Study On The Structure And Electrical Properties Of Rare Earth Ion Doped BT-based Lead-free Piezoelectric Ceramic

Lead zirconate titanate[Pb（Zr,Ti）O₃]piezoceramics with superior electrical properties and temperature stability,have been utilized in numerous electronic devices（e.g.,sonar motors,ultrasonic motors,sensors,transducers,etc.）owing to their ability to transform electrical and mechanical energy.Nevertheless,Pb-based piezoceramics contain more than 60%Pb oxide,which may harm human health and pollute the ecological environments.Therefore,the development of Pb-free piezoceramics to substitute Pb-based components in various electronic devices is one of the significant measures to achieve sustainable development.In this thesis,the modified barium titanate（BaTiO₃）based Pb-free piezoceramics were prepared using chemical modification（rare earth ion doping）,and their phase structure,microstructure and electrical properties were systematically researched.The relevant research results are as follows:（1）The（1-x）(Ba_0.94Ca_0.06Ti_0.92Sn_0.08)-x Sm₂O₃-0.06mol%Ge O₂（0 mol%≤x≤0.09 mol%）[abbreviated as（1-x）BCTS-x Sm-0.06G]Pb-free piezoceramics were synthesized via a conventional solid-state method.The influences of Sm₂O₃ doping on the phase structure,microstructure and electrical performances of BaTiO₃-based piezoelectric ceramics were researched.The research demonstrates that the ceramics form a morphotropic phase boundary（MPB,O-T）and obtain a large number of nano-ferroelectric domains when Sm₂O₃=0.03 mol%,thus obtaining favorable electrical properties:d₃₃=630±20 p C/N,k_p=61%,T_C=63.5°C,ε_r=4906,tanδ=3.25%,P_r=10.39μC/cm²,E_C=1.02 k V/cm.（2）The（1-x）(Ba_0.98Ca_0.02Ti_0.94Sn_0.04Zr_0.02)-x Y₂O₃（0 mol%≤x≤0.1 mol%）[abbreviated as（1-x）BCTSZ-x Y]lead-free piezoceramics were fabricated via a conventional solid-state method.The effects of Y₂O₃ doping on the phase structure,microstructure and electrical performances of BaTiO₃-based piezoceramics were researched.The research indicates that the ceramics form MPB（O-T）and gain a relatively dense grain distribution when Y₂O₃=0.06 mol%,thereby gaining favorable electrical performances:d₃₃=419 p C/N,k_p=52%,T_C=89°C,ε_m=26900,tanδ=2.86%,P_r=14.41μC/cm²,E_C=1.8 k V/cm.（3）The six kinds of rare earth oxide were doped to BCTSZ ceramics via a conventional solid-state method,the（1-x）(Ba_0.98Ca_0.02Ti_0.94Sn_0.04Zr_0.02)-x M₂O₃（0mol%≤x≤0.12 mol%,M=Y,La,Ce,Pr,Nd,Sm）lead-free piezoceramics were fabricated.The effects of six kinds of rare earth oxide doping on the phase structure,microstructure and electrical performances of BaTiO₃-based piezoceramics were researched.The results indicate that the MPB（O-T）were formed in ceramics when Nd₂O₃=0.06 mol%.Compared with other rare earth oxides,the ceramics with this composition also obtain larger grain size and more nano ferroelectric domains.Its electrical properties are as follows:d₃₃=463 p C/N,k_p=56%,T_O-T=36.5°C,T_C=87.5°C,ε_r=3720,tanδ=2.07%.