045(1kHz), tan ?-1.7%(1kHz), Pr=5.45 ?C/cm2, Ec=2.2 kV/cm.(2)The influence of the Bi2O3 doping on the microstructure, phase structure and electric properties of (Ba0.85Ca0.15)(Ti0.9Zr0.08Sn0.02)O3-xBi2O3 (x=0,0.02,0.04,0.06,0.08 wt.%) (abbreviated as BCZTS-xBi) were investigated. The results indicate that all the samples emerge a pure perovskite phase structure diffraction peak. When the content of Bi2O3 increases, the grain size becomes smaller and relatively homogeneous. The results of dielectric properties indicate that the Curie temperature (Tc) shifts to higher temperature after doping Bi2O3. And BCZTS-xBi ceramic obtains the excellent properties when x=0.02 wt.%:d33= 430 pC/N, kp= 41%, ?r-3844 (1kHz), tan ?-1.8%(1 kHz), Pr=6.67 ?C/cm2, ?=3.65 kV/cm.(3)The influence of the TbDyFe doping on the microstructure, phase structure and electric properties of (Ba0.85Ca0.15)(Ti0.9Zr0.08Sn0.02) O3-xTbDyFe (x=0.1,0.2,0.3,0.4 wt.%) (abbreviated as BCZTS-xTbDyFe) were investigated. The results indicate that all the samples posses a typical perovskite structure solid solution. The microstructure exhibits relatively homogeneous, and pores are none found in the grain boundary. Besides, doping TbDyFe causes the fall of the Curie temperature (Tc). BCZTS-xTbDyFe ceramic obtains excellent properties when x=0.1 wt.%:t/33= 500 pC/N, kp= 40%, ?r-5955 (1 kHz), tan ?-1.9%(1 kHz), Pr=6.6 ?C/cm2, Ec=2 kV/cm.(4)The influence of the Li2 CO3 doping on the microstructure, phase structure and electric properties of 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3-x Li2 CO3 (x=0.5,1, 2 and 3 wt.%) (abbreviated as BCZT-xLi) were investigated. From the XRD patterns of BCZT-xLi, all samples are of typical perovskite phase when x<2 wt.%. However, When x>2 wt.%, the appearance of secondary phase can be clearly observed in the XRD patterns. It is found that Li+has a limited solubility in BCZT ceramic. From the SEM of BCZT-xLi ceramics, all samples have homogeneous microstructure, and porosity is almost not found in the grain boundary. BCZT-xLi ceramic obtains excellent properties when x= 0.5 wt.%:d33= 164 pC/N, kp= 44%, ?r-2365 (1 kHz), tanS-1.78%(1 kHz).