【作者】 吕振刚；

【导师】 姚琲；

【作者基本信息】 天津大学 ， 材料学， 2007， 博士

【摘要】 本文采用高温固溶法和甘氨酸燃烧合成法制备了Yb₂O₃、Sc₂O₃（Dy₂O₃）、Al₂O₃和CaO复合掺杂YSZ固体电解质材料，对其电性能、烧结性、弯曲强度和微结构等进行了实验分析，并采用密度泛函理论（DFT）方法对多元素复合掺杂ZrO₂改性机理进行了研究。此外，采用分子动力学（MD）方法模拟了AFM Ni针尖与Au基体的相互作用过程。在ZrO₂中添加适量由Y2O3、Yb₂O₃、Sc₂O₃（Dy₂O₃）组成的复合掺杂剂，可以保持ZrO₂高温立方萤石结构、增大晶格常数及氧空位迁移通道半径（R）、改善材料晶界性质、有效提高试样电导率、延缓材料老化速度。添加复合掺杂剂在8⁸.6mol%时，试样电导率得到显著提高（1000℃时达0.19S/cm），且试样在1000℃下连续工作900h，仍具有较高电导率（约0.15S/cm）。继续添加少量Al₂O₃对材料电性能影响较小，添加少量CaO使电导率大幅下降（⁵0%）。DFT计算表明，Y、Yb和Sc在ZrO₂中取代Zr后，阴离子与阳离子间键长产生不均等的变化，使ZrO₂立方结构得以稳定，同时引起ZrO₂晶格畸变、离子电荷发生重新分布，有效调制了电子能带结构中电子轨道的分布和价带与导带的位置，减小了能隙宽度，使材料的导电性提高。差分电荷密度的计算结果表明，多元素掺杂情况下原子间成键差异较大，掺杂阳离子周围产生了电子在局域稀少的电子分布状态。AFM Ni针尖与Au基体相互作用过程的MD模拟表明，Ni针尖与A u（001）表面接近至0.23nm时，受范德瓦尔斯引力的作用，Ni针尖与Au基底发生跳接，体系势能显著降低。Ni针尖继续进针，针尖原子与Au（001）表层原子相互作用，产生纳米压痕，部分Au原子粘着在Ni针尖周围，Au基体表层原子发生位移、原子层错和原子面滑移等现象，体系势能有所升高。随后刚性悬臂被提起，Ni针尖连续向上运动，在Ni针尖与Au基体之间发生部分原子交换的同时，形成了以Au为主体的“细颈”，“细颈”逐渐增长直至断裂，这与金属具有的良好延展性相一致。更多还原

【Abstract】 Yb₂O₃, Sc₂O₃ （Dy₂O₃）, Al₂O₃ and/or CaO doped-YSZ electrolyte materials wereprepared by high-temperature solid-state method and combustion synthesis withglycin, respectively. The material properties, including the conductivity, sintering,bending strength and microstructure, were analyzed experimentally. The mechanismof improving material properties by means of doping multi-elements in ZrO₂ wasstudied by the density functional theory （DFT）. In addition, the molecular dynamic（MD） simulation was applied to study the interaction of AFM Ni tip and Au （001）substrate.Introducing Y2O3, Yb₂O₃ and Sc₂O₃ （Dy₂O₃） in ZrO₂ could build a stable ZrO₂ cubicstructure in room temperature, induce the increase of crystal constants and oxygenvacancy transfer passage radii （R）, and improve the grain boundary condition. Itenhanced the high-temperature conductivity and the aging property of samplesremarkably. The conductivity reached 0.19S/cm at 1000℃with the total additives inthe range of 8⁸.6mol%. The conductivity （1000℃） remained about 0.15S/cm afterworking for 900h. Adding a little amount of Al₂O₃ into the multi-elements doped ZrO₂materials reduced the conductivity slightly, and less CaO could reduce theconductivity to 50%.The results of DFT calculations indicated that the replacement of Zr by Y, Yb andSc in ZrO₂ altered the bond length between the anion and the cation in some extentand the cubic structure of ZrO₂ kept stable, but such replacement led to crystaldistortion and made ionic charge redistributed. Consequently, the position of CB andVB was modulated effectively and the bond gap becomes narrow, the ionicconductivity was improved. The calculation of deformation charge densitydemonstrated that there existed different bonding among the atoms in case of multielementsdoping and there were few electrons in particular areas around doped cation.The MD simulation of AFM Ni tip/Au substrate showed that at certain tip-substratedistances （about 0.23nm）, the tip jumped to contact the Au （001） by the van der waalsforce and the potential energy of the system decreased obviously, and then thenanoindentation formed after Ni tip contacting Au （001）, some Au atoms adhered tothe Ni tip. The atoms layer distortion and slippage were observed on Au （001） substrate surface, and the system potential energy increased gradually. When the Nitip left the substrate, some Ni and Au atoms were exchanged, at the same time, aconnective neck mainly composed of Au formed between the tip and the substrate.The neck continued to increase until fracture occurred, which accorded to the metalgood ductibility.更多还原