Investigation on the low-frequency mechanical properties of La0.6Sr0.4Co1−xFexO3−δ materials

The low-frequency mechanical properties of La_0.6Sr_0.4Co_1−xFe_xO_3−δ (0 ≤ x ≤ 0.8) materials have been measured using a computer-controlled pendulum. For undoped sample, five internal friction peaks (P0, P1, P2, P3 and P4) were observed. However, with the Fe doping, only two peaks (P3 and P4) were found at high temperature. The peaks of P0 and P1 have the feature of phase transition-induced internal friction, while the peaks of P2, P3 and P4 are the relaxation-type. From the analysis, it is suggested that the peak of P0 is due to the phase separation and the peak of P1 is related to the ferromagnetic (FM)-paramagnetic (PM) phase transition. For the peaks of P2, P3 and P4, they were associated with the motion of domain walls. The formation of this kind of domain structure is a consequence of a transformation from the paraelastic cubic phase to ferroelastic rhombohedral phase.     

Role of BaO/SrO layers in deciding the electronic structure of Cu0.3Co0.7Ba2−xSrxYCu2O7+δ (CoCu-1212) x = 0, 1 and 2

In this paper we report the change in electronic structure of Cu_0.3Co_0.7Ba_2−xSr_xYCu₂O_7+δ with change in structural pressure. Rietveld refined X-ray diffraction (XRD) pattern shows that the samples are phase pure. Decrease in lattice parameters with increasing x, confirms replacement by Sr ion at Ba ion site. The calculated tolerance factor of the systems is in accord with lattice parameter changes. The X-ray photoelectron spectroscopy (XPS) is made to find out the variation in ionic state of Co and Cu with ionic size variation in BaO/SrO layers. Effect of the same on the electronic structure and transport properties is explored. The XPS measurement reveals that Cu is in mixed 1+/2+ state and variation in valence state is non-monotonous with increasing x. Whereas Co is in mixed 3+/4+ state and with increasing x its valence state is increasing. The observed changes in electronic structure are subject of structural changes. The resistivity measurement shows that normal state conductivity decreases with increasing x. Resistivity behaviour indicates about holes in Cu/CoO_x planes taking part in charge transport. The magnetic measurement (M-T and M-H) shows that paramagnetic nature for all the compositions. The presence of Cu ions in Cu/CoO_x chains/planes results in paramagnetic behaviour.     

Enhanced cycling stability of Mg–F co-modified LiNi0.6Co0.2Mn0.2–yMgyO2–zFz for lithium-ion batteries

The layered LiNi_0.6Co_0.2Mn_0.2–yMg_yO_2–zF_z (0≤y≤0.12, 0≤z≤0.08) cathode materials were synthesized by combining co-precipitation method and high temperature solid-state reaction, with the help of the ball milling, to investigate the effects of F–Mg doping on LiNi_0.6Co_0.2Mn_0.2O₂. Compared with previous studies, this doping treatment provides substantially improved electrochemical performance in terms of initial coulombic efficiency and cycle performance. The LiNi_0.6Co_0.2Mn_0.11Mg_0.09O_1.96F_0.04 electrode delivers an high capacity retention of 98.6% during the first cycle and a discharge capacity of 189.7 mA·h/g (2.8–4.4 V at 0.2C), with the capacity retention of 96.3% after 100 cycles. And electrochemical impedance spectroscopy(EIS) results show that Mg–F co-doping decreases the charge-transfer resistance and enhances the reaction kinetics, which is considered to be the major factor for higher rate performance. It is demonstrated that LiNi_0.6Co_0.2Mn_0.11Mg_0.09O_1.96F_0.04 is a promising cathode material for lithium-ion batteries for excellent electrochemical properties.     

Thermoelectric properties of n-type Ca1−xDyxMn1−yNbyO3−δ compounds (x = 0, 0.02, 0.1 and y = 0, 0.02) prepared by spray-drying method

We report the high temperature thermoelectric properties of Ca_1−xDy_xMn_1−yNb_yO_3−δ (x = 0, 0.02, 0.1 and y = 0, 0.02) synthesized by spray-drying method. A maximum power factor (PF) value of 2.65 μW K⁻² cm⁻¹ is obtained at 1100 K for CaMn_0.98Nb_0.02O_3−δ. This represents an improvement of about 75% with respect to undoped CaMnO_3−δ sample at the same temperature. We also provide a complete structural characterization of the samples.     

Phase composition and magnetic properties of phases in Sm2(Fe1 ? x ? yMnxSiy)17 alloys (with 0 ≤ x ≤ 0.1 and 0 ≤ y ≤ 0.3)

The phase composition of the Sm₂(Fe_{1 − x − y} Mn _x Si _y )₁₇ alloys (0 ≤ x ≤ 0.1 and 0 ≤ y ≤ 0.3) annealed at 1273 K has been studied. The simultaneous alloying of the alloys with manganese and silicon has been found to change their phase composition. At T < 1473 K, the Th₂Zn₁₇-type structure of the Sm₂(Fe,Mn,Si)₁₇ compound transforms into the Th₂Ni₁₇-type structure, which exists only in the presence of all these four elements. At x ≥ 0.05 and y = 0.2, the Sm(Fe,Mn,Si)₁₂ and SmMn₂Si₂ compounds are formed, and the Mn and Si concentrations in Sm₂(Fe,Mn,Si)₁₇ decrease. As a result, we failed to realize the Sm₂(Fe,Mn,Si)₁₇ compound with the uniaxial magnetic anisotropy in these alloys. Manganese additions slightly decrease the Curie temperature T _C of the Sm₂(Fe_{1 − x} Mn _x )₁₇ compound. The additional alloying with silicon is accompanied by an increase in the Curie temperature of the Sm₂(Fe,Mn,Si)₁₇ compound; however, the T _C magnitude was found to be lower than that for manganese-free compounds with the same silicon concentration. Manganese additions also decrease the Curie temperature of the Sm(Fe,Mn,Si)₁₂ phase. The substitution of manganese for iron in the Sm₂Fe₁₇ compound substantially decreases the magnetization; additional alloying with silicon further decreases the magnetization, although the decrease is less abrupt.     

CSTR系统制备高性能Ni0.6Co0.2Mn0.2(OH)2及电化学性能研究

采用共沉淀法在CSTR(连续搅拌反应器系统)工艺体系中批量合成出镍钴锰三元氢氧化物前驱体Ni0.6Co0.2Mn0.2(OH)2 (622),掺入适量的Li2CO3高温焙烧后得到锂离子二次电池正极材料Li[Ni0.6Co0.2Mn0.2]O2。使用扫描电子显微镜(SEM)观察样品形貌,X射线衍射仪(XRD)及透射电子显微镜(TEM)分析合成样品的具体结构,充放电循环测试系统测试其电化学性能。SEM测试表明产物为二次粒子团聚而成类球形颗粒;XRD及TEM结果表明合成的样品具有典型的层状α-NaFeO2结构。在电压范围为2.8 V-4.3 V,0.2 C倍率条件下,首次充放电容量分别为206 mAh g-1 和176 mAh g-1,100次循环后容量保持率达到85%。     

Penetration of high-frequency electromagnetic field through bulk samples of La1? x Sr x MnO3 (0.33 ≤ x ≤ 0.60) manganites

Penetration of radio-frequency electromagnetic field through bulk samples of La_1−x Sr _x MnO₃ (0.33 ≤ x ≤ 0.60) manganites has been studied in the frequency range from 20 kHz to 30 MHz at temperatures from 300 to 400 K, which includes the temperature of the magnetic phase transition of some investigated compositions. It has been shown that, in spite of the differences in the static properties, the dynamic properties of the investigated compositions of these manganites are similar; the differences are mainly pronounced at frequencies higher than 1 MHz. In the ferromagnetic range, significant changes in the transmission coefficient have been observed for all compositions upon magnetization. The magnitudes of the initial dynamic magnetic permeability have been estimated. The changes in the transmission coefficient in the ferromagnetic region are mainly caused by changes in the dynamic magnetic permeability rather than by magnetoresistance. It is shown that in the paramagnetic temperature range the magnitude of the dynamic reversible permeability exceeds unity for all compositions, which supports the assumption on the retention of local magnetic ordering. Original Russian Text ? A.P. Nosov, A.B. Rinkevich, V.G. Vasil’ev, E.V. Vladimirova, 2008, published in Fizika Metallov i Metallovedenie, 2008, Vol. 106, No. 1, pp. 36–44.     

The maximum solubility of Y in α-Mg and composition ranges of Mg24Y5 − x and Mg2Y1 − x intermetallic phases in Mg-Y binary system

The solid solubility of Y in the α-Mg matrix and composition homogeneity ranges of Mg₂₄Y_5 − x and Mg₂Y_1 − x phases in the Mg-Y binary system are important parameters to understand solid-solution- and aging-strengthening effects of Mg-Y-based alloys. However, they are different among the various assessed Mg-Y phase diagrams which are based on limited experimental data, especially at temperatures below ∼850 K. Our experimental results by using both diffusion couple technique and alloy method are in good agreement each other, but much different from the presently accepted Mg-Y phase diagram. The results show that the maximum solubility of Y in the α-Mg matrix is 4.7 at.% Y, much larger than the current phase diagram. The determined composition homogeneity ranges of Mg₂₄Y_5 − x and Mg₂Y_1 − x phases are much wider than the present ones and shift remarkably to the Mg-rich corner of Mg-Y phase diagram.     

The effects of temperature and composition on the thermal conductivities of [(ZrO2)1−x(CeO2)x]0.92(Y2O3)0.08 (0 ? x ? 1) solid solutions

The thermal conductivities of [(ZrO₂)_1−x(CeO₂)_x]_0.92(Y₂O₃)_0.08 (0 ? x ? 1) solid solutions are studied in this paper. The incorporation of ZrO₂ and CeO₂ in the solid solution decreases the thermal conductivity compared with their end members (YSZ and YDC). The thermal conductivities of the solid solutions show clearly different temperature dependences in the ZrO₂-rich (0 ? x ? 0.5) region and in the CeO₂-rich region (0.5 ? x ? 1). The composition and the temperature dependence of the thermal conductivities are discussed based on established phonon scattering theories. We have concluded that the composition dependence of the thermal conductivity of this system is mainly controlled by the mass difference between Zr⁴⁺ and Ce⁴⁺, while the thermal conductivity-temperature relationship is dominated by the randomness of the defect distribution.     

CuO掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3无铅压电陶瓷的研究

用传统固相反应法在不同温度下烧结制备了不同含量CuO掺杂的0.45(Ba0.7Ca0.3)TiO3-0.55Ba(Zr0.2Ti0.8)O3(BCZT45)无铅压电陶瓷,研究了CuO掺杂对BCZT45陶瓷微观形貌、相结构、介电和压电性能的影响。X射线衍射(XRD)结果表明所有陶瓷均形成了钙钛矿结构,Cu2+固溶进入BCZT45晶格,Cu2+部分取代Ti4+引起晶格畸变。加入CuO改善了BCZT45陶瓷的烧结性能,降低了烧结温度,使陶瓷在1350℃即可烧结,提高了陶瓷密度。随着CuO含量的增加,陶瓷的介温曲线向低温方向移动。掺杂少量CuO后,BCZT45陶瓷的压电常数增大,随着CuO掺杂量的增加又急剧降低。掺杂CuO含量为0.25mol%的BCZT45陶瓷具有最好的电学性能:压电常数d33=340pC/N,室温介电常数εr=3147,介电损耗tanδ=0.025。     

0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5,Ti0.5)O3（1-x）(Ni51.5Mn25Ga23.5)x固溶体系磁电性能研究

采用传统的固相烧结法合成了0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5,Ti0.5)O3(1-x)(Ni51.5Mn25Ga23.5)x复合体系陶瓷。XRD结果表明,随着Ni51.5Mn25Ga23.5(NMG)掺入,Ni51.5Mn25Ga23.5先溶于0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5,Ti0.5)O3中,后NMG量超过5%不溶于复合体系中,使得0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5,Ti0.5)O3的峰位向右偏移;铁电性能测试结果表明,0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5,Ti0.5)O3(1-x)(Ni51.5Mn25Ga23.5)x复合体系陶瓷随着Ni51.5Mn25Ga23.5的掺入量的增加矫顽场E先降低后增加,剩余极化强度Pr逐渐降低,这与XRD的测试结果相一致;磁性测试结果表明,0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5,Ti0.5)O3(1-x)(Ni51.5Mn25Ga23.5)x随着Ni51.5Mn25Ga23.5掺入量的增加,以独立相析出在复合体系中,剩余磁化强度Mr逐渐增大。     

(Gd0.8Ca0.2)2Ce2O6.6陶瓷的制备及热导率

以Gd2O3、CeO2和CaO为原料,采用固相反应法制备(Gd0.8Ca0.2)2Ce2O6.6陶瓷材料。用X射线衍射(XRD)技术和扫描电镜(SEM)研究样品的相组成和微观组织,用激光脉冲法测试样品的热扩散系数。结果表明,所制备的样品具有单一的萤石结构,组织致密且晶界清晰,其在800℃的热导率仅为YSZ陶瓷的89%,较低热导率表明该材料有潜力用作新型热障涂层用陶瓷材料。     

氧化铝掺杂对Ba0.6Sr0.4(Zr0.2Ti0.8)O3陶瓷介电性能的影响

Zr4+取代Ti4+的Ba0.6Sr0.4(Zr0.2Ti0.8)O3固溶体在降低介电常数的同时,保持了BST固溶体优异的可调性。为降低BST材料的介电损耗和介电常数,以氧化铝为改性剂对Ba0.6Sr0.4(Zr0.2Ti0.8)O3材料(BSZT材料)进行了掺杂。随着氧化铝掺杂质量分数从1%到10%增加,BSZT材料的介电常数从5000降低到了1550(100kHz),介电损耗降低到0.001(100kHz)以下,而材料的介电可调性保持在35%左右(1.5kV/mm)。X射线衍射图谱表明,烧结后得到的BSZT材料具有典型的钙钛矿结构。扫描电子显微镜观察表明,氧化铝的掺杂使得陶瓷致密度较高,晶粒均匀。     

Electrochemical properties of LiNi0.8Co0.2?xAlxO2 (0≤x≤0.1) cathode particles prepared by spray pyrolysis from the spray solutions with and without organic additives

Fine-sized LiNi_0.8Co_0.2−xAl_xO₂ (0≤x≤0.1) cathode particles were prepared by spray pyrolysis from the spray solutions with and without organic additives. Citric acid, ethylene glycol, and Drying Control Chemical Additive (DCCA) were used as organic additives and improved the morphologies and electrochemical properties of the cathode particles. The LiNi_0.8Co_0.2−xAl_xO₂ (0≤x≤0.1) cathode particles obtained from the spray solutions with organic additives were of micro size and had slightly aggregated morphologies. The initial discharge capacities of the LiNi_0.8Co_0.2−xAl_xO₂ (0≤x≤0.1) cathode particles obtained from the spray solutions without organic additive changed from 169 mAhg⁻¹ to 190 mAhg⁻¹ when the x changed from 0 to 0.1. However, the initial discharge capacities of the cathode particles obtained from the spray solutions with organic additives changed from 196 mAhg⁻¹ to 218 mAhg⁻¹. The initial discharge capacity of the LiNi_0.8Co_0.15Al_0.05O₂ cathode particles obtained from the spray solution with organic additives was maintained after the 20th cycle at a current density of 0.1 C.     

Al0.5FeCoCrNi(Si0.2,Ti0.5)高熵合金的高温氧化性能

采用真空电弧炉熔炼制备了Al0.5FeCoCrNi,Al0.5FeCoCrNiSi0.2和Al0.5FeCoCrNiTi0.5高熵合金(下标均表示摩尔比)。研究了三种高熵合金在900℃空气中的抗氧化性能,并用带有能谱仪的扫描电镜和X射线衍射仪对不同成分高熵合金氧化层的形貌、成分和结构进行了对比分析。结果表明,三种高熵合金在900℃下均属于抗氧化级。Al0.5FeCoCrNi合金和Al0.5FeCoCrNiSi0.2合金的氧化增重曲线相似,Al0.5FeCoCrNiTi0.5高熵合金的氧化增重速率较大。Al0.5FeCoCrNi,Al0.5FeCoCrNiSi0.2高熵合金表面均生成Cr2O3氧化物,内部均生成少量AlN颗粒;Al0.5-FeCoCrNiTi0.5高熵合金氧化产物为CoFe2O4尖晶石氧化物及富含钛和铁的复杂氧化物,内部产生少量氮化物颗粒。     

(Sn1-xZnx)57(In0.78Bi0.22)43低熔点无铅焊料的微观结构表征(英文)

为了寻求一种应用于三维集成电路低温焊接的无铅焊料，基于多组元混合的概念设计并表征(Sn_1-xZn_x)₅₇-(In_0.78Bi_0.22)₄₃ (x=0.10,0.15,0.20，摩尔分数，%)四元合金。采用扫描电子显微镜、X射线衍射仪和差示扫描量热仪研究合金的显微组织、热性能和润湿性。结果表明，合金由金属间化合物BiIn₂、In_0.2Sn_0.8和富Zn固溶体组成。随着Zn添加量的增加，BiIn₂和富Zn相的体积分数增加。合金的熔点低至70℃，源自低熔点金属间化合物In_0.2Sn_0.8和BiIn₂的形成；合金具有良好的润湿性，润湿角约为40°。在合金和Cu板的界面结合处形成一种薄而坚韧的Cu₅Zn₈层，提高焊点可靠性。研究表明，通过多组元混合概念设计合金可以有效提高...     

Combinatorial approach to the growth of α-(Al1 − x,Crx)2O3 solid solution strengthened thin films by reactive r.f. magnetron sputtering

The development of new coatings with superior functionalities for high performance cutting tools is a key challenge in manufacturing. In this context, the synthesis of aluminium oxide and derivative oxide thin films is attracting large scientific and technical interests. The present paper addresses fundamental materials science-based aspects of the physical vapour deposition (PVD) growth of Al-Cr-O thin films at a substrate temperature of 500 °C. A combinatorial experimental approach was chosen to describe the growth and microstructure evolution of Al-Cr-O thin films by means of reactive r.f. magnetron sputtering. A segmented target consisting of two half plates of Al and Cr was used for the deposition carried out under stationary conditions in a laboratory-scale PVD coater. Opposite to the cathode five substrate samples were placed in a line. The r.f. cathode power was set to 500 W and the r.f. substrate bias was set to − 100 V. The total gas pressure was kept constant at 0.4 Pa for all experiments with a fixed ratio of oxygen to argon gas flow. Detailed results on the coatings composition, constitution, microstructure and properties as a function of the elemental composition are presented. X-Ray Diffraction (XRD), X-Ray Reflection (XRR), Transmission Electron Microscopy (TEM) and Electron Probe Microanalysis (EPMA) studies prove the growth of nanocrystalline, stoichiometric, metastable corundum-like solid solution strengthened α-(Al_1 − x,Cr_x)₂O₃ thin films with a high degree of crystallinity, grain sizes between 27 ± 6 nm (in the case of Al-rich coatings) and 44 ± 17 nm (in the case of Cr-rich coatings), Vickers micro hardness values up to 2620 ± 80 HV0.05 and thin film densities between 4.00 g/cm³ (in the case of Al-rich coatings) and 4.86 g/cm³ (in the case of Cr-rich coatings).     

Mn1-xZnxFe2O4 (0≤x≤1)纳米粉体的模板辅助溶胶凝胶法制备及其磁性能研究

通过模板辅助溶胶-凝胶法制备了一系列的Mn_1-xZn_xFe₂O₄(0≤x≤1,步长为0.2)纳米粉体。利用XRD和VSM对材料的物相和磁性能进行了表征,主要研究了Mn_1-xZn_xFe₂O₄分子式中Zn含量的变化对样品的微观结构和磁性能的影响。实验结果表明,具有不同Zn含量的Mn_1-xZn_xFe₂O₄样品均为尖晶石结构;随着Zn含量的增加,样品的晶面间距d、平均晶粒尺寸D、饱和磁化强度M_s和居里温度T_c都呈现出下降的趋势,而样品的矫顽力H_c则呈现出先升高后降低的趋势。分析认为,M_s的下降可以用Yafet-Kittel倾角理论解释,T_c的降低归因于晶格中反铁磁性耦合的降低,而H_c的变化则主要是由于材料的磁晶各向异性常数K₁的变化引起的。