新型阴极材料Ba0.5Sr0.5Co0.8Fe0.2O3-σ制备与性能研究

Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-σ(BSCF), a new cathode material for solid oxide fuel cell (SOFC), was synthesized by polyacrylicacid (PAA) method. The lattice structures of samples calcined at different temperatures were characte-rized by XRD. Shrinkage, porosity and pore size of the porous BSCF as a function of sintering temperature were investigated. It was found that the cubic perovskite structure could be formed after calcination at 800 ℃ for 2 h, but not well crystallized as seen from some unknown phases, and the pure cubic perovskite structure was formed after calcination at 1 150 ℃ for 2 h. The particle size of BSCF was less than 1～2 μm. The shrinkage of the porous BSCF increased with sintering temperature, but the opposite was true for the porosity. After sintering at 1 100 ℃ for 4 h, the porous BSCF was still in an appropriate structure, with porosity of 29% and electrical conductivity above 400 S·cm^-1.     

Sr2CeO4蓝色荧光粉体材料的柠檬酸盐分解法合成与表征

Pure Sr₂CeO₄ nanosized phosphors has been successfully synthesized via a citrate decomposition method at a temperature as low as 900 ℃. The particle sizes were estimated to be 80～120 nm by X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The particle sizes were determined at the temperature of pre-decomposition, and would increase with the annealed temperature. Meanwhile, the photoluminescence properties of nano-Sr₂CeO₄ were investigated.     

Eu3+离子在Ca2PbO4一维结构基质中的发光研究

A Eu³⁺-doped Ca₂PbO₄ with one-dimensional structure was prepared with a solid-state reaction method and its characteristics were investigated. The XRD results show that the substitution of Ca²⁺ by Eu³⁺ has no influence on the structure of Ca₂PbO₄. Under the excitation of ultraviolet light， the Ca₂PbO₄:Eu³⁺ phosphor exhibits strong red emission at about 618 nm which is assigned to the ⁵D₀- ⁷F₂ electric-dipole transition. The compounds Sr₂CeO₄ and Ca₂SnO₄ have the same crystal symmetry as that of Ca₂PbO₄ and it is found that the emission intensity of Ca₂PbO₄∶Eu³⁺ is higher than that of Sr₂CeO₄∶Eu³⁺ and lower than that of Ca₂SnO₄∶Eu³⁺. The excitation spectrum of Ca₂PbO₄∶Eu³⁺ appears to be a broad band with two peaks at about 289 nm and 340 nm. The former peak is attributed to the Eu³⁺-O₂- charge transfer transition， while the latter one may be related to the absorption of Ca₂PbO₄ host or its crystal defects.     

电镀烧结法制备Ti/SnO2-Sb2O4电极的研究

The Ti/SnO₂-Sb₂O₄ electrode has been prepared by the electroplate-sinter method. The effect of SbCl₃ adding amount and sintering temperature on its electrode lifetime and oxygen evolution potential were investigated by means of EDX, SEM and XRD analysis. The results indicated that the electrode appeared the best performance when the SbCl₃ adding amounts was 0.2g and the sintering temperature was 550℃. In optimized conditions Ti substrate was entirely covered by SnO₂-Sb₂O₄ and the combinations among them were tight. Due to the use of electroplate method, the electrical conductivity, the oxygen evolution potential and the electrode lifetime were increased, so the elec-tro-catalytic activity and the electrochemical stability of the prepared electrode were found to be superior.     

阴极材料LaFe0.8-xCuxNi0.2O3的合成和烧结性能

LaFe_0.8-xCu_xNi_0.2O₃ (x=0.0~0.2) (LFCN), a new cathode material of solid oxide fuel cell (SOFC), was synthesized by Co-precipitation method using sodium bicarbonate. The lattice structures of samples with different x contents were characterized by XRD. Porosity and density of the porous LaFe_0.8-xCu_xNi_0.2O₃ (x=0.0~0.1) as a function of sintering temperature were investigated. It was found that the orthorhombic structure could be formed after calcination at 900 ℃ for 4 h. The particle size of LFCN was about 350 nm. The density of the porous LFCN increased with sintering temperature, but the opposite was true for the porosity. On the other hand, at the same sintering temperature, the porosity of LaFe_0.8-xCu_xNi_0.2O₃ (x=0.0~0.1) decreased with increasing x contents. It is indicated that the dopant of Cu on LaFe_0.8Ni_0.2O₃ can facilitate the sintering of the materials. After sintering at 1 100 ℃ for 4 h, the porous LaFe_0.7Cu_0.1Ni_0.2O₃ was still with appropriate structure, and its porosity was 29%.     

球形La2O3∶Eu纳米晶的制备及其发光特性

The spheric La₂O₃∶Eu nanocrystals were prepared using NH₃·H₂O-NH₄HCO₃ mixture as precipitant. The material was characterized by FTIR, XRD and TEM techniques. The luminescence properties of Eu³⁺ in spheric La₂O₃ were measured by three dimension spectra, emission and excitation spectra. The results indicate that the La₂O₃∶Eu nanocrystals are in hexagonal phase by annealing at 800 ℃, the crystal size is about 30 nm. The maximum emission and excitation wavelength were determined by three dimensional spectroscopy to be at 591 nm and 394 nm, respectively. In emission spectrum the band at 591 nm and 612 nm are corresponding to ⁵D₀-⁷F₁ and ⁵D₀-⁷F₂ transition of Eu³⁺ ions. With increasing in annealing temperature the differences of intensity of the two transitions are increased. This phenomenon shows that the luminescence intensity of La₂O₃∶Eu nanocrystals can be tuned by changing annealing temperature.     

固溶体结构对Ca2-xSrxZn4Ti15O36∶Pr3+发光性质的影响

Ca_2-xSr_xZn₄Ti₁₅O₃₆∶Pr red long decay phosphor was synthesized by high temperature solid state reaction. Photoluminescence property and crystalline and unit cell parameters of the orthorhombic were investigated by fluorescence spectrophotometer and by powder X-ray diffraction, respectively. The emission intensity at 618 nm changes sharply when the concentration of Sr²⁺ (x) is less than 0.1 and the emission intensity reaches the maximum when x is equal to 0.007. There is an obviously broad excitation band at 270 nm when x is equal to 0.003 and it disappears gradually when x is over 0.01. The unit cell a parameter of Ca_2-xSr_xZn₄Ti₁₅O₃₆∶Pr decreases while c parameter increases with the increases of the concentration of the doped Sr²⁺. When x is over 0.1 the value of the unit cell parameters a and c become stable. TL peaks of Ca₂Zn₄Ti₁₅O₃₆∶Pr, Ca_1.993Sr_0.007Zn₄Ti₁₅O₃₆∶0.002Pr³⁺, 0.002Na⁺, are located at 62 ℃, 88 ℃, respectively, which indicates that there are deeper traps in Ca_1.993Sr_0.007Zn₄Ti₁₅O₃₆∶0.002Pr³⁺, 0.002Na⁺.     

CexPr1-xO2-δ复合氧化物的XRD和Raman表征

A series of Ce_xPr_1-xO_2-δ mixed oxides were synthesized by sol-gel method and characterized by Raman and XRD techniques. When x value was changed from 1.0 to 0.5, only a cubic phase CeO₂ was observed. The samples were very well crystallized on decreasing x from 0.50 to 0.99. For Ce_xPr_1-xO_2-δ samples 465 cm^-1 and 1 150 cm^-1 Raman peaks are attributed to the Raman active F_2g mode of CeO₂. The broad peak at about 570 cm^-1 in the region of 0.3 ≤x≤ 0.99 can be linked to lattice defects resulting in oxygen vacancies. The new band at about 195 cm^-1 may be attributed to the asymmetric vibration caused by the formation of oxygen vacancies. Calcination temperatures had great effect on the peak intensity for CeO₂ but less effect on Ce_0.8Pr_0.2O_2-δ in Raman spectra. It might be due to the transformation of the colors for the mixed oxides, the insertion of Pr atom into the ceria lattice could enhance the sintering resistance and thermal stability of the mixed oxides.     

纳米晶SnO2粉体的合成

Crystalline tin oxide nanoparticles were synthesized by the direct precipitation from the starting material granulated tin. TG-DTA of the precursor showed a heavy weight loss at about 130℃ accompanied by an endothermic peak， two exothermic peaks above 200℃ accompanied by small weight loss indicated the decomposition and the oxidation of residual NO₃^- ion and PEG. XRD showed that obtained particles agreed well with the determination result of bulk SnO₂. The broadened XRD patterns became sharper as the calcining temperature turned to higher， it was indicated that the growth of the particle was exhibited. The surface area of the particles calcined at 300℃ was 161.1m²·g^-1 and declined as the calcining temperature turned to higher. TEM showed an heavier agglomeration at higher temperature.     

Cr/CeO2体系及其对乙烷脱氢反应催化性能的研究

The dehydrogenation reaction of ethane over Cr/CeO₂ catalysts in presence of CO₂ was studied with fixed-bed micro-reactor. The Cr/CeO₂ catalysts of different Cr loading have been synthesized using impregnation techniques. The Cr/CeO₂ system has already been found to be active and selective in the reaction at around 740 ℃. The function of carbon dioxide is to remove coke and hydrogen to accelerate dehydrogenation of ethane. The results of catalysts characterizations indicated that Cr³⁺ and Cr⁶⁺ occurred on the surface of the catalysts. The 1.2 mmol Cr/100m₂ CeO₂ catalyst sample with a monolayer dispersion of Cr on CeO₂ support showed a stronger surface acidity and a maximum yield of ethylene of about 35.5% at 36.6% conversion of ethane.     

Sol-gel synthesis of K3InF6 and structural characterization of K2InC10O10H6F9, K3InC12O14H4F18 and K3InC12O12F18

K₃InF₆ is synthesized by a sol-gel route starting from indium and potassium acetates dissolved in isopropanol in the stoichiometry 1:3, with trifluoroacetic acid as fluorinating agent. The crystal structures of the organic precursors were solved by X-ray diffraction methods on single crystals. Three organic compounds were isolated and identified: K₂InC₁₀O₁₀H₆F₉, K₃InC₁₂O₁₄H₄F₁₈ and K₃InC₁₂O₁₂F₁₈. The first one, deficient in potassium in comparison with the initial stoichiometry, is unstable. In its crystal structure, acetate as well as trifluoroacetate anions are coordinated to the indium atom. The two other precursors are obtained, respectively, by quick and slow evaporation of the solution. They correspond to the final organic compounds, which give K₃InF₆ by decomposition at high temperature. The crystal structure of K₃InC₁₂O₁₄H₄F₁₈ is characterized by complex anions [In(CF₃COO)₄(OH_x)₂]^(5−2x)− and isolated [CF₃COOH_2−x]^(x−1)− molecules with x=2 or 1, surrounded by K⁺ cations. The crystal structure of K₃InC₁₂O₁₂F₁₈ is only constituted by complex anions [In(CF₃COO)₆]³⁻ and K⁺ cations. For all these compounds, potassium cations ensure only the electroneutrality of the structure. IR spectra of K₂InC₁₀O₁₀H₆F₉ and K₃InC₁₂O₁₂F₁₈ were also performed at room temperature on pulverized crystals.     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

Non-centrosymmetric Ba3Ti3O6(BO3)2

The compound previously reported as Ba₂Ti₂B₂O₉ has been reformulated as Ba₃Ti₃B₂O₁₂, or Ba₃Ti₃O₆(BO₃)₂, a new barium titanium oxoborate. Small single crystals have been recovered from a melt with a composition of BaTiO₃:BaTiB₂O₆ (molar ratio) cooled between 1100°C and 850°C. The crystal structure has been determined by X-ray diffraction: hexagonal system, non-centrosymmetric space group, a=8.7377(11) Å, c=3.9147(8) Å, Z=1, wR(F²)=0.039 for 504 unique reflections. Ba₃Ti₃O₆(BO₃)₂ is isostructural with K₃Ta₃O₆(BO₃)₂. Preliminary measurements of nonlinear optical properties on microcrystalline samples show that the second harmonic generation efficiency of Ba₃Ti₃O₆(BO₃)₂ is equal to 95% of that of LiNbO₃.     

Ion-beam irradiation of lanthanum compounds in the systems La2O3-Al2O3 and La2O3-TiO2

Thin crystals of La₂O₃, LaAlO₃, La_2/3TiO₃, La₂TiO₅, and La₂Ti₂O₇ have been irradiated in situ using 1 MeV Kr²⁺ ions at the Intermediate Voltage Electron Microscope-Tandem User Facility (IVEM-Tandem), Argonne National Laboratory (ANL). We observed that La₂O₃ remained crystalline to a fluence greater than 3.1×10¹⁶ ions cm⁻² at a temperature of 50 K. The four binary oxide compounds in the two systems were observed through the crystalline-amorphous transition as a function of ion fluence and temperature. Results from the ion irradiations give critical temperatures for amorphisation (T_c) of 647 K for LaAlO₃, 840 K for La₂Ti₂O₇, 865 K for La_2/3TiO₃, and 1027 K for La₂TiO₅. The T_c values observed in this study, together with previous data for Al₂O₃ and TiO₂, are discussed with reference to the melting points for the La₂O₃-Al₂O₃ and La₂O₃-TiO₂ systems and the different local environments within the four crystal structures. Results suggest that there is an observable inverse correlation between T_c and melting temperature (T_m) in the two systems. More complex relationships exist between T_c and crystal structure, with the stoichiometric perovskite LaAlO₃ being the most resistant to amorphisation.     

Synthesis, crystal structure, infrared and Raman spectra of Sr4Cu3(AsO4)2(AsO3OH)4·3H2O and Ba2Cu4(AsO4)2(AsO3OH)3

The two new compounds, Sr₄Cu₃(AsO₄)₂(AsO₃OH)₄·3H₂O (1) and Ba₂Cu₄(AsO₄)₂(AsO₃OH)₃(2), were synthesized under hydrothermal conditions. They represent previously unknown structure types and are the first compounds synthesized in the systems SrO/BaO-CuO-As₂O₅-H₂O. Their crystal structures were determined by single-crystal X-ray diffraction [space group C2/c, a=18.536(4) Å, b=5.179(1) Å, c=24.898(5) Å, β=93.67(3)°, V=2344.0(8) Å³, Z=4 for 1; space group P4₂/n, a=7.775(1) Å, c=13.698(3) Å, V=828.1(2) Å³, Z=2 for 2]. The crystal structure of 1 is related to a group of compounds formed by Cu²⁺-(XO₄)³⁻ layers (X=P⁵⁺, As⁵⁺) linked by M cations (M=alkali, alkaline earth, Pb²⁺, or Ag⁺) and partly by hydrogen bonds. In 1, worth mentioning is the very short hydrogen bond length, D···A=2.477(3) Å. It is one of the examples of extremely short hydrogen bonds, where the donor and acceptor are crystallographically different. Compound 2 represents a layered structure consisting of Cu₂O₈ centrosymmetric dimers crosslinked by As1φ₄ tetrahedra, where φ is O or OH, which are interconnected by Ba, As2 and hydrogen bonds to form a three-dimensional network. The layers are formed by Cu₂O₈ centrosymmetric dimers of CuO₅ edge-sharing polyhedra, crosslinked by As1O₄ tetrahedra. Vibrational spectra (FTIR and Raman) of both compounds are described. The spectroscopic manifestation of the very short hydrogen bond in 1, and ABC-like spectra in 2 were discussed.     

A new 2212-type stair like structure: Bi14Sr21Fe12O61, m=5 member of the generic [Bi2Sr3Fe2O9]m[Bi4Sr6Fe2O16] family

A new oxide, Bi₁₄Sr₂₁Fe₁₂O_61, with a layered structure derived from the 2212 modulated type structure Bi₂Sr₃Fe₂O₉, was isolated. It crystallizes in the I2 space group, with the following parameters: a=16.58(3) Å, b=5.496(1) Å, c=35.27(2) Å and β=90.62°. The single crystal X-ray structure determination, coupled with electron microscopy, shows that this ferrite is the m=5 member of the [Bi₂Sr₃Fe₂O₉]_m[Bi₄Sr₆Fe₂O₁₆] collapsed family. This new collapsed structure can be described as slices of 2212 structure of five bismuth polyhedra thick along , shifted with respect to each other and interconnected by means of [Bi₄Sr₆Fe₂O₁₆] slices. The latter are the place of numerous defects like iron or strontium for bismuth substitution; they can be correlated to intergrowth defects with other members of the family.     

Raman scattering investigations on lanthanum-doped Bi4Ti3O12-SrBi4Ti4O15 intergrowth ferroelectrics

The ferroelectric ceramics of Bi₄Ti₃O₁₂, SrBi₄Ti₄O₁₅, and lanthanum-doped Bi₄Ti₃O₁₂-SrBi₄Ti₄O₁₅ were synthesized, and their Raman spectra were investigated. La-doping resulted in the enlargement of remnant polarization of Bi₄Ti₃O₁₂-SrBi₄Ti₄O₁₅. The structure of the Bi₂O₂ layers and TiO₆ octahedra of the intergrowth was found to be different from those of Bi₄Ti₃O₁₂ and SrBi₄Ti₄O₁₅. La³⁺ ions exhibit pronounced selectivity for the occupation of A site as La content is lower than 0.50, and tend to be incorporated into Bi₂O₂ layers when the La content is higher than 0.50. Lanthanum substitution brings about the structural phase transition in Bi₄Ti₃O₁₂-SrBi₄Ti₄O₁₅. The variation of ferroelectric property may be attributed to combined contribution from the decreasing of the oxygen vacancies, the relaxation of the lattice distortion, the destroying of the insulation and the space charge compensation effects of the Bi₂O₂ slabs.     

g-C_3N_4/CaTi_2O_5复合材料制备及其光催化性能

利用类石墨氮化碳(g-C_3N_4)和亚稳相钙钛氧化物(CaTi_2O_5)固相法制备C_3N_4/CaTi_2O_5复合材料。利用X射线衍射(XRD)、金相显微镜、扫描电子显微镜(SEM)及附带能谱分析仪(EDS)和N2吸附-脱附对样品的显微结构和比表面积进行检测分析,并用紫外-可见吸收光度计(UV-Vis)测试了样品的光吸收性能,研究C_3N_4与CaTi_2O_5物质的量之比(nC_3N_4/nCaTi_2O_5)对C_3N_4/CaTi_2O_5复合样品的物相结构和微观形貌的影响,同时考察C_3N_4/CaTi_2O_5复合样品在可见光照射下光催化降解罗丹明染料效果。实验结果表明:相比纯C_3N_4和CaTi_2O_5样品,C_3N_4/CaTi_2O_5复合样品在可见光下具有较高的光催化性能,随着nC_3N_4/nCaTi_2O_5增加,样品的光催化降解率随之增加而后降低,当nC_3N_4/nCaTi_2O_5=1∶1时,样品的光催化降解率达到最大值99.5%,并且循环重复利用5次后,样品的光催化剂降解率仍几乎保持不变。复合样品光催化性能提高主要归因于复合能级结构有效地抑制了电子和空穴复合所致。     

Crystal growth, structural characterization and magnetic properties of Ca3CuRhO6, Ca3Co1.34Rh0.66O6 and Ca3FeRhO6

Single crystals of Ca₃CuRhO₆, Ca₃Co_1.34Rh_0.66O₆ and Ca₃FeRhO₆ were synthesized by high temperature flux growth in molten K₂CO₃ and structurally characterized by single crystal X-ray diffraction. While Ca₃Co_1.34Rh_0.66O₆ and Ca₃FeRhO₆ crystallize with trigonal (rhombohedral) symmetry in the space group , Z=6: Ca₃Co_1.34Rh_0.66O₆a=9.161(1) Å, c=10.601(2) Å; Ca₃FeRhO₆a=9.1884(3) Å, c=10.7750(4) Å; Ca₃CuRhO₆ adopts a monoclinic distortion of the K₄CdCl₆ structure in the space group C2/c, Z=4: a=9.004(2) Å, b=9.218(2) Å, c=6.453(1) Å, β=91.672(5). All crystals of Ca₃CuRhO₆ examined were twinned by pseudo-merohedry. Ca₃CuRhO₆, Ca₃Co_1.34Rh_0.66O₆, and Ca₃FeRhO₆ are structurally related and contain infinite one-dimensional chains of alternating face-sharing RhO₆ octahedra and MO₆ trigonal prisms. In the monoclinic modification, the copper atoms are displaced from the center of the trigonal prism toward one of the rectangular faces adopting a pseudo-square planar configuration. The magnetic properties of Ca₃CuRhO₆, Ca₃Co_1.34Rh_0.66O₆, and Ca₃FeRhO₆ are discussed.     

Magnetic diphase nanostructure of ZnFe2O4/γ-Fe2O3

Magnetic diphase nanostructures of ZnFe₂O₄/γ-Fe₂O₃ were synthesized by a solvothermal method. The formation reactions were optimized by tuning the initial molar ratios of Fe/Zn. All samples were characterized by X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, and Raman spectra. It is found that when the initial molar ratio of Fe/Zn is larger than 2, a diphase magnetic nanostructure of ZnFe₂O₄/γ-Fe₂O₃ was formed, in which the presence of ZnFe₂O₄ enhanced the thermal stability of γ-Fe₂O₃. Further increasing the initial molar ratio of Fe/Zn larger than 6 destabilized the diphase nanostructure and yielded traces of secondary phase α-Fe₂O₃. The grain surfaces of diphase nanostructure exhibited a spin-glass-like structure. At room temperature, all diphase nanostructures are superparamagnetic with saturation magnetization being increased with γ-Fe₂O₃ content.