Solid state reaction synthesis and total electrical conductivity of La_(0.7)Sr_(0.3)Cr_yMn_zCo_(1-y-z)O_(3-δ)

The La0.7Sr0.3CryMnzCo(1-y-z)O3-δ samples were prepared by solid state reaction.The phases,microstructure and properties of the samples were investigated by XRD,SEM,DC four-probe method and iodometry method.The single orthorhombic phase La0.7Sr0.3CryMnzCo(1-y-z)O3-δ perovskite oxides were obtained when sintered at l350 °C for 10 h.The oxygen nonstoichiometry of the materials varied inversely with the total electronic conductivity.The sample with composition of La0.7Sr0.3Cr0.5Mn0.35 Co0.15O3-δ had the maximal total electronic conductivity and the lowest oxygen nonstoichiometry which were 22.4 S/cm and 0.040 at 850 °C,respectively.The low total electronic conductivity is related to the low relatively density of the samples directly.The activation energy of conduction changed at 550 °C,and the activation energy of conduction at high temperature(T550 °C) was higher than that at low temperature range(T550 °C).     

Preparation and characterization of La0.9Sr0.1Ga0.8Mg0.2O3–δ thin film deposited by radio frequency magnetic sputtering

La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) electrolyte materials were synthesized by the solid state reaction method.The conductivity of LSGM materials was detected by four probe method,and it was 0.08 S/cm at 850 ℃.Dense and uniform films of LSGM materials were deposited by the magnetic sputtering on substrates of Si and La0.7Sr0.3Cr0.5Mn0.5O3-δ (LSCM).The experimental results showed that the deposition rates dropped and the average grain sizes of the films enlarged with increase in the substrate temperatures.In the sputtering process,the LSGM film was deposited with preferred growth direction.After annealing,the preferred growth direction disappeared and the film surface became smoother and denser.Through observing the deposition process,deposition mechanism was proposed,which was consistent with a model of island growth.     

Synthesis and characterization of La NixCo1–xO3: Role of microstructure on magnetic properties

Perovskite-type structures with the composition La Ni x Co1–x O3(x=0.3, 0.5, 0.7) were synthesized by a modified sol-gel method. Using transitional metal elements on the lanthanum base perovskites, properties could be tuned by doping the structure. Thermogravimetric analysis(TGA) evidenced a temperature of 350 °C as the start point of the perovskite-phase formation. Scanning electron microscopy(SEM) images showed the microstructure changes(grain size) of the cobalt-doped perovskite due to composition. In addition, it was shown that magnetic properties of the samples were dependent of cobalt content; experimental results pointed to the existence of disordered spins interactions, which were more evident with the decrease of cobalt content and the existence of ferromagnetic coupling among spins of the samples. These results showed the feasibility of producing a family of compounds with the desired properties, manipulating composition and therefore the microstructure.     

Influence of the substitution of Sm, Gd, and Dy for La in La_(0.7)Sr_(0.3)MnO_3 on its magnetic and electric properties and strengthening effect on room-temperature CMR

A series of La0.7–xSmxSr0.3MnO3, La0.7–xGdxSr0.3MnO3, and La0.7–xDyxSr0.3MnO3 (x=0.00, 0.10, 0.20, 0.30) samples were prepared by the solid-state reaction method. The influence of the substitution of Sm, Gd, and Dy for La on the magnetic and electric properties and on the magnetoresistance (MR) was studied through measurements of M-T curves and ρ-T curves. The results showed that: lattice distortion in-duced by substitution of Sm, Gd, and Dy for La and extra magnetism of substitution had great influence on the magnetic and electric proper-ties of perovskite manganites; substitution of magnetic rare earth element for La was an effective way to change Curie temperature and to strengthen MR in perovskite manganites; and appropriate substitution proportion would generate large MR near room temperature.     

Influence of the substitution of Sm, Gd, and Dy for La in La0.7Sr0.3MnO3 on its magnetic and electric properties and strengthening effect on room-temperature CMR

A series of La0.7-xSmxSr0.3MnO3, La0.7-xGdxSr0.3MnO3, and La0.7-xDyxSr0.3MnO3 （x=0.00, 0.10, 0.20, 0.30） samples were prepared by the solid-state reaction method. The influence of the substitution of Sm, Gd, and Dy for La on the magnetic and electric properties and on the magnetoresistance （MR） was studied through measurements of M-T curves and p-T curves. The results showed that： lattice distortion induced by substitution of Sm, Gd, and Dy for La and extra magnetism of substitution had great influence on the magnetic and electric properties of pcrovskite manganites; substitution of magnetic rare earth element for La was an effective way to change Curie temperature and to strengthen MR in perovskite manganites; and appropriate substitution proportion would generate large MR near room temperature.     

Preparation and Long Persistence Red Luminescence of M0.2Ca0.8TiO3∶Pr3+(M=Mg2+,Sr2+,Ba2+,Zn2+)

M0.2Ca0.8TiO3∶Pr3 (M=Mg2 , Sr2 , Ba2 , Zn2 ) long persistence red phosphors were prepared by solid state reaction. The influence of the partially replacing Ca2 in CaTiO3 with Mg2 , Sr2 , Ba2 , Zn2 on the excitation spectra, the emission spectra and the long persistence properties were studied. The results suggest that certain quantity of Mg2 , Sr2 , Ba2 , Zn2 which partially replace Ca2 can enhance the luminescent intensity and prolong the afterglow persistence of the samples. The intensity of Mg0.2Ca0.8TiO3∶Pr3 is above all of the samples. Take Mg0.2Ca0.8TiO3∶Pr3 as the basic sample, the influence of Pr3 concentrations(C(Pr3 )) on the long afterglow properties were also studied. The results suggest that when the C(Pr3 ) is 0.10%(mol fraction) the intensity of the sample is the highest. The excitation spectra of all these samples show broad band spectra ranging from 300～500 nm peaking at about 342 nm. The emission spectra also exhibit a broad band peaking at 613 nm(CaTiO3∶Pr3 is 612 nm). XRD research indicates that the crystalline phases change due to the replacement of divalent metal ions.The research on the thermoluminescence spectra of Mg0.2Ca0.8TiO3∶Pr3 indicates that the peak is at 107.35 ℃ and the depth of the trap energy is about 0.852 eV.     

Magnetic Properties of La1-xSrxCoO3 （0 ≤ x ≤ 0. 5）

The measurements of temperature dependence of the magnetic susceptibility of La1-xSrxCoO3 perovskite oxides at different Sr doping （0 ≤x ≤0.5） and annealing temperature were presented. For the sample with x = 0.1, a shoulder was observed around 150 K, and a peak which is one feature of spin glass appeared around 50 K in the curve of susceptibility versus temperature. The high-temperature （250 - 420 K）susceptibility fits well with Curie-Weiss law for all samples. Weiss constant and effective magnetic moment were determined and their variations with Sr doping and oxygen annealing condition were obtained. The Weiss constant increases monotonously with Sr content for x 〉 0.2. The values of effective moments were interpreted with the spin state of cobalt ions. Studies on the susceptibilities of the samples with x = 0.2 under different preparation temperatures and annealing temperatures show that the rising of sintering temperature and annealing temperature will increase the para-ferromagnetic transition temperature, and reduce the effective moment to normal value. Our result shows that both Co^3＋ and Co^4＋ ions should be in IS state after annealing and the oxygen annealing causes the transition of Co^3＋ spin state from HS to IS.     

Influence of oxygen non-stoichiometry on physical properties of NdSr2Mn2O7±δ

Nd Sr2Mn2O7+δ compounds were synthesized by ceramic method under three different cooling conditions. The Nd Sr2Mn2O7+δ samples were characterized by powder X-ray diffraction(XRD). Oxygen non-stoichiometry data for the studied powders were determined by using gravimetric and X-ray photoelectron spectroscopy(XPS) methods. The correlation of cooling method and oxygen as non-stoichiometry was established. The electroconductivity in samples was studied by using four-point probe method, and the strong correlation with non-stoichiometry was found out. Magnetization measurements were carried out. It was found that the magnetic and transport properties of the samples were also influenced by oxygen non-stoichiometry. The evolution of the magnetic properties could be explained by the formation of magnetic clusters in the vicinity of oxygen vacancies(OV) and strong competition between the superexchange and double exchange interactions.     

Piezoelectric and upconversion emission properties of Er3+-doped 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 ceramic

In this investigation, the ferroelectric, piezoelectric properties, and upconversion(UC) emissions of Er3+-doped 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)Ti O3(BZT-BCT) were investigated. The results showed that the ferroelectric and piezoelectric performances of BZT-BCT ceramics decreased with the increment of Er doping content. Under the excitation of 980 nm light, all samples exhibited strong green UC emissions. A maximum green UC emission was observed in BZT-BCT:0.015 Er. The variation of the UC emission with Er doping content did not coincide with that of electrical properties of the ceramics. The relation between the UC emission and piezoelectric properties was discussed.     

Preparation and Electrical Transport Properties of Perovskite Oxide Ln0.5Sr0.5CoO3

The superfine powders of Ln0.5 Sr0.5 CoO3 （Ln = La, Pr, Nd, Sm, Eu） were obtained by solid state reactions. The crystal structure and electrical transport properties of samples doped with different rare earth elements as well as the forming process of the Perovskite structure were studied. The result shows that when the temperature reaches 1200 ℃, the samples will become a steady and unitary Perovskite phase by solid state reactions. The conductive behavor at low temperature is consistent with small polaron mechanism （i. e., localized electronic carriers having a thermally activated mobility）. However, the maximum of conductivity appears at about 700 ℃, and the conductivity of La0.5Sr0.5CoO3 is the biggest in the intermediate-temperature （600 - 850 ℃ ）, so it is fit for cathode material of intermediate-temperature solid oxide fuel cells.     

微波合成固体氧化物燃料电池阴极材料La1-xSrxMnO3的研究

采用微波技术合成了固体氧化物燃料电池阴极材料La1-xSrxMnO3样品，分别选择x=0.1,0.2,0.3,0.4和0.5合成了La0.9Sr0.1MnO3,La0.8Sr0.2Mn3,La0.7Sr0.3MnO3,La0.6Sr0.4MnO3和La0.5Sr0.5MnO3，用X射线衍射分析检测了样品的结构与组成，用电子扫描电镜考查了样品的形貌和粒度，电导率测量结果表明，样品的组成和烧结温度影响电导率。在系列样品中，组成为La0.7Sr0.3MnO3电导率最高；烧结温度1200℃和1300℃相比较，1300℃烧结后样品的电导率大幅度提高。     

Competition between Band Filling and Steric Effect in Ordered Double Perovskites Sr2- x Lax MnMoO6

The ordered double perovskites, Sr2-xLaxMnMoO6, were prepared by sol-gel reaction. Structural, magnetic, and electrical properties were investigated for a series of ordered double perovskites Sr2- x Lax MnMoO6 （0 ≤ x ≤ 1 ）. The compounds have a monoclinic structure （space group P21/n） and the cell volume expands monotonically with La doping. The Tc and the magnetic moment rise and the cusp-like transition temperature below which the magnetic frustration occurs shifts to high temperature as x increases. With La doping, electrical resistivity of Sr2-x LaxMnMoO6 decreases only at low doping levels （x ≤0.2）; while at high doping levels （0.8≤x ≤1）, electrical resistivity tends to increase greatly. The resuits suggest that the competition between band filling effect and steric effect coexists in the whole doping range, and the formation of ferrimagnetic interactions is not simply at the expense of antiferromagnetic interactions.     

容量型锂离子电池正极材料LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2的合成

采用共沉淀法合成Ni_(0.5)Co_(0.2)Mn_(0.3)(OH)_2前驱体,将前驱体和LiOH混合均匀后经高温煅烧合成了锂离子电池正极材料LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2,并对其进行电化学性能检测。试验表明,制备的电池在电压2.8～4.3V(vs.Li/Li+)区间内,0.1C倍率下的首次库伦效率为88.4%;在1C倍率下循环100次后,放电比容量为157.7mAh/g,容量保持率为96.6%。     

碳酸盐共沉淀法合成Li1＋xNi0.6Co0.2Mn0.2O2Fx正极材料及其电化学性能

采用碳酸盐共沉淀法合成Li1＋xNi0.6Co0.2Mn0.2O2Fx正极材料,研究了不同含量的Li、F复合掺杂对LiNi0.6Co0.2Mn0.2O2样品的晶型结构、形貌以及电化学性能的影响.研究结果表明：Li、F复合掺杂未改变LiNi0.6Co0.2Mn0.2O2样品的层状结构;掺杂后的样品颗粒细化;电化学循环性能和电极过程的可逆性明显得到提高.掺杂量x=0.06时,Li1＋xNi0.6Co0.2Mn0.2O2Fx样品的首次充放电容量分别为168,160 mA·h/g,循环50次后容量为153 mA·h/g.     

锂离子电池正极材料LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2的制备与性能研究

以自制Ni0.4Co0.2Mn0.4(OH)2前驱体和Li_2CO_3为原料,在空气气氛下采用固相烧结工艺制备了LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2锂离子电池正极材料。通过SEM和XRD等手段对材料烧结前后形貌与结构进行表征,并测试了烧结后锂离子电池正极材料的电化学性能。结果表明,Ni0.4Co0.2Mn0.4(OH)2前驱体具有良好的片状嵌入结构,且烧结制备的LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2正极材料混排因子c/a=4.967 3,阳离子混排因子I(003)/I(104)=1.25、I(006+102)/I(101)=0.333、I(018)/I(110)=0.87,表明LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2具有良好的层状结构。在2.5~4.6V、0.2C和0.5C下,LiNi_(0.4)Co_(0.2)Mn_(0.4)O_2正极材料的首次放电比容量分别为166和154mAh/g,循环80次后容量分别保持为111和100mAh/g,具有良好的电化学性能。     

Magnetic and Transport Properties of Bi0.5Ca0.5-xLaxFe0.3Mn0.7O3 (x=0, 0.05, 0.10, 0.15, 0.20, 0.25) Prepared by Molten Salt Method

Polycrystallines Bi0.5Ca0.5-xLaxFe0.3Mn0.7O3(x=0, 0.05, 0.10, 0.15, 0.20, 0.25) were prepared by molten salt method and showed perovskite orthorhombic structure with space group Pnma. The magnetic measurements in-dicate that the compounds exhibit antiferromagnetic behavior in a temperature range of 4-300K. The measurements of transport properties suggest that the substitution of La for Ca enhanced the conductivity, and a kink appeared on the curve of temperature dependence of resistivity at 275 K, which is related to the spin-reorientation in the samples.     

Effect of annealing temperature on microstructure and electrochemical performance of La0.75Mg0.25Ni3.5Co0.2 hydrogen storage electrode alloy

To improve the cyclic stability of La-Mg-Ni system alloy, as-cast La0.75Mg0.25Ni3.5Co0.2 alloy was annealed at 1123, 1223, and 1323 K for 10 h in 0.3 MPa argon. The microstructure and electrochemical performance of different annealed alloys were investigated systematically by X-Ray Diffraction （XRD）, Scanning Electron Microscopy （SEM）, X-Ray Photoelectron Spectroscopy （XPS）, and electrochemical experiments. The results obtained by XRD and SEM showed that the as-cast and annealed （1123 K） alloys had multiphase structure containing LaNis, （La, Mg）2（Ni, Co）7 and few LaNi2 phases. When annealing temperatures approached 1223 and 1323 K, LaNi2 phase disappeared. The annealed alloys at 1223 and 1323 K were composed of LaNi5, （La, Mg）2（Ni, Co）7 and （La, Mg）（Ni, Co）3 phases. With increasing annealing temperature, the maximum discharge capacity of the alloy decreased monotonously, but the cyclic stability was improved owing to structure homogeneity and grain growth after annealing, as well as the enhancement of anti-oxidation/corrosion ability and the suppression of pulverization during cycling in KOH electrolyte.     

Luminescence properties of Mn2） ions doped Lu2CaMg2Si3O1） garnet phosphors

Yttrium aluminum garnet structure phosphors Lu2CaMg2Si3O12:Mn2+ were synthesized by conventional high temperature solid-state reaction in reductive atmosphere. The structure and optical properties of samples were characterized by application of powder X-ray diffraction (XRD) and photoluminescence spectroscopy. Results of X-ray diffraction (XRD) analysis showed that the phosphors mainly presented garnet structure with a few weak peaks of impurity phases. Lu2-xCaMg2Si3O12:xMn2+ (x=0.01-0.8) phosphors showed a broad emission band peaking at around 590 nm under ultraviolet (UV) light of 408 nm when Mn2+ concentration was less than 0.08 mol. With an increase in the Mn2+ concentration (above 0.08), another broad emission band peaking at 720 nm besides 590 nm was observed, which may be due to manganese ion having different valence and occupying different host lattice. The critical quenching concentrations of manganese ion in the wavelength of 590 and 720 nm were about 0.06 and 0.2 mol, respectively. With 408 nm excitation wavelength, emission color of the samples had a red shift trend as the Mn2+ concentration increased. All the results indicated that the Lu2CaMg2Si3O12:Mn2+ phosphors could be applicable to n-UV based white LEDs.     

M型稀土永磁铁氧体的微观结构与磁性研究

采用粉末冶金工艺,结合CaSiO_3与BBSS助熔剂的复合掺杂技术,制备了M型稀土永磁铁氧体。用费氏粒度仪测量成形用颗粒料的平均粒度,用SEM、EDS、XRD、永磁铁氧体测量仪等分析测试样品的显微结构、物相、断面形貌及磁学性能,用浮力法测定样品表观密度。结果表明:CaSiO_3与BBSS助熔剂的复合掺杂促进了M型稀土永磁铁氧体晶粒的均匀生长,改善了产品的取向度,从而明显改善了产品的磁性能及内禀矫顽力HCJ的温度系数β(HCJ),但铁氧体的居里温度略为下降。对Ca_(0.45)La_(0.45)Sr_(0.1)Fe_(10.3)Co_(0.3)O_(19-δ)预烧料,细粉碎时添加0.7%的CaSiO_3、0.4%的助熔剂BBSS(均为质量分数),经成形、烧结之后,可获得Br为455 m T,HCJ为412 k A/m,M*值为6 275.3、Hk/HCJ为95.8%的M型高性能稀土永磁铁氧体。