【作者】 冯铁程；

【导师】 吴裕功；

【作者基本信息】 天津大学 ， 微电子学与固体电子学， 2010， 博士

【摘要】 本文借助B位先驱体法在750℃合成了亚稳态钙钛矿型PZT粉料,在烧结过程中,过量ZrO₂随着温度的升高逐渐析出使整个体系趋向热力学稳定状态,从而形成PZT/ZrO₂复合压电陶瓷材料。研究了四方和三方不同铁电相区域,Nb⁵⁺离子软性掺杂和无掺杂情况下,第二相ZrO₂粒子引入对PZT基体各种性能的影响。研究中应用了XRD、SEM、TEM、EDS等研究手段,详细分析了第二相ZrO₂粒子的析出温度、析出范围和析出形貌等。结果显示,在Nb⁵⁺软性掺杂的情况下在ZrO₂名义含量值a>0.03时XRD检测到单斜相或四方相ZrO₂存在,在无掺杂的三方铁电相区1260℃烧结温度下,在名义ZrO₂含量最大值a=0.05时仍然没有检测到ZrO₂存在,这都说明了PZT本身对铅缺少容忍不同会造成一定的Zr/Ti比例偏移富锆方向。在Zr/Ti比例偏移的情况下,电学性能的变化趋势由PZT本身性质决定;在ZrO₂明显析出时,电学性能如d₃₃,K_p等有不同程度的下降,但在a=0.05时d₃₃值仍然能保持a=0.00时的90%。随着名义ZrO₂含量值a的增大,断裂韧性K_IC均有一定的提高,但是四方铁电相区域（51/49）K_IC增加幅度（14%）远小于三方铁电相区域（58/42）K_IC增加幅度（62%）。三方铁电相区域四方相ZrO₂的存在是其K_IC增加幅度很大的主要原因之一。断裂强度σf除了在四方铁电相区ZrO₂析出时有一定程度下降外均升高,这和烧结密度、晶粒尺寸等有一定的关系。由于PZT基体和ZrO₂颗粒的物理性质,如弹性模量或者泊松比等差异,在降温过程中引起热失配,残余应力保留在烧结体中。PZT基体受压应力,第二相ZrO₂颗粒受拉应力,但实际烧结体中应力类型和大小与ZrO₂颗粒析出状态有关。如Zr/Ti比例为58/42时,由于四方相ZrO₂的存在,PZT基体中保留的压应力使居里温度降低;而Zr/Ti比例为51/49时,只有单斜相ZrO₂存在,由于马氏体相变和应力释放等原因,居里温度反而上升。通过介电-温谱分析,第二相ZrO₂的存在使四方铁电相区域PZT弥散程度加强,使三方铁电相区域PZT弥散程度减弱。更多还原

【Abstract】 Metastable PZT solid solution powders of perovskite structure are synthesized by B-site precursor method at 750℃. With the increase of temperature, addition of ZrO₂ will precipitate from matrix of PZT because of systems becoming more stable state in thermodynamics, thus PZT/ZrO₂ Piezoelectric ceramic composite was prepared. The effect of ZrO₂ addition on mechanical and piezoelectric properties of composites was investigated in different ferroelectric areas from rhombohedral phase to tetragonal phase and Nb5+ ion-doped.Precipitated temperature, range, micrographs of ZrO₂ second phase were studied by using analysis methods such as XRD, SEM, TEM, EDS etc. The results showed that monoclinic or tetragonal zirconia presented when nominal addition of ZrO₂ over 0.03mol/PZNT mol by using XRD studies. There is no zirconia phase in pure PZT （Zr/Ti=60/40） sintering at 1260℃until nominal addition of ZrO₂ over 0.05 mol/PZT. From above we can see that a certain shift of Zr/Ti happened because of tolerance of Pb absence in PZT.The change of electric properties is up to PZT self when the shift of Zr/Ti happened. Electric properties such as d₃₃ and K_p have a little decrease due to the second phase of ZrO₂, but the value of d₃₃ at a=0.05 reaches the ninety percent of the value at a=0.00. Fracture toughness K_IC increases in both rhombohedral phase （62%） and tetragonal phase （14%） with the increase of ZrO₂ nominal value a. The bigger extent of increase in rhombohedral phase is the presence of tetragonal ZrO₂. Fracture strengthσf also increased except in tetragonal phase, this is related to the density and grain size and so on.There is thermal stress in sintering body because of the mismatch of physical properties such as elastic modulus or poisson ratio between matrix and particle. Compressive stress in PZT matrix and tensile stress in ZrO₂ particle, but real instance is decided to the precipitation state of ZrO₂. For example, Curie temperature decreased when Zr/Ti is 58/42, but increased when Zr/Ti is 51/49. The reason of increase can be explained of martensitic transformation or stress release.Dielectric temperature spectra showed that the degree of dispersion enhanced in tetragonal ferroelectric phase and weakened in rhombohedral ferroelectric phase when ZrO₂ can be seen evidently.更多还原