低温热处理氧化钨电致变色薄膜的制备与性质

低温热处理氧化钨电致变色薄膜的制备与性质;电致变色;溶胶 凝胶法;聚乙烯醇;氧化钨     

合成方法对BICUVOX.10膜在中低温条件下透氧性能的影响

BICUVOX.10(Bi2V0.9Cu0.1O5.35)粉体和膜片采用固态反应法(SSR)和EDTA-柠檬酸联合络合法(EC)制备,并使用X射线衍射、扫描电镜、氧气渗透测试和电化学阻抗谱方法对材料的件能进行了对比表征和测试.XRD和SEM结果表明,采用EC法更容易制备纯相的BICUVOX.10粉体,但是膜片的稳定性较SSR法制备的差.在不引起电压波动的前提下,采用SSR方法和EC方法制备的膜片上能加载的最大电流分别为1.6和1.2A/cm2,对应的400℃条件下透氧量分别为4.5和3.9ml/(min cm2).膜片的微结构如粒径等对透氧性能和电导性能影响很大.     

Samarium Based High Surface Area Perovskite Type Oxides SmFe1-XAlXO3 (X=0.00, 0.50, 0.95).Part I, Synthesis and Characterization of Materials

High specific surface area (ssa) perovskite type solids based on samarium (SmFe_1-xAl_xO₃, x = 0.00, 0.50, 0.95) were prepared using hexadecyltrimethyl-ammonium bromide C16TAB as a precursor and gelating agent. The structure of perovskite is fully developed at 600oC for the SmFeO3 solid but not for the other materials. The ssa of the solids varies (33.5 m²g^-1 - 1 m²g^-1) depending on composition and calcination temperature.     

Synthesis and Crystal Structure of α‐ThTe3

The binary thorium tritelluride, α‐ThTe₃, was synthesized by solid‐state methods at 1223 K. From a single‐crystal X‐ray diffraction study the material crystallizes in the TiS₃ structure type with two formula units in space group C²_2h–P2₁/m of the monoclinic system in a cell with lattice constants a = 6.1730 (4) Å, b = 4.3625(3) Å, c = 10.4161(6) Å, and β = 97.756(3)° (at 100 K). The asymmetric unit of this compound comprises one Th atom and three Te atoms each with site symmetry m. Each Th atom is coordinated to eight Te atoms in a bicapped trigonal‐pyramidal arrangement. Th–Te distances range from 3.1708(4) Å to 3.2496(6) Å. The structure features a Te–Te interaction 2.7631(8) Å in length, which is typical for a Te–Te single bond. Thus α‐ThTe₃ may be charge balanced and formulated as Th⁴⁺Te^2–Te₂^2–.     

Optimizing the Atomic Layer Deposition of Alumina on Perovskite Nanocrystal Films by Using O2 As a Molecular Probe

Encapsulation methods have shown to be effective in imparting improved stability to metal-halide perovskite nanocrystals (NCs). Atomic layer deposition (ALD) of metal oxides is one of the promising approaches for such encapsulation, yet better control on the process parameters are required to achieve viable lifetimes for several optoelectronic and photocatalytic applications. Herein, we optimize the ALD process of amorphous aluminum oxide (AlO_x) as an encapsulating layer for CsPbBr₃ NC thin films by using oxygen (O₂) as a molecular diffusion probe to assess the uniformity of the deposited AlO_x layer. When O₂ reaches the NC surface, it extracts the photogenerated electrons, thus quenching the PL of the CsPbBr₃ NCs. As the quality of the ALD layer improves, less quenching is expected. We compare three different ALD deposition modes. We find that the low temperature/high temperature and the exposure modes improve the quality of the alumina as a gas barrier when compared with the low temperature mode. We attribute this result to a better diffusion of the ALD precursor throughout the NC film. We propose the low temperature/high temperature as the most suitable mode for future implementation of multilayered coatings.     

PbO-PbI2复合物膜转化的CH3NH3PbI3钙钛矿薄膜及其光电特性

有机-无机卤化物钙钛矿是一类优异的光电材料. 在过去四年内, 基于有机-无机卤化物钙钛矿的光电器件实现了超过15%的光电转换效率. 而有机-无机卤化物钙钛矿材料的可控制备是保证其在光电器件中应用的基础. 本文采用新的沉积方法在玻璃衬底表面制备了一种典型的有机-无机卤化物钙钛矿CH₃NH₃PbI₃薄膜. 其制备过程是: 采用超声辅助的连续离子吸附与反应法在玻璃衬底表面沉积PbO-PbI₂复合物膜, 之后与CH3NH3I蒸汽在110 ℃环境下反应, 将PbO-PbI₂复合物膜转化成CH₃NH₃PbI₃钙钛矿薄膜. 对CH₃NH₃PbI₃薄膜的微观结构, 结晶性及其光电性能等进行了表征. 结果表明, CH₃NH₃PbI₃薄膜呈晶态, 具有典型的钙钛矿晶体结构. 薄膜表面形貌均匀, 晶粒尺寸超过400 nm. 在可见光范围, CH₃NH₃PbI₃薄膜透过率低于10%, 能带宽度为1.58eV. 电学性能研究表明CH₃NH₃PbI₃薄膜表面电阻率高达1000 MΩ. 高表面电阻率表明CH₃NH₃PbI₃薄膜具有一定的介电性能, 其介电常数(ε_r)在100 Hz时达到155. 本研究提出了一种制备高质量CH₃NH₃PbI₃钙钛矿薄膜的新方法, 所得CH₃NH₃PbI₃薄膜可望在光、电及光电器件中得到应用.     

Synthesis and high-temperature thermoelectric properties of Ni and Ti substituted LaCoO3

The effect of Ti and Ni substitution in LaCoO_3−δ was investigated by means of electrical resistivity and Seebeck coefficient properties in a broad temperature range. The studied compounds crystallize in a rhombohedral crystal structure within the whole substitution range. The Seebeck coefficient of most of the studied compounds is positive indicating predominant hole-type charge carriers. The electrical resistivity decreases with increasing temperature for all compositions. Increasing the Ni content results in a decrease of the electrical resistivity, while the resistivity increases with increasing Ti content. The power factor, PF, for the Ni substituted samples is PF=1.42×10⁻⁴ W/m² K for x=0.10 at and decreases with temperature. The LaCo_1−xTi_xO_3±δ compounds reveal an enhancement of the power factor with increasing temperature. Ti substitution leads to a higher power factor compared to that of Ni substitution at .     

Polymer Zwitterions for Stabilization of CsPbBr3 Perovskite Nanoparticles and Nanocomposite Films

Functional polymers with sulfobetaine or phosphorylcholine zwitterions as pendent groups are demonstrated as both ligands and host matrices for CsPbBr₃ perovskite nanoparticles (PNPs). These polymers produce nanocomposite films with excellent NP dispersion, optical transparency, and impressive resistance to NP degradation upon exposure to water. Multidentate interactions of the zwitterion‐containing copolymers with the PNPs induce dispersed or weakly aggregated nanocomposite morphologies, depending on the extent of zwitterionic functionality in the polymer. Incorporating additional functionality into the polymers, such as benzophenone pendent groups, yields lithographically patternable films, while time‐resolved photoluminescence measurements provide insight into the electronic impact of PNPs in zwitterionic polymer matrices.     

基于易升华添加剂辅助合成纯相富铯(CH(NH2)2)xCs1−xPbI3 钙钛矿

钙钛矿材料化学组分是决定钙钛矿太阳能电池效率和稳定性的关键,纯无机钙钛矿CsPbI₃具有相对较好的热稳定性和光稳定性,但由于Cs⁺具有较小的离子半径而导致无机钙钛矿相不稳定。最近研究发现富铯FA_xCs_1?xPbI₃钙钛矿具有相对稳定的相结构,且可以很大程度上保持无机钙钛矿材料的热稳定性和光照稳定性,是一种非常具有前景的钙钛矿材料体系。目前这种富铯的FA_xCs_1?xPbI₃材料合成是通过引入过量有机组分FAI实现的,其中FAI一方面充当钙钛矿的掺杂剂,另一方面过量的FAI充当添加剂。由于其具有较高的升华温度,后续需要较高的温度使过量的FAI升华,实际上这在实验上很难实现对FAI升华量的精确控制。本文重点研究具有低升华温度的胺类,如碘甲胺(MAI)、碘化二甲胺(DMAI)、碘化乙胺(EAI)、碘化胺(NH₄I)和醋酸甲脒(FAAC),作为添加剂制备富铯FA_xCs_1?xPbI₃钙钛矿材料体系的可行性,这一方面可以有效降低钙钛矿薄膜的热处理温度;另一方面可拓宽的制备纯相钙钛矿成分的窗口期,这对大面积制备纯相富铯FA_xCs_1?xPbI₃钙钛矿薄膜尤为重要。结果表明MAI和DMAI可以作为合成FA_xCs_1?xPbI₃钙钛矿材料的有效添加剂,其与PbI2间较强的作用力可以促进Cs₄PbI₆的形成并有效抑制δ-CsPbI₃副产物的生成。合适的升华温度可以使薄膜在保持钙钛矿相结构的同时在较低温度升华去除过量的添加剂,最终实现在相对温和的条件下制备纯相富铯FA_xCs_1?xPbI₃钙钛矿材料。     

Hydrothermal Synthesis and Characterization of Perovskite Oxide AgTaO3

The perovskite-type AgTaO₃ crystals were prepared by mild hydrothermal method and determined by powder X-ray diffraction. Rietveld refinement indicates that AgTaO₃ crystallized in an orthorhombic system with the space group Pcmn. The lattice parameters are a=5.5822(1) nm, b=7.8522(2) nm and c=5.5347(1) nm, with α=β=γ= 90.0o. The compound was characterized by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy(HR-TEM) and UV-Vis diffuse reflectance spectrometry (UV-Vis DRS). The photocatalytic activity of AgTaO₃ powder was evaluated by the degradation of Congo red under UV-light irradiation. The result shows that the titled compound has a high photocatalytic activity at room temperature and potential application in photocatalysis.     

Perovskites as Precursors for Ni/La2O3 Catalysts in the Dry Reforming of Methane: Synthesis by Constant pH Co‐Precipitation,Reduction Mechanism and Effect of Ru‐Doping

LaNiO₃ perovskite is an interesting precursor for Ni/La₂O₃ catalysts for the dry reforming of methane at high temperatures. Precursors have been synthesized by co‐precipitation without, with 2.5 at %, and with 5 at % Ru doping. The presence of Ru leads to a stabilization of the perovskite structure and hinders the decomposition into NiO and Ruddlesden‐Popper mixed oxides La_n+1Ni_nO_3n+1, which was observed for the Ru‐free sample upon calcination at 1000 °C (n = 3). Upon reduction in hydrogen, a mechanism involving at least two steps was observed and the first major step was identified as the partial reduction of the precursor leading to a LaNiO_2.5‐like intermediate. The second major step is the reduction to Ni metal supported on La₂O₃ independent of the Ru content of the catalyst. In the presence of Ru, indications for Ni‐Ru alloy formation and for a higher dispersion of the metallic phase were found. The catalytic activity in DRM of the catalyst containing 2.5 % Ru was superior to the catalysts with more or without Ru. Furthermore, the propensity of coke formation was reduced by the presence of Ru.     

Thermodynamic properties of BaCeO3 and BaZrO3 at low temperatures

Specific heat capacities (C_p) of polycrystalline samples of BaCeO₃ and BaZrO₃ have been measured from about 1.6 K up to room temperature by means of adiabatic calorimetry. We provide corrected experimental data for the heat capacity of BaCeO₃ in the range T < 10 K and, for the first time, contribute experimental data below 53 K for BaZrO₃. Applying Debye's T³-law for T → 0 K, thermodynamic functions as molar entropy and enthalpy are derived by integration. We obtain C_p = 114.8 (±1.0) J mol⁻¹ K⁻¹, S° = 145.8 (±0.7) J mol⁻¹ K⁻¹ for BaCeO₃ and C_p = 107.0 (±1.0) J mol⁻¹ K⁻¹, S° = 125.5 (±0.6) J mol⁻¹ K⁻¹ for BaZrO₃ at 298.15 K. These results are in overall agreement with previously reported studies but slightly deviating, in both cases. Evaluations of C_p(T) yield Debye temperatures and identify deviations from the simple Debye-theory due to extra vibrational modes as well as anharmonicity. The anharmonicity turns out to be more pronounced at elevated temperatures for BaCeO₃. The characteristic Debye temperatures determined at T = 0 K are Θ₀ = 365 (±6) K for BaCeO₃ and Θ₀ = 402 (±9) K for BaZrO₃.     

钙钛矿型CaSiO_3解压缩和重压缩过程的分子动力学模拟

用分子动力学模拟方法 (MD)研究了 3 0 0K时钙钛矿型CaSiO3 ,从高压到负压的解压缩过程 .MD模拟获得的P V关系与实验数据相近 ,与已报道的MD模拟数据基本一致 ,所得体积模量也在实验数据分布范围内 .减压缩和重压缩的MD模拟数据与实验结果相似 .钙钛矿型CaSiO3 解压缩成非晶态时 ,存在两个结构破坏阶段 :破坏硅氧八面体和破坏钙氧二十面体 .当钙氧二十面体被破坏后 ,重压缩不能得到钙钛矿型结构 .只要钙氧二十面体未被破坏 ,重压缩可恢复钙钛矿型结构 .本研究得到的结果尚未见相关报道 .由MD模拟数据计算了CaSiO3 系统的红外光谱 ,分析这些数据可知钙钛矿型CaSiO3 解压缩非晶化是一个二阶软模相变 .研究表明钙钛矿型CaSiO3 结构存在一个等容的亚稳极限 ,其解压缩非晶化是一个受动力学控制的亚稳状态 .     

钙钛矿型CaSiO_3解压缩和重压缩过程的分子动力学模拟

用分子动力学模拟方法（MD）研究了300 K时钙钛矿型CaSiO_3，从高压到负压 的解压缩过程。MD模拟获得的P-V关系与实验数据相近，与已报道的MD模拟数据基 本一致，所得体积模量也在实验数据分布范围内。减压缩和重压缩的MD模拟数据与 实验结果相似。钙钛矿型CaSiO_3解压缩成非晶态时，存在两个结构破坏阶段：破 坏硅氧八面体和破坏钙氧二十面体。当钙氧二十面体被破坏后，重压缩不能得到钙 钛矿型结构。只要钙氧二十面体未被破坏，重压缩可恢复钙钛矿型结构。本研究得 到的结果尚未见相关报道。由MD模拟数据计算了CaSiO_3系统的红外光谱，分析这 些数据可知钙钛矿型CaSiO_3解压缩非晶化是一个二阶软模相变。研究表明钙钛矿 型CaSiO_3结构存在一个等容的亚稳极限，其解压缩非晶化是一个受动力学控制的 亚稳状态。     

Displacive Phase Transitions in and Strain Analysis of Fe-Doped CaTiO3 Perovskites at High Temperatures by Neutron Diffraction

The influence of small amounts of Fe³⁺ on the phase transitions of CaTiO₃ perovskite has been studied by means of in situ high-temperature neutron diffraction. The same sequence of phase transitions as observed in CaTiO₃ is shown by both CaTi_0.9Fe_0.1O_2.95 and CaTi_0.8Fe_0.2O_2.90 perovskites: from orthorhombic Pnma symmetry at room temperature (RT) to cubic Pm3m at high temperature, with an intermediate I4/mcm tetragonal phase which exists over a temperature range of about 100°C. The two phase boundaries in the temperature vs composition phase diagram of the system CaFe_xTi_1−xO_3−x/2 (0≤x≤0.4) decrease in a quasi-linear manner with increasing Fe content up to x=0.2 and then they both drop abruptly to RT. The existence of a second orthorhombic phase (Cmcm), which has been postulated for CaTiO₃, is ruled out in the Fe-doped CaTiO₃ perovskites in view of the behavior of specific diffraction peaks. Strain analysis shows first-order thermodynamic character for the Pnma→I4/mcm transition, while the character of the Pm3m→I4/mcm transition could be second order or tricritical. Shear strains behave more or less classically, as described by order parameter coupling and shear strain/order parameter coupling models. The volume strain has an anomalous coupling with the order parameter components, which appears to be temperature-dependent.     

Synthesis,Characterization and Thermal Behavior of Complexes of Cu(II), Zn(II) and Cd(II) with S,S′-Methylenebis(Cysteine)

Synthesis and characterization, including data on thermal decomposition, are reported for the complexes of S,S'-methylenebis(cysteine) (djenkolic acid) with copper(II), zinc(II) and cadmium(II): CuC₇H₁₂N₂O₄S₂ [I]; ZnC₇H₁₂N₂O₄S₂ [II] and CdC₇H₁₂N₂O₄S₂ [III]. X-ray diffraction showed that the compounds are isostructural and belong to a monoclinic system. According to IR spectra, COO, NH₂ groups and bridging sulfur atoms are the main coordination sites.     

Preparation of La0.75Sr0.25MnO3 Nano-Phase Powders and Films from Alkoxide Precursors

The first purely alkoxide-based sol-gel route to nano-phase powders and thin films of perovskite La_0.75Sr_0.25MnO₃ is described. The phase and microstructure evolution on heat treatment of free gel films to form the target nano-phase oxide were investigated by TGA, IR spectroscopy, powder XRD, SEM and TEM-EDS. The xerogel consisted of a hydrated oxo-carbonate, without remaining alkoxo groups or solvent. Heating at 5°C·min^–1 decomposed the carbonate groups and yielded the pure perovskite La_0.75Sr_0.25MnO₃ at 760°C. The cell dimensions were virtually unchanged from the first observation of perovskite at 680°C, to 1000°C, 4 h. The monoclinic cell of La_0.75Sr_0.25MnO₃ obtained at 1000°C, 4 h, had the dimensions a = 5.475(1), b = 5.504(2), c = 7.771(1) Å, = 90.50(2), fitting the literature data quite well. Crack-free, homogenous, 150 nm thick La_0.75Sr_0.25MnO₃ films were prepared by spin-coating Si/SiO₂/TiO₂/Pt and polycrystalline -Al₂O₃ substrates with a 0.6 M alkoxide solution, followed by heating at 5°C·min^–1 to 800°C, 30 min.     

Synthesis of L-Lysine and L-Glutamic Acid Derivatives with Long Alkyl Chains and Polycondensation of Langmuir-Blodgett Films

Two esters of L-lysine and L-glutamic acid containing long alkyl groups were synthesized and their polycondensation in monolayers and multilayers was investigated. The pressure-area isotherms of the ester of L-lysine depend markedly on the time of residence at the air-water interface. The change of FT-IR spectra of the deposited film, which can be lifted as a Z-type film, indicates that polycondensation can occur in the monolayer at 10°C without any treatment. The spectrum of the film cast from chloroform hardly changed with time. These results lead to the conclusion that a regular arrangement of monomer molecules in the monolayer, where the amino and ester carbonyl groups are concentrated, is more suitable for the polycondensation. The ester of L-glutamic acid can also form stable monolayers which can be easily deposited on a hydrophobic plate as a Y-type film by the Blodgett technique. The polycondensation of multilayers under an atmosphere of triethylamine was investigated by IR spectroscopy. It indicates that the condensation in multilayers proceeds via intermolecular and intramolecular reactions, by which poly(L-glutamate) derivatives and 2-pyrrolidone derivatives are formed, respectively. The condensation in the bulk crystalline powder gives exclusively the 2-pyrrolidone derivative by intramolecular reaction. These results suggest that the monomer molecules in the multilayers are favorably aligned for the intermolecular reaction, in contrast to the situation in the bulk crystalline powder.     

Facile Synthesis of Hierarchical Nanosized Single-Crystal Aluminophosphate Molecular Sieves from Highly Homogeneous and Concentrated Precursors

The synthesis of hierarchical nanosized zeolite materials without growth modifiers and mesoporogens remains a substantial challenge. Herein, we report a general synthetic approach to produce hierarchical nanosized single-crystal aluminophosphate molecular sieves by preparing highly homogeneous and concentrated precursors and heating at elevated temperatures. Accordingly, aluminophosphate zeotypes of LTA (8-rings), AEL (10-rings), AFI (12-rings), and -CLO (20-rings) topologies, ranging from small to extra-large pores, were synthesized. These materials show exceptional properties, including small crystallites (30–150 nm), good monodispersity, abundant mesopores, and excellent thermal stability. A time-dependent study revealed a non-classical crystallization pathway by particle attachment. This work opens a new avenue for the development of hierarchical nanosized zeolite materials and understanding their crystallization mechanism.     

Colloidal Synthesis and Characterization of Molybdenum Chalcogenide Quantum Dots Using a Two-Source Precursor Pathway for Photovoltaic Applications

The drawbacks of utilizing nonrenewable energy have quickened innovative work on practical sustainable power sources (photovoltaics) because of their provision of a better-preserved decent environment which is free from natural contamination and commotion. Herein, the synthesis, characterization, and application of Mo chalcogenide nanoparticles (NP) as alternative sources in the absorber layer of QDSSCs is discussed. The successful synthesis of the NP was confirmed as the results from the diffractive peaks obtained from XRD which were positive and agreed in comparison with the standard. The diffractive peaks were shown in the planes (100), (002), (100), and (105) for the MoS₂ nanoparticles; (002), (100), (103), and (110) for the MoSe₂ nanoparticles; and (0002), (0004), (103), as well as (0006) for the MoTe₂ nanoparticles. MoSe₂ presented the smallest size of the nanoparticles, followed by MoTe₂ and, lastly, by MoS₂. These results agreed with the results obtained using SEM analysis. For the optical properties of the nanoparticles, UV–Vis and PL were used. The shift of the peaks from the red shift (600 nm) to the blue shift (270–275 nm and 287–289 nm (UV–Vis)) confirmed that the nanoparticles were quantum-confined. The application of the MoX₂ NPs in QDSSCs was performed, with MoSe₂ presenting the greatest PCE of 7.86%, followed by MoTe₂ (6.93%) and, lastly, by MoS₂, with the PCE of 6.05%.