Infrared and Structural Properties of Y1?xNdxBa2Cu3O7?δ (0 ≤ x ≤ 1)

Infrared and structural properties of Y_1–x Nd _x Ba₂Cu₃O_7– (0 x 1) were investigated using infrared absorption spectroscopy and X-ray powder diffraction. The unit cell parameters of the samples were defined using X-ray diffraction data. The resistance measurements showed that the samples revealed superconductivity in the temperature range of 80–100 K. It was observed that by the substitution of Nd to Y in YBa₂Cu₃O_{7 –} IR band at 573 cm^–1 that is assigned as Cu–O axial antisymmetric stretching mode shifts to 533 cm^–1 while the band at 620 cm^–1 that is due to Cu–O symmetric stretching mode in YBa₂Cu₃O_7– shifts to 588 cm^–1.     

Specific Heat of LaMnO3 + δ at 50 K ≤ T ≤ 160 K

We have developed a shell model, which includes the long-range coulomb, van der Waals interaction, and the short-range Hafemeister–Flygare repulsive interaction operative up to second neighbor atom to study the cohesive and thermal properties of LaMnO_{3 +} . The results on cohesive energy obtained by us are in good agreement with that of calculated value by DeSouza et. al. (R. A. DeSouza, M. S. Islam, and E. I. Tiffee, J. Mater. Chem. 9, 1621 (1999)). In addition, we have also calculated molecular force constant (f), compressibility (), restrahlen frequency (_o), Debye temperature (_D), and the low temperature specific heat at 50 K T 160 K. Our results on Debye temperature and specific heat for the temperature range 50 K T 160 K are closer to the recently measured data with an automated quasi-adiabatic pulse technique.     

Phase composition and structure of La1 ? x Ca x MnO3 + δ (0 ≤ x ≤ 0.2) solid solutions

A structural phase diagram of La_{1 − x} Ca _x MnO_{3 + δ} (0 ≤ x ≤ 0.2) solid solution in air has been constructed for the first time, and the equilibrium T-x fields of the monoclinic, orthorhombic, and rhombohedral phases in this system have been outlined. The transitions between these phases are accompanied by sharp changes in lattice parameters, suggesting that they are first-order. Original Russian Text ? S.Kh. Estemirova, A.M. Yankin, S.G. Titova, V.F. Balakirev, Yu.E. Turkhan, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 11, pp. 1387–1392.     

Emissivity and Optical Properties of Thermochromic Material La0.7Ca0.3?xSrxMnO3?(0 ≤ x ≤ 0.3)

La_0.7Ca_0.3−x Sr _x MnO₃ (0 ≤ x ≤ 0.3) (LCSMO) is a thermochromic material. The material can show a phase transition from ferromagnetic-metal to paramagnetic-insulator under the appropriate doping level (x). In this paper, LCSMO compounds were synthesized by a conventional solid-state reaction method. The normal emissivity and the spectral reflectance of LCSMO with different doping levels (x) are experimentally investigated. Based on the spectral reflectance data, the optical constants (refractive index n and extinction coefficient k) are calculated by using Kramers–Kronig (K–K) relations. Then, the emissivity changing mechanism is discussed. The experimental results show that the emissivity of LCSMO increases with increasing temperature. For the samples with x = 0.1 and 0.15, their emissivity has a sudden change in the vicinity of the phase transition temperature T _p.     

钙钛矿型Gd1-xDyxMnO3（0≤x≤1）的水热合成及磁性表征

通过环境友好的水热法制备了钙钛矿型稀土锰酸盐Gd1-xDyxMnO3(0≤x≤1),该系列化合物具有正交结构(属于pbnm空间群)。在合成反应中,Mn(OH)2在强碱体系下被空气中O2氧化生成包含Mn3+的反应前驱物;锰酸盐的晶体生长、反应温度和碱度对其有明显的影响。磁性表征结果显示Dy3+对Gd3+的取代引起了化合物低温磁有序的竞争。     

Chemically inducing room temperature spin-crossover in double layered magnetic refrigerants Pr1.4+xSr1.6-xMn2O7 (0.0 ≤ x ≤ 0.5)

The height of total entropy (S_T) for a magnetic refrigerant material is essentially concerned with the magnetic and structural transitions.However,the participation of such transitions in layered materials is not well understood.Therefore,the purpose of this work is to investigate the interplay between double layer lattice with their single perovskite counterpart,to achieve optimal magnetocaloric performance.A series of self-doped Pr_1.4+xSr_1.6-xMn₂O     

LiMn2-2xLixNixO4(0≤X≤0.1)阴极材料的结构和电化学性能

采用高温固相法，合成了LiMn2-2xLixNixO4（x=0．03、0．05、0．075、0．100）试样，用X射线衍射（XRD）和场发射扫描电镜（FESEM）对试样的晶体结构和形貌进行了表征，从试样的充放电性能，室温和高温下（55℃）循环性能等方面，并结合X射线吸收精细结构（X-ray absorption fine structure，XAFS）所得到的试样中MnO6八面体中键长的变化分析了锂镍协同掺杂对尖晶石结构的稳定作用。实验表明：与尖晶石LiMn2O4相比，LiMn2-2xLixNixO4试样在室温和55℃时具有良好的容量保持能力，是由于Li，Ni协同掺杂对试样的结构起了稳定作用。     

Synthesis and magnetic properties of nanocrystalline Y1 ? xCdxFeO3 ? δ (0 ≤ x ≤ 0.2)

We report the synthesis of Y_{1 − x} Cd _x FeO_{3 − δ} nanocrystals in the range x = 0–0.2. The Y_{1 − x} Cd _x FeO_{3 − δ} materials were shown to be single-phase by X-ray diffraction, with an average crystallite size from 23 to 34 nm, depending on composition. With increasing cadmium oxide content, the size of the Y_{1 − x} Cd _x FeO_{3 − δ} nanocrystals decreases and their magnetization rises.     

Electrical conductivity of LaCoxFe1 ? xO3 ? δ and LaLi0.1CoxFe0.9 ? xO3 ? δ (0 ≤ x ≤ 0.4) oxides

We have studied the effect of Co and Li concentrations on the phase composition and electrical conductivity of LaCo _x Fe_{1 − x} O_{3 − δ} and LaLi_0.1Co _x Fe_{0.9 − x} O_{3 − δ} perovskite-like oxides synthesized in air at 1470 K. Single-phase materials with an orthorhombic crystal structure were obtained in the range 0 ≤ x ≤ 0.3. The composition dependences of conductivity have a minimum at x _c = 0.1 and 0.2, respectively. In the range x > 0.1, the conductivity of LaCo _x Fe_{1 − x} O_{3 − δ} increases with increasing Co concentration for T > 700 K and decreases for T < 600 K. The conductivity of La(Li_0.1Co _x Fe_{0.9 − x} )O_{3 − δ} in the range 0 ≤ x ≤ 0.1 and for x ≥ 0.2 increases with Co concentration throughout the temperature range studied.     

Self-propagating combustion synthesis of Pb1?xSrxZrO3 (0 ≤ x ≤ 0·20) ceramics and their dielectric properties

Lead strontium zirconate, Pb_1−x Sr _x ZrO₃ (0 ≤ x ≤ 0·20) ceramics, were prepared by novel glycinenitrate self-propagating combustion technique. The crystal structure of the ceramics was investigated as a function of composition via X-ray diffraction (XRD). The XRD patterns obtained on these powders showed the formation of pure orthorhombic phase of lead strontium zirconate without impurities and all the compounds retained the orthorhombic structure. The samples were sintered at 900–1100°C for 2 h. It has been observed that the dielectric constant decreases with increase in strontium content (100 kHz). In all compositions, dielectric constant showed a peak at transition temperature and the magnitude of the peak was found to decrease with strontium doping level.     

Spin Gap Effects on Bulk R1+xba2?x Cu3O7?δ (R=Eu or Nd and 0≤x≤0.4)

Spin gap effects on the underdoping states of the bulk system of R_1+x Ba_2–x Cu₃O_7– (R = Eu or Nd and 0 x 0.4) were investigated through transport property measurements. The underdoping states were achieved by, alternatively substituting R³⁺ for Ba²⁺ ions in the system rather than adjusting the oxygen deficiency. The excess R³⁺ ions were to occupy the Ba sites of the crystalline lattice as revealed from Rietveld analysis for powder X-ray diffraction. The underdoped materials were observed to first undergo spin pairing transition in the temperature range well above T _c, and come across with superconducting transition at T _c. The increasing feature observed for spin gap temperature and the decreasing one for T _c, as the concentration of holes decreases, are in qualitatively good agreement with theoretical predictions from the mean-field RVB model.     

La3+ effect on dipole ordering in Pb1 ? xLax[Zr0.7Sn0.2Ti0.1][1 ? x/4]O3(0 < x ≤ 0.03) solid solutions

We have studied temperature- and electric-field-induced phase transitions in ceramic samples of Pb_{1 − x} La _x [Zr_0.7Sn_0.2Ti_0.1]_{1 − x /4}O₃ (0 < x ≤ 0.03) solid solutions. The results indicate that La³⁺ doping to x > 0.005 impedes long-range dipole-dipole interactions and stabilizes nonpolar phases below the Curie temperature. At a constant La³⁺ concentration, lowering the temperature facilitates a field-induced transition to a ferroelectric state. In thermally depoled samples, the first antiferroelectric → ferroelectric switching usually requires a higher bias voltage than do subsequent switchings. Original Russian Text ? E.A. Bikyashev, E.A. Reshetnikova, M.I. Tostunov, 2009, published in Neorganicheskie Materialy, 2009, Vol. 45, No. 8, pp. 990–995.     

Synthesis, structural and ferromagnetic properties of La1?xKxMnO3 (0·0 ≤ x ≤ 0·25) phases by solution combustion method

We describe the solution combustion synthesis and characterization of La_1–x K _x MnO₃ (0·0 ≤ x ≤ 0·25) perovskite phases, which is a low temperature initiated, rapid route to prepare metal oxides. As-synthesized compounds are amorphous in nature; crystallinity was observed on heating at 800°C for 5 min. Structural parameters were determined by the Rietveld refinement method using powder XRD data. Parent LaMnO₃ compound crystallizes in the orthorhombic structure (space group Pbnm, No. 62). Potassium substituted compounds were crystallized with rhombohedral symmetry (space group R-3c, No. 167). The ratio of the Mn³⁺/Mn⁴⁺ was determined by the iodometric titration. The Fourier transform infrared spectrum (FT-IR) shows two absorption bands for Mn-O stretching vibration (ν _s mode), Mn-O-Mn deformation vibration (ν _b mode) around 600 cm⁻¹ and 400 cm⁻¹ for the compositions, x = 0·0, 0·05 and 0·10. Four-probe electrical resistivity measurements reveal a composition controlled metal to insulator transition (T _M–I), the maximum T _M–I was observed for the composition La_0·85K_0·15MnO₃ at 287 K. Room temperature vibrating sample magnetometer data indicate that for the composition up to x = 0·10, the compounds are paramagnetic whereas composition with x = 0·15, 0·20 and 0·25 show magnetic moments of 27, 29 and 30 emu/g, respectively.     

Sr1-xBixFeO3-δ(x≤0.50)的柠檬酸盐法制备和导电性

采用柠檬酸法制备了Ｓｒ１－ｘＢｉｘＦｅＯ３－δ（ｘ≤０．５０）系列氧离子－电子混合导体,并采用ＸＲＤ,ＩＲ,ＴＧ,ＤＴＡ和交流复阻抗技术对产物进行了表征。初始凝胶经自燃和８００℃下预烧,可得纯相钙钛矿产物粉体,其结构与ＳｒＦｅＯ３相似,为正交对称性。     

Li0.5La0.5TiO3包覆LiNil/3Co1/3Mnl/3O2材料的研究

以Li0.5La0.5TiO3为包覆物,制备了固体电解质包覆的LiNil/3Co1/3Mnl/3O2正极材料。采用XRD、SEM对材料进行了表征:XRD显示未包覆的材料具有α-NaFeO2层状结构,粒径在200～300nm之间,包覆后材料粒径略有增大,包覆层具有ABO3型固体电解质结构。包覆层的致密程度及材料的循环稳定性与热处理温度有关。包覆后400℃热处理得到的材料首次放电比容量为185mAh/g,较未包覆材料容量有所提高,50次循环后其容量仍能达到156.5mAh/g,表明包覆物Li0.5La0.5TiO3对LiNil/3Co1/3Mnl/3O2具有保护作用。     

MgO-Al2O3-SiO2-TiO2-Y2O3玻璃的弹性模量

根据硬盘基板用材料的要求，制备了MgO-Al2O3-SiO2-TiO2-Y2O3高弹性模量玻璃（120GPa)，玻璃的弹性模量随组成的变化服从Makishima-Mackenzie理论，MgO,Al2O3,TiO2,Y2O3等具有较高单位体积离解能的氧化物有利于提高玻璃的弹性模量，但玻璃弹性模量的理论计算值低于测试值，这是因为Makishima-Mackenzie理论没有考虑玻璃内阳离子的具体配位，对MgO,Y2O3堆积密度因子的堆导存在误差，因此利用Makishima-Mackenzie理论发展高弹性模量玻璃时应对MgO,Y2O3等氧化物的计算进行修正。     

Na0.5Bi2.5Nb2O9-Na0.5Bi4.5Ti4O15材料的微观结构及电性能

采用固相烧结法制备了铋层结构铁电材料(1-x)Na0.5Bi2.5Nb₂O₉-xNa0.5Bi4.5Ti₄O₁₅(NBNO-NBT-x)。结合XRD、SEM以及电子能谱分析推测NBNO-NBT-0.5陶瓷主要为2-4层的共生结构NaBi₇Ti₄Nb₂O₂₄,由Na0.5Bi2.5Nb₂O₉和Na0.5Bi4.5-Ti₄O₁₅沿c轴交替排列。晶格结构的不对称性增加导致晶格应力增大,而NBNO和NBT两种单体系的复合将进一步加大离子无序和结构无序,从而使该组成的陶瓷表现出不同于两种单体系的微观结构和电性能。NBNO-NBT-0.5陶瓷的晶粒长度大于20 μm,厚度小于2 μm,晶粒长径比明显高于NBNO和NBT;而相比于两种单体其居里温度TC降低,居里峰宽化,高温介电损耗增大,电导激活能减小,铁电、压电性能降低。     

La0.5Y0.5Ni4.8Mn0.1Al0.1和La0.5Y0.5Ni4.8Al0.2合金的储氢性能研究

针对两种新型稀土型储氢合金La0.5Y0.5Ni4.8Mn0.1Al0.1和La0.5Y0.5Ni4.8Al0.2的储氢特性进行研究分析。实验表明,相同温度下,La0.5Y0.5Ni4.8Mn0.1Al0.1和La0.5Y0.5Ni4.8Al0.2合金的PCT曲线基本重合,且都具有优良的吸氢动力学性能;相比之下,后者的滞后系数要小于前者,吸氢量较大,吸氢速率也较快,故其储氢性能较优。300次吸放氢循环实验结果表明,La0.5Y0.5Ni4.8Al0.2合金的吸氢动力学性能虽然略有下降,但抗粉化性能较好。     

La0.85Sr0.15Cr0.9Ni0.1O3-δCe0.8Sm0.2O1.9作为SOFC阳极材料的研究

较低的催化活性大大地限制了La0．85Sr0．15Cr0．9Ni0．1O3-δ-（LSCN）作为直接碳氢化合物燃料SOFC阳极材料的应用．本文尝试用Pechini法合成LSCN，并按重量比1：1向其中加入纳米Ce0.8Sm0.2O1.9（SDC）作为阳极材料．经1500℃高温烧结12h后，LSCN与SDC以及电解质YSZ仍可以保持各自独立的相结构．加入SDC没能提高阳极的电导率，但由于改善了阳极电解质界面的结合状况，扩展了电极反应的活性区域，使阳极材料的极化性能有了提高．显微结构观察品示．LSCN-SDC阳极存甲烷与氧中使用时没有碳沉积现象．     

Sc2O3-Y2O3-ZrO2陶瓷材料热物理性能

采用固相合成法制备了6.3%Sc_2O_3-1.3%Y2O3-92.4%ZrO_2(摩尔分数)陶瓷材料。分别利用X射线衍射、示差扫描量热法、高温热膨胀仪和激光导热法对陶瓷材料的物相组成、高温相稳定性、热膨胀系数和热扩散等性能进行了表征。结果表明,经1600℃烧结6h,该陶瓷材料由单一的立方相结构组成,具有良好的高温相稳定性,热导率低于传统的6~8YSZ,是一种良好的热障涂层候选材料。