氧化铟-稀土氧化物共掺CeO2基导电电解质材料的制备与表征

设计了以氧化铟与稀土氧化物（La2O3或Nd2O3）为共同掺杂元素的新型掺杂技术，并利用以聚乙烯醇为聚合剂的化学合成方法制备了CeO2基氧离子导电电解质材料。X射线衍射分析表明，本实验采用的湿化学合成方法容易获得具有纳米结构的高纯氟化钙型结构的CeO2基导电材料．材料导电性的交流阻抗测试分析说明，适当比例的氧化铟与稀土氧化物共掺能有效提高CeO2的导电性；其导电性比相同合成方法制备的Sm2O3掺杂CeO2的导电性更好。利用有效离子半径和相关结合焓理论分析了不同掺杂氧化物对CeO2基材料离子导电性影响。     

草酸共沉淀法制备Sm掺杂CeO2粉末研究

采用草酸盐共沉淀法制备Sm2O3掺杂CeO2粉末(SDC),XRD分析结果表明为纯相的Sm2O3掺杂CeO2(SDC)固溶体.采用XRD、SEM、TG/DSC、激光粒度分析仪等对粉末的性质和制备工艺条件进行了研究.通过优化沉淀反应pH值,草酸溶液浓度和沉淀物的煅烧温度等制备工艺条件,得到高烧结活性的SDC粉末,沉淀反应pH值为6～7,草酸浓度为0.3mol·L-1形成的草酸沉淀物在700℃煅烧的氧化物粉末,1350℃烧结可以达到95%的理论密度.     

Sm2O3掺杂BaTiO3陶瓷的结构与电性能研究

采用溶胶-凝胶法制备了掺杂不同浓度Sm2O3(分别为0.001,0.002,0.003,0.005,0.007mol)的BaTiO3陶瓷,并对其结构与电性能进行了研究.结果表明:Sm2O3掺杂BaTiO3陶瓷的晶型在室温下为四方相,而且随着Sm2O3掺杂浓度的增加,BaTiO3陶瓷的晶粒尺寸变小,说明Sm2O3掺杂对BaTiO3陶瓷晶粒的生长有一定的抑制作用;Sm2O3掺杂BaTiO3陶瓷的电阻率比纯BaTiO3陶瓷明显下降,当添加量为0.001mol时,电阻率最小,.从4.3×109Ω·m下降为6.536×103Ω·m;Sm2O3掺杂BaTiO3陶瓷的晶粒电阻随着温度的变化,呈现NTC效应,而晶界电阻随着温度的变化,呈现PTC效应,且晶界电阻远远大于晶粒电阻,说明该材料的PTC效应是由晶界效应引起的.     

Sm_2O_3掺杂CeO_2纳米晶的制备及其生长动力学

本研究以Ce(NO3)3.6H2O和Sm2O3为主要原料,采用共沉淀-喷雾干燥法制备出Sm2O3掺杂CeO2(SDC)的纳米粉末。通过对制得粉体进行DSC-TG、XRD、SEM等表征,研究了SDC纳米晶在煅烧过程中的晶体生长动力学。结果表明:400℃以下,煅烧时间对SDC晶粒尺寸的影响很小,随着温度的升高,其影响逐渐增大,800℃时,煅烧时间对晶粒尺寸的影响很大;但随着煅烧温度的提高,其影响又逐渐减小,在1000℃时,晶粒粒径随着煅烧时间的延长,不再发生变化。根据晶体生长动力学方程,SDC的晶体生长机制在不同温度条件下存在一定差异,在低温下(300-400℃),界面反应占主导;中温下(500℃左右),纳米效应、界面反应与扩散传质的共同作用;高温下(600-800℃),体现为扩散传质。     

发光二极管用荧光材料Sr2CeO4:Sm3+的合成及其发光特性

以具有一维结构的Sr2CeO4化合物为研究对象、Sm3 作为发光中心,探索了其作为LED用荧光材料的可能性.用高温固相法于1200℃、6h合成了Sr2CeO4:Sm3 系列单相粉末样品,并研究了其发光性质.结果表明,在365nm激发下,从荧光光谱中可以看出存在从基质向稀土离子的能量转移.通过调节荧光材料Sr2CeO4:Sm3 中稀土离子Sm3 的掺杂浓度,可以调谐发光体的发光颜色,当Sm3 离子浓度较小(<3%)时,体系发出很强的白光;当Sm3 离子浓度较大(3%～15%)时,体系发出红光.测量了荧光材料的色坐标,发现Sr2CeO4:1%Sm3 的色坐标是(0.334,0.320),接近于纯白色(0.33,0.33),可以作为一种新型的UV-LED用单一白色荧光材料.     

Y2O3、Al2O3掺杂对CeO2的烧结及电性能的影响

本文采用溶胶-凝胶法制备了不同含量的Y2O3掺杂的CeO2粉体，并在4mol％Y2O3—CeO2粉体中掺入Al2O3，研究了各样品的烧结性能和电性能。结果表明：适量的掺杂Y2O3能提高氧化铈的密度，但Y2O3含量超过4％mol后密度下降。一定量的Al2O3也能提高材料的烧结密度。随着Y2O3含量的增大，CeO2的电导先增大后减小，而掺入Al2O3对材料的电导不利。     

Sm3+/Ce3+/Tb3+共掺CaO-B2O3-SiO2发光玻璃的制备及发光性能研究

采用高温熔融法制备了Sm3+/Ce3+/Tb3+共掺杂的CaO-B2O3-SiO2发光玻璃材料,并用荧光分光光度计和CIE色度坐标对其发光性能进行了研究。发射光谱表明,在374nm激发下,Sm3+/Ce3+/Tb3+共掺杂CaO-B2O3-SiO2发光玻璃的发射光谱中同时观测到了红橙光、蓝光和绿光的发射带,这些发射带的混合实现了白光发射。此外,在Sm2O3和Tb4O7含量不变的情况下,随着CeO2含量的减小,Sm3+/Ce3+/Tb3+共掺杂发光玻璃的发光颜色在白光区逐渐由蓝光区附近过渡到黄光区附近。     

掺杂镧和铈的TiO2纳米粒子的结构相变

以钛酸四丁酯,La2O3和Ce(NO3)3@6H2O为原料,采用溶胶-凝胶法制备了纯的和分别掺杂5mol%镧和铈的TiO2纳米粒子,并利用XRD,TG-DTA,TEM和XPS等测试技术对样品的晶型、尺寸和形貌等进行了表征,主要考察了镧和铈的掺杂对TiO2的晶粒尺寸和锐钛矿→金红石结构相变的影响,并初步的探讨了镧和铈的作用机理.结果表明,600℃焙烧而获得的TiO2纳米粒子具有与P-25型TiO2粒子相类似的组成、结构、形貌和粒子尺寸;掺杂剂镧和铈分别以La2O3和CeO2小团簇形式存在,并比较均匀的弥散在TiO2纳米粒子中,二者的掺杂抑制了锐钛矿晶粒的增长和锐钛矿→金红石的结构相变,使相变温度显著提高,晶格畸变增大,而镧比铈的作用更加显著.镧和铈的作用机理可能主要与掺杂离子的半径和价态以及稀土氧化物的存在和熔点等有关.     

用喷雾热分解法制备Gd2O3-Y2O3-ZrO2电解质材料的性能

用喷雾热分解方法制备了2 mol%Gd2O3-8YSZ的粉末,用激光粒度分析,X射线衍射(XRD),BET法和扫描电子显微镜(SEM)检测粉末和陶瓷体的性能和结构.结果表明,获得的粉末粒径为12.18 μm,晶粒尺寸为100 nm,比表面积为25.09 m2/g.粉末和陶瓷体材为立方结构.陶瓷体的烧结密度大于98%理论密度.在操作的温度高于600℃下的电导率达2×10-3 S/cm.证实Gd2O3-8USZ材料完全适用于作中温固体氧化物燃料电池(SOFC)的电解质.     

稀土Sm掺杂TiO2第一性原理计算及光催化性能评价

以钛酸四丁酯和六水合硝酸钐为原材料,采用溶胶-凝胶法制备了纯二氧化钛及镧系稀土钐(Sm)掺杂改性TiO2光催化剂。基于密度泛函理论第一性原理,采用分子模拟对纯TiO2及Sm掺杂改性TiO2光催化剂的电子结构进行计算分析,并对样品进行表征。以卤素灯为可见光源,目标污染物为一氧化氮(NO)气体,评价了各样品在可见光条件下对NO气体的光催化活性。结果表明,Sm掺杂改性能调整TiO2晶体的内部电子结构,Sm3+取代Ti 4+形成氧空位及晶格缺陷,引入中间杂质能级,抑制光生电子与空穴的有效复合,降低带隙宽度,提升光催化剂的光响应范围及光催化活性。在稀土Sm掺杂量为0.2%(质量分数),煅烧温度为550℃,光照时间为40min的条件下,Sm掺杂改性TiO2光催化剂对NO的降解率达到81.74%。     

Synthesis and Characterization of SmxGdyCe1-x-yO2-δ Nanopowders

SmxGdyCe1-x-yO2-δ (x+y=0.2 and x=0, 0.04, 0.08, 0.12, 0.16, 0.2) nanopowders were prepared by a coprecipitation method. The zeta potential and sedimentation volume of Ce(OH)4 aqueous dispersions at different pH values were measured. The isoelectric point (IEP) of Ce(OH)4 suspensions is 7.0. The maximum potential value of -18.5 mV and maximum sedimentation volume of 19 ml are reached at pH=10. The evolution behaviors of the xSm(OH)3•yGd(OH)3•(1-x-y)Ce(OH)4 dried powders in the heating process was characterized by DTA/TG and XRD. The powders decompose to ceria based solid solution at a temperature below 300℃ and forms cubic fluorite structure ceria at about 650℃. The properties of SmxGdyCe1-x-yO2-δ solid solutions were characterized by XRD, TEM and BET. The lattice parameter of doped CeO2 increases linearly with increasing Sm3+ substitution (or decreasing Gd3+ substitution). The particle size of the doped ceria powders is from 5 nm to 10 nm     

Effect of submicron grains on ionic conductivity of nanocrystalline doped ceria

Doped ceria has been considered for high oxygen ion conductivity for solid oxide fuel cells. In the present study, 20 mole% samarium doped nano ceria powder was prepared by wet chemical synthesis and sintered at different temperatures to retain submicron grains (> 92-96% density). ionic conductivity of the sintered pellets was measured using impedance spectroscopy as a function of temperature (200-800 degrees C). The total maximum conductivity was 1.0 x 10(-2)S.cm(-1) (at 600 degrees C) for samples sintered at 1200 degrees C. The activation energy at higher test temperature decreases with the decrease in the sintering temperature (by 25%). The grain boundary, grain interior conductivity and activation energy of the electrolyte were correlated to the resulting microstructure. It has been demonstrated that use of doped nano ceria powder as precursor not only reduced the sintering temperature but also provided segregation free grain boundary for engineering higher conductivity dense electrolytes.     

纳米CexGd1-xO2-δ复合氧化物的制备及表征

采用柠檬酸溶胶-凝胶法(Sol-Gel),以Ce(NO_3)_3·6H_2O、Gd_2O_3、柠檬酸为原料,制备纳米级Ce_xGd_(1-x)O_(2-δ)复合氧化物,对制得的样品进行X射线衍射、比表面、扫描电镜及能谱和透射电镜表征,研究样品的组成、晶粒大小、比表面积和样品形貌特征。结果表明,Ce_xGd_(1-x)O_(2-δ)复合氧化物在600℃和800℃焙烧后均形成均匀的面心立方CeO_2基固溶体和/或体心立方Gd_2O_3基固溶体。单组分Gd_2 O_3样品在800℃焙烧后形成具有体心立方的Gd_2O_3物相,经600℃焙烧后还同时含有43%(质量分数)的六方Gd_2O_2CO_3晶型。对于同一Gd~(3+)掺杂比例样品,焙烧温度越高,晶粒越大,比表面积越小;同一焙烧温度样品的晶粒尺寸随Gd~(3+)掺杂量增大先减小后增大,但均小于单组分CeO_2和Gd_2O_3,且Ce_(0.5)Gd_(0.5)O_(2-δ)样品晶粒最小。表明复合氧化物的形成提高了抗烧结能力,形成更多孔隙结构,使样品晶粒变小,比表面积变大,并且x=0.5为形成最小纳米级样品的最佳比例。     

Effect of Sm and Mg co-doping on the properties of ceria-based electrolyte materials for IT-SOFCs

Samples of Sm and Mg co-doped ceria electrolytes of Ce_0.8Sm_0.2−xMg_xO_2−δ (x = 0, 0.05, 0.10, 0.15 and 0.20) were sintered from powders obtained by solid-state reaction method. The structures and electrical properties were characterized by X-ray diffraction (XRD) and AC impedance spectroscopy (IS). The thermal expansion curves of samples were measured and the thermal expansion coefficients between 100 and 800 °C were calculated. Results showed that co-doping with appropriate ratio of Sm and Mg can improve the electrical performance of ceria-based electrolytes. As the substitution amount of Mg for Sm increased up to 50 mol%, the conductivity of the samples maintained almost unchanged or even slightly higher than that doped only with Sm in intermediate temperature. The results suggest that the materials cost for producing the ceria-based intermediate temperature solid oxide fuel cells (IT-SOFCs) may be significantly reduced owing to the cost difference between Mg and Sm.     

钆锆烧绿石粉体的高温固相制备工艺

为获得钆锆烧绿石(Gd2Zr2O7)粉体的制备工艺条件,以Gd2O3和ZrO2粉体为原料,在温度为1 300～1 500℃的条件下,采用高温固相法制备钆锆烧绿石粉体;采用X射线衍射法对所制备的样品进行物相与结构分析,用扫描电子显微镜观察样品的微观形貌。结果表明,在常压、保温72 h的条件下,钆锆烧绿石的最佳煅烧温度为1 500℃,此时所制备的晶体结晶程度高,晶粒尺寸在3μm左右。     

Effect of grain size on the electrical properties of samaria-doped ceria solid electrolyte

Samaria-doped ceria (SDC) ceramic nanopowders have been synthesized by three different methods: co-precipitation, combustion, and hydrothermal. The Ce0.8Sm0.2O1.9 nanopowder with an average aggregate size of 47 nm and crystallite size of 7-11 nm prepared by the hydrothermal method has been used for further consolidation by pressureless (PLS) and spark plasma (SPS) consolidation methods at 1000-1400 degrees C to obtain dense ceramic samples with different grain sizes in the wide range of 80 to 1500 nm. The total electrical conductivities of 0.010-0.015 S/cm at 600 degrees C were obtained for the PLS-derived samples. The dense SDC nanostructured ceramics consolidated by SPS showed the very low activation energy of only 0.66 eV at temperatures of 300-400 degrees C, and the total electrical conductivity of 0.0056 S/cm. The enhancement of the grain-boundary framework quality by annealing of the nano-SDC electrolyte at 1000 degrees C for 20 hours almost doubled the average grain size. In addition the electrical conductivity was enhanced almost 40%, while keeping the activation energy unchanged.     

RETRACTED ARTICLE: Determination of dopant of ceria system by density functional theory

Oxides with the cubic fluorite structure, e.g., ceria (CeO₂), are known to be good solid electrolytes when they are doped with cations of lower valence than the host cations. The high ionic conductivity of doped ceria makes it an attractive electrolyte for solid oxide fuel cells, whose prospects as an environmentally friendly power source are very promising. In these electrolytes, the current is carried by oxygen ions that are transported by oxygen vacancies, present to compensate for the lower charge of the dopant cations. Ionic conductivity in ceria is closely related to oxygen-vacancy formation and migration properties. A clear physical picture of the connection between the choice of a dopant and the improvement of ionic conductivity in ceria is still lacking. Here we present quantum-mechanical first-principles study of the influence of different trivalent impurities on these properties. Our results reveal a remarkable correspondence between vacancy properties at the atomic level and the macroscopic ionic conductivity. The key parameters comprise migration barriers for bulk diffusion and vacancy–dopant interactions, represented by association (binding) energies of vacancy–dopant clusters. The interactions can be divided into repulsive elastic and attractive electronic parts. In the optimal electrolyte, these parts should balance. This finding offers a simple and clear way to narrow the search for superior dopants and combinations of dopants. The ideal dopant should have an effective atomic number between 61 (Pm) and 62 (Sm), and we elaborate that combinations of Nd/Sm and Pr/Gd show enhanced ionic conductivity, as compared with that for each element separately. An erratum to this article can be found at     

顺电态下掺铝钛酸锶钡陶瓷微结构和介电调谐性能

用传统的电子陶瓷工艺合成Ba_0.6Sr_0.4TiO₃(BST),研究Al₂O₃掺杂对钛酸锶钡陶瓷微结构、介电及调谐性能的影响.通过XRD及SEM的研究表明,Al³⁺能够完全的进入到Ba_0.6Sr_0.4TiO₃晶格内部形成固溶体,同时陶瓷的结晶程度变好,颗粒大而均匀.陶瓷的介电损耗明显减小,介电常数有所降低,调谐率明显上升,其中,掺杂量为0.8wt％Al₂O₃时,陶瓷样品具有最佳的介电调谐性能.     

Mn、Sb掺杂NBT—KBT—BT无铅压电陶瓷的研究

采用传统陶瓷制备工艺,利用XRD、SEM等测试分析方法,研究了MnCO3、Sb2O3掺杂对压电陶瓷晶体结构、表面形貌以及性能的影响。研究结果表明：所有组成均呈单一钙钛矿型固溶体特征,无其它晶相生成。掺杂陶瓷在1160℃左右烧结比较合适。MnCO3表现为典型的“受主”添加物特征。Sb2O3的掺杂对陶瓷性能的影响受多种因素共同作用,当Sb2O3的掺杂量为0.1％（质量分数）时,d33=148pC／N、tanδ=4.2％、εr=1516。MnCO3的掺杂可以促进晶粒生长,Sb2O3的掺杂使晶粒尺寸的均匀性降低。     

Nonlinear Electrical Properties of SnO_2-Li_2O-Nb_2O_5 Varistor System

The electrical properties of (Nb, Li)-doped SnO2 ceramics as a new varistor material were investigated. The sample 97.95%SnO2·0.50%Li2O·0.05%Nb2O5 (mol fraction) sintered at 1450= possess the highest density (ρ=6.77 g/cm3) and nonlinear electrical coefficient (α=11.6). The substitution of Sn4+ with Li+ increases the concentration of oxygen vacancies, together with the formation of solid solution, which will increase the sintering rate greatly and decrease the optimized sintering temperature. The substitution of Sn4+ with Li+ and the variation of temperature play very important effects on the densities, dielectric constant, nonlinear electrical properties and other characteristics of the samples. The properties of the grain boundary barrier and the microstructural characteristics were investigated to ensure the effect of the dopants and the temperature. A grain boundary defect barrier model was used to illustrate the grain boundary barriers formation in SnO2-Li2O-Nb2O5 varistors.