共沉淀法制备Bi3.25La0.75Ti3O12纳米粉体

用硝酸铋、硝酸镧和钛酸四丁酯为原料，硝酸、无水乙醇和去离子水为溶剂，氨水为沉淀剂，采用共沉淀法合成了单相铋层状钙钛矿结构Bi3.25La0．75Ti3O12(BLT)纳米粉体。用DTA／TG和XRD研究了BLT前驱体的热行为和晶相转化过程，用场致发射扫描电子显微镜观察了BLT粉体的颗粒形貌和大小的变化。结果表明：共沉淀前驱体溶液的配制过程中，硝酸铋水解生成的硝酸氧铋不利于层状钙钛矿结构BLT相的合成。利用浓度较高的硝酸作溶剂，可以防止硝酸铋的水解，采用氨基共沉淀法直接合成出了单一相的BLT纳米粉体，在煅烧过程中，未出现Bi2Ti2O3焦绿石相。700℃煅烧2h合成的BLT粉体颗粒不大于100nm，颗粒间结合疏松，具有良好的分散性。     

液态源雾化化学沉积法制备(Pb,La)TiO3薄膜

研究了在Pt/Ti/SiO2 /Si基片上用液态源雾化化学沉积法制备镧钛酸铅 [(Pb ,La)TiO3,PLT]薄膜的工艺 ,并分析了各种因素对其相结构的影响。采用金属有机物热分解工艺的先体溶液 ,在沉积阶段 ,用超声波将先体溶液雾化 ,产生微米级的汽雾 ,由载气 (Ar)引入沉积室进行沉积 ,并在沉积室进行预热处理。重复上述过程 ,直到膜厚达到要求 ,再进行退火处理得到均匀、致密的薄膜。此工艺各项参数如下 :沉积前沉积室内气压为 4× 10 - 3Pa ;沉积时沉积室内气压为 8× 10 3～ 9× 10 3Pa ,沉积时基片温度为 2 0～ 2 5℃ ;预处理温度为 30 0℃ ;最佳热处理温度为 60 0℃ ;超声雾化器工作频率为 1.7MHz;薄膜沉积速率为 3nm/min。XRD和SEM图分析说明 ,制备的铁电薄膜具有钙钛矿结构     

Dependence of the Microstructure and the Electrical Properties of Lanthanum-Substituted (Na1/2Bi1/2)TiO3 on Cation Vacancies

The sintering and electrical characteristics of La-modified Na_1/2Bi_1/2TiO₃ (NBT) was investigated from a defect structure viewpoint. To reveal the role of cation vacancies, two series of ceramics, with different cation vacancies, were processed to compensate the excess positive charge of lanthanum ions. In a region of complete solid solution, the grain size of NBLT-B {[(Na_0.5Bi_0.5)_{1− x} La _x ]Ti_{1−0.25 x} O₃} was smaller than that of NBLT-A {[(Na_0.5Bi_0.5)_{1−1.5 x} La _x ]TiO₃} and densification was enhanced more effectively in NBLT-B. With the aid of thermoelectric power, electric conductivity, and electrotransport measurements, it was found that different sintering behaviors between NBLT-A and NBLT-B specimens were related to the change in the type of cation vacancies present and that lanthanum ion–cation vacancy pairs played an important role in reducing the grain growth and enhancing the densification process.     

Preparation of V doped lanthanum silicate electrolyte ceramics by combustion method and study on conductance mechanism

Vanadium doped La_9.33Si_6−xV_xO_26+0.5x (x = 0.5, 1.0, 1.5) (LSVO) electrolyte powder was prepared by combustion method at 600°C for 5-7 min. The powder was sintered at 1500°C for 3 hours to prepare LSVO ceramics. XPS, IR, XRD, and EIS analysis show that V⁵⁺ doping replaces Si⁴⁺ in [SiO₄] to form [Si(V)O₄] tetrahedron. With the increase in x, the lattice volume increase. When x = 2.0, the LaVO₄ phase was formed, indicating that the limit doping amount of V⁵⁺ replacing Si⁴⁺ is x ≤ 1.5. The conductivity of LSVO increases significantly with the increase in x (x ≤ 1.0), which attributed to the defect reaction caused by V⁵⁺ doping. The addition of the interstitial oxygen Oi* in 6₃ channels and the increase of lattice volume leads to increased conductivity. When x = 1.0, the highest conductivity is 1.46 × 10⁻² S·cm⁻¹ (800°C). The doping enhancement conductivity mechanism is the Interstitial oxygen defect-Lattice volume composite enhancement mechanism.     

镧对WO3/ZrO2固体超强酸酸强度和结构的影响

通过共沉淀法制备了合适酸强度,比表面积为175.284 3 m2.g-1,最可几孔径在5.99 nm,负载镧的WO3/ZrO2固体超强酸催化剂。用Hammett指示剂法、XRD、N2等温吸附/脱附、DTA等方法考察了负载稀土镧后对催化剂的酸强度、比表面积、孔结构和热稳定性的影响。结果发现：La能均匀掺入WO3/ZrO2固体超强酸中,且适当加入稀土元素镧不但可以提高其酸强度,而且可以稳定结构、增加比表面积。     

溶胶-凝胶法制备掺镧钛酸钡薄膜及其光学性质研究

以硝酸镧、醋酸钡、钛酸四丁酯为原料,采用溶胶一凝胶旋涂法制备掺La的钛酸钡薄膜,研究薄膜的晶体结构、表面形貌、紫外-可见光吸收性能及光学带隙。研究结果表明,纯钛酸钡和掺La钛酸钡薄膜均为单一四方钙钛矿结构,La3＋的引入可以使钛酸钡薄膜在可见光区的透过率和光学带隙有一定程度下降,而退火温度对掺镧钛酸钡薄膜光学带隙基本无...     

镧对大鼠回避学习能力的影响

为了探讨氯化镧(LaCl3)染毒对子代大鼠回避学习记忆能力的影响。采用健康成年雌性Wistar大鼠24只,随机分为对照组(饮用蒸馏水);低剂量染镧组(饮用含0.25%LaCl3的蒸馏水溶液)、中剂量染镧组(饮用含0.5%LaCl3的蒸馏水溶液)和高剂量染镧组(饮用含1.0%LaCl3的蒸馏水溶液),每组6只动物。自雌鼠受孕日至仔鼠断乳后1个月以自由饮水的方式摄入镧。通过穿梭箱实验判断仔鼠的主被动逃避学习能力。结果显示,中剂量组仔鼠主动逃避潜伏期和电击次数显著高于低剂量组和对照组(P0.05),电击时间显著高于对照组(P0.05);高剂量组仔鼠主动逃避潜伏时间、电击次数和电击时间均显著高于中剂量组、低剂量组和对照组(P0.05)。LaCl3染毒造成大鼠主动逃避能力下降,LaCl3染毒组仔鼠表现出剂量依赖的回避学习能力损伤(P0.05)。     

钒对USY型分子筛的影响及氧化镧在钒捕集中的作用

模拟催化裂化高温水热再生环境,采用X射线衍射、N₂物理吸附、高分辨电子透射显微镜与NH₃-程序升温热脱附等方法,研究了重金属元素钒(V)对催化剂活性组分水热超稳Y型分子筛(USY型分子筛)的破坏行为;在此基础上,研究了稀土氧化物氧化镧(La₂O₃)对重金属V的捕集作用。结果表明：当分子筛负载较高质量分数的V时,分子筛的晶体结构遭到严重破坏;与未负载V的催化剂相比,负载质量分数为0.5%的催化剂,转化率降低了16.3个百分点,目标产物(液化气和汽油)收率显著降低,副产物干气、焦炭收率大幅增加;向模型催化剂中添加La₂O₃可以提高催化剂的重金属V捕集能力,在V负载质量分数为0.6%的情况下,含有La₂O₃的模型催化剂的原料油转化率和目标产物收率大幅增加。     

Hydrothermal microwave-assisted synthesis of LaFeO3 catalyst for N2O decomposition

Lanthanum orthoferrite powders were synthesized via one-step hydrothermal reactions under mild conditions using microwave and conventional heating. The use of microwave irradiation during the synthesis allows one to obtain nanocrystalline LaFeO₃ with a higher yield and reduced crystallite and particle size within a 16 times shorter duration (3 hours) at a lower temperature of 220°C as compared to the conventional heating. The catalytic decomposition of nitrous oxide was performed over both samples, it was shown that the sample obtained under microwave conditions demonstrates enhanced activity as a catalyst: N₂O decomposes completely at 700°C over the catalyst formed at microwave conditions, while the comparative catalyst prepared by conventional heating reaches a lower conversion of only 60% at the same temperature and catalytic reaction conditions.     

Low-temperature phase formation in the SrF2–LaF3 system

Phase formation in the SrF₂–LaF₃ system was studied at temperatures ranging from 300°C to 450°C using nitrate flux. The solubility of LaF₃ in SrF₂ decreases with decreasing temperature. The equilibrium width of the solid solution region Sr_1−xLa_xF_2+x at 400°C, it is 44.6 ± 0.4 mol% LaF₃ (x = 0.446), at 350°C — 38.3 ± 0.7 mol% LaF₃ (x = 0.383), and decreases almost to zero at 300°C.