Bi1.7Pb0.3Sr2Ca2Cu3O10多晶制备工艺对其电学性能影响的研究

采用溶胶-凝胶法成功制备了Bi1.7Pb0.3Sr2Ca2Cu3O10(BPSCCO)粉末,通过优化制备工艺获得了电学性能优良,转变温度在114 K左右的Bi1.7Pb0.3Sr2Ca2Cu3O10多晶靶材.利用X射线衍射仪测试了样品的物相和结构,并利用四探针法测试了靶材的电阻-温度曲线.对比了不同螯合剂对溶胶-凝胶法制备BPSCCO多晶的影响,发现以葡萄糖酸为螯合剂克服了传统工艺周期长、pH难调控的缺点.在此基础上,探究了热处理工艺对Bi1.7Pb0.3Sr2Ca2Cu3O10多晶电学性能的影响,得到了其最适预烧温度(600 ～ 700℃)、烧结温度(820～830℃)及烧结时间(48 h).     

Crystallization kinetic studies on Bi1.75Pb0.25Sr2Ca2Cu3-xSnxOδ glass-ceramic by using non-isothermal technique

The Sn substituted Bi_1.75Pb_0.25Sr₂Ca₂Cu_3-xSnxO_δ glass ceramic (where x = 0, 0.1, 0.3, and 0.5) samples were prepared by the melt-quenching method. Crystallization kinetic studies of the samples were conducted using the differential thermal analysis (DTA). The oxidation behavior of the samples was also analyzed using the thermogravimetry analysis (TG). The DTA curves were registered with different heating rates (5, 10, 15, and 20 Kmin^? 1) up to 1200 ± 0.5 K. The crystallization results were analyzed, and activation energy of crystallization process as well as the crystallization mechanisms and the effect of Sn substitution on powder glass ceramic were characterized. The glass transition temperature (T_g), the first crystallization peak temperature (T_x1) and the second crystallization peak temperature (T_x2) values were obtained as 713.0 ± 0.5–746.6 ± 0.5, 731.0 ± 0.5–760.8 ± 0.5 and 789.0 ± 0.5–820.1 ± 0.5 K, respectively. The activation energy (E_a) of crystallization was estimated from DTA results to be about 332.8 ± 0.1, 358.0 ± 0.1, 353.1 ± 0.1 and 348.9 ± 0.1 kJ/mol for x = 0, 0.1, 0.3 and 0.5, respectively, by using the Kissinger method. The Avrami parameter (n) values calculated at different Sn ratio from DTA results were found to be between 1.70 ± 0.01 and 2.57 ± 0.01, results reflect the growth of small particle with a decreasing nucleation rate.     

Bi precipitates in Na2O–B2O3 glasses

Bi particles of different sizes were produced in Na₂O–B₂O₃ glasses by melt quenching and heat treatment technique. Melting temperature of Bi particles was measured by differential scanning calorimetry and X-ray diffraction. Measured melting temperatures of Bi particles are lower than bulk Bi melting temperature. Results of transmission electron microscopy were analyzed for the dependence of melting temperature on particle radius. The pressure and surface energy effect on melting temperature is estimated. The melting behavior of Bi particles in Na₂O–B₂O₃ glasses depends on the difference in the interfacial energies between the solid particle/glass and liquid particle/glass, and liquid particle/glass, σ_sm−σ_lm, which is estimated to be 255×10⁻³ J m⁻².     

Li(Na,K)Ba(Sr,Ca)B9O15∶Eu3+荧光粉的制备及发光性能

采用高温固相法在空气气氛下合成了一系列Eu³⁺掺杂硼酸盐基质荧光粉。用X射线衍射、荧光光谱以及色坐标等手段对荧光粉的晶相和发光性能进行表征。通过LiBaB₉O₁₅中的碱金属以及碱土金属之间的相互取代,研究了基质组成的改变对荧光粉发光性能的影响。结果表明,在Li(Na,K)Ba(Sr,Ca)B₉O₁₅∶0.07Eu³⁺系列荧光粉中,LiSrB₉O₁₅∶0.07Eu³⁺荧光粉的发光强度最强。考察了煅烧温度、保温时间和Eu³⁺掺杂量对LiSrB₉O₁₅∶Eu³⁺荧光粉晶相和发光性能的影响,煅烧温度为750 ℃,保温时间为1~5 h时,样品的结晶性均良好。Eu³⁺掺杂量为0.52时,LiSrB₉O₁₅∶Eu³⁺荧光粉的发光强度最强。当x≥0.42(x=0.42,0.47,0.52,0.57)时,LiSrB₉O₁₅∶xEu³⁺色坐标均接近标准红光(0.67,0.33)。比较了LiSrB₉O₁₅∶xEu³⁺(x=0.02~0.57)荧光粉的611 nm(⁵D₀→⁷F₂)和586 nm(⁵D₀→⁷F₁)处发射峰相对强度比值R,R值变化不大,说明多数Eu³⁺在晶格中处于非反演对称中心的格位;比较了LiSrB₉O₁₅∶0.52Eu³⁺荧光粉和商用Y₂O₃∶Eu³⁺荧光粉的发光特性,在260 nm波长激发下,LiSrB₉O₁₅∶0.52Eu³⁺荧光粉的发光强度弱于Y₂O₃∶Eu³⁺荧光粉;在362 nm和394 nm波长激发下,LiSrB₉O₁₅∶0.52Eu³⁺荧光粉的发光强度强于Y₂O₃∶Eu³⁺荧光粉。     

溶胶-凝胶法制备Ca0.4Sr0.6Bi4Ti4O15细晶陶瓷

采用凝胶预碳化处理工艺制备了颗粒粒径较小,无硬团聚的Ca0.4Sr0.6Bi4Ti4O15纳米粉体,以Ca0.4Sr0.6Bi4Ti4O15非晶团簇粉体为陶瓷素坯的原料,同组分高浓度的Ca0.4Sr0.6Bi4Ti4O15溶胶为粘结剂,制备了Ca0.4Sr0.6Bi4Ti4O15细晶陶瓷,研究了Ca0.4Sr0.6Bi4Ti4O15粉体的相结构和微观形貌以及陶瓷的显微结构和铁电性能.实验结果表明:700 ℃焙烧粉体呈现为非晶团簇,800 ℃焙烧粉体形成了纯层状钙钛矿结构,粒径在100～150 nm之间,无硬团聚;950 ℃烧结的Ca0.4Sr0.6Bi4Ti4O15细晶陶瓷结构致密,晶粒尺寸在0.2～0.5 μm之间,其铁电性能优良,剩余极化Pr=12.5 μC/cm2,矫顽场强Ec=50 kV/cm.     

A3BGa3Si2O14(A=Ca,Sr;B=Nb,Ta)晶体研究进展

介绍了一类性能优异、结构有序的新型材料--A3BGa3Si2O14(A=Ca,Sr;B=Nb,Ta)单晶,总结了其研究进展,并对该类晶体的生长、结构、热学、光学和压电性能进行了描述.     

光学浮区法生长Bi2Sr(Ca)2Co2Oy晶体及电输运性质研究

采用光学浮区法生长了层状过渡金属氧化物Bi2Sr2-xCazCo2Oy(x=0,2)晶体.通过XRD,SEM和TEM结构表征,表明了生长的晶体为层状晶体,并确定了晶体生长的方向垂直与c轴.研究了晶体的热电性能,包括Bi2Ca2Co2Oy和Bi2Sr2Co2Oy晶体ab面的Seeback系数和电阻率,表明了Bi2Ca2Co2Oy具有较好的热电势和电导,并分析了电输运性能与晶体失配结构的关系.     

Bi2O3掺杂Sr0.92Ca0.08TiO3基陶瓷结构与介电性能的研究

通过固相反应法以Ca2+、Bi3+取代Sr2+制备出Sr0.92-1.5xBixCa0.08 TiO3(0.155≤x≤0.195)固溶体,同时加入固定量的MnCO3和ZnO作为改性剂和助烧剂,并通过XRD衍射仪、SEM扫描电镜和LCR分析仪对样品的结构和介电性能进行分析.结果 表明,当x≥0.165时陶瓷样品中出现第二相;随着Bi3+含量的增加,介电常数先增大,后减小,且介质损耗先减小后增大.当x=0.16时,得到介电常数ε=1 153、介质损耗tgδ1KHz=3.5×10-4、绝缘强度Eb=9.37 kV/mm的高介低损耗的高压电容器陶瓷介质材料.     

Pb(Zn,Nb)O3-(Pb(Zn,Ti)O3)1-x(LaySr1-y MnO3)x 固溶体系磁电特性研究

采用常规陶瓷制备工艺制备了xLaySr(1-y)MnO3+(1-x) [0.2PbZn0.5Yb0.5O3-0.8Pb0.33Zr0.67TiO3](x=0.025、0.05、0.075、0.1、0.15、0.2,y=0.7、0.9)三元体系陶瓷,系统研究了不同成分LSMO掺杂对FZN-PZT磁学及电学性能影响.结果表明,掺入不同比例的LSMO均溶解入PZN-FZT晶格,导致PZN-PZT峰位偏移;随着LSMO掺杂量的提高,陶瓷的矫顽场E及剩余极化强度Pr降低;原本分别呈现铁磁性和反铁磁性的LyS(1-y) MO3(y=0.7、0.9)磁性消失;随着LMSO掺杂量的提高,晶粒尺寸变大.     

Structure of a Cu(II)-containing peptide,diaquo-gly-l-tyr Cu(II) dihydrate, [Cu(C11N2O4H13)(H2O)2·2H2O

The structure of the Cu(II) complex of gly-l-tyr [Cu(C₁₁N₂O₄H₁₃) (H₂O)₂]·2H₂O has been solved by X-ray diffraction methods. The compound crystallizes in the orthorhombic space groupP2₁2₁2₁ witha=11.970(2) Å,b=12.485(2) Å andc=10.418(3) Å, respectively, (MoK)=0.710 Å,D _c =1.59 Mgm^–3,D _m =1.59 Mgm^–3, finalR=0.04. The structure was solved by heavy atom (Cu) phased Fourier and refined by full-matrix least squares methods. The coordination geometry of the ligand around the Cu(II) ion has been established as a distorted tetragonal pyramid. The peptide molecule behaves as a tridentate ligand via its amino (N2), amido (N1) nitrogens and carboxyl (O2) oxygens. The peptide nitrogen is found to be deprotonated.     

Computer simulation of the self-assembly of crystal structures of zeolites Ca64(Sr,K,Ba)48(Cu12(O,Cl))4[Si192Al192O786](H2O) n (tschoertnerite, TSC, V = 31 614 Å3) and Ca2K2[Al6Si6O24](H2O)10 (willhendersonite, cha, V = 804 Å3) from template nanocluster precursors K48 and K12

The self-assembly of zeolites Ca₆₄(Sr,K,Ba)₄₈(Cu₁₂(O,Cl))₄[Si₁₉₂Al₁₉₂ O₇₈₆](H₂O) _n (tschoertnerite, TSC-type framework, V = 31614 ų) and Ca₂K₂[Al₆Si₆O₂₄] (H₂O)₁₀ (willhendersonite, CHA-type framework, V = 804 ų), which form paragenetic associations, has been simulated using computational methods (TOPOS program package). A new method for analyzing zeolites of any complexity has been used, which is based on the complete expansion of the three-dimensional structural graph (3D factor graph) in tiles and the selection of nonintersecting tiles forming a packing. The code of self-assembly of 3D structures from complementary linked nanocluster precursors is reconstructed: primary chain → microlayer → microframework. A supracluster precursor K48 with the symmetry $\bar 4$ 3m, formed of four K12 clusters corresponding to the t-hpr tile, is established for TSC. The K48 cluster contains Ca template cations, which stabilize its local region in the stages of K12 → K24 → K48 self-assembly. Bifurcations of evolution paths (structural branching points) during the self-assembly of TSC and CHA microframeworks are established in the stage of formation of the K24 supracluster from invariant templated K12 clusters. The models under consideration explain the 100% localization of B = Ca cations, which play the role of templates, and the 50% occupation of the positions of K, Sr, and Ba spacer cations (in TSC) and K spacer cations (in CHA).     

Ionic conductivity of Bi12(V,Bi)O20 + δ single crystal (δ = 0.27) with a sillenite-type structure

The ionic conductivity of nonstoichiometric Bi₁₂(V_0.89Bi_0.03)O_20.27 single crystal with a sillenite-type structure has been investigated by impedance spectroscopy; its conductivity at 673 K is 2 × 10^?3 S/cm, which is about two orders of magnitude higher than the conductivity of oxide superionic conductor single crystal Zr_0.88Y_0.12O_1.94. As follows from crystallochemical analysis, ion transport in Bi₁₂(V_0.89Bi_0.03)O_20.27 is due to additional O^2? ions, which arise due to oxygen nonstoichiometry.     

Physical Properties of Vanadium Oxide Bronzes β-A0.33V2O5 (A = Ca and Sr)

Abstract

The vanadium bronzes.β-A_0.33V₂O₅(A= Ca and Sr) have been synthesized, and their electromagnetic properties investigated. They show phase transitions at 150K and 170K, respectively, accompanying with anomalies in the magnetic susceptibility and resistivity curves. These transitions are of charge order type. Below the transition temperature the magnetic susceptibility showed low dimensional behavior in both compounds, especially spin gap behavior in Sr_0.33V₂O₅. Such behavior is closely related to the crystal structure characteristic of the vanadium β-bronzes and a manner of ordering for magnetic V⁴⁺ ions at the transition.     

Iodine Intercalation of Bi2Sr2Ca(n−1)CunOy(N=2,3) Superconductors by Using Reactants I2 or FeI2

Abstract

The change of superconductivity induced by intercalation is very interesting We have investigated on intercalation into Bi2212 single crystal and Bi2223 polycrystalline superconductors using FeI₂ or I₂ as reactant. The iodine intercalation by using FeI₂ as a reactant into Bi2223 phase is reported for first time as long as we know. In iodine intercalation into Bi2212 by using FeI₂ as reactant, the critical tem T_Conset in out-of-plane measurement has suddenly decreased on X=0.95. Similar changes of T_Conset with higher X have been observed independent of directions and reactants. T_Conset of I_xBi₂Sr₂CaCu₂O_y intercalated by FeI₂ is a little lower than one of I_xBi₂Sr₂CaCu₂O_y intercalated by I₂. This is likely due to the change of hall concentration induced by reduction of host In iodine intercalation into Bi2223, the smaller change of T_Conset with increasing amount of intercalant is likely due to the number of CuO₂ planes between ntercalant layers.     

Crystal structure of tisinalite Na2(Mn,Ca)1 − x (Ti,Zr,Nb,Fe3+)[Si6O8(O,OH)10]

Crystal structure of tisinalite from the Lovozero alkaline massif (the Kola Peninsula) was established by single-crystal X-ray diffraction analysis (SYNTEX $\bar P1$ diffractometer, λMoK_α radiation, 2θ/θ scanning mode). The structure solution (SHELX97 program package, R _hkl = 0.0565, 951 independent reflections, anisotropic refinement of thermal atomic displacements) confirmed that tisinalite belongs to the lovozerite structure type (sp. gr., $\bar P1$ , a = 10.036(5) Å, c = 12.876(9) Å, Z = 3). The difference between the structure of tisinalite and the structures of the minerals of the lovozerite group established earlier consists in the nature of the occupancy of both cation and anion positions.     

La2Ca1-xSrxB10O19(Sr2+∶LCB)晶体的生长及光学性质

通过顶部籽晶法生长出掺5;和8;Sr2+的La2CaB10O19(LCB)晶体,ICP测得LCB晶体中Sr2+掺入量分别为1.75;和2.02;.XRD证实Sr2+的掺入对LCB晶体晶胞参数的影响较小.摇摆曲线测得Sr2+∶LCB晶体半高宽为36",表明晶体具有较高质量.Sr2+∶LCB晶体在300～2000 nm波段具有较高的透过率,紫外截止边为172 nm.拟合的色散方程符合Sr2+∶LCB晶体折射率的实验值,理论计算表明Sr2+∶LCB晶体可实现相位匹配,其最短二倍频波长小于LCB晶体.     

Synthesis and structure–property relations in xCuO–(1 − x)Bi2O3 (0.5 ⩽ x ⩽ 0.9) (C1–C5: x = 0.5, 0.6, 0.7, 0.8, 0.9) glasses

Synthesis of the xCuO–(1 ? x)Bi₂O₃ (0.5 ? x ? 0.9) (C1–C5: x = 0.5, 0.6, 0.7, 0.8, 0.9) glasses was done via nitrate–citrate gel route. Glassy phase is ascertained by XRD studies. Magnetic susceptibility results in the range 4.2–400 K show weak paramagnetic nature with exchange integrals ～0.024–0.13 eV in the glasses. The electron paramagnetic resonance (EPR) in the range 4.2–363 K shows g ≈ 2.0 and the trend of the g-matrix elements g_|| > g_⊥ > g_e for the glasses C1–C5 at 4.2 K are due to the Cu²⁺ (3d⁹) paramagnetic site in the glasses which is in a tetragonally elongated octahedron [O_1/2–CuO_4/2–O_1/2] having D_4h symmetry. IR spectroscopic results show the presence of octahedron [BiO_6/2]^3? and [CuO_6/2]^4? units and pyramidal [BiO_2/2O]^? unit in the glasses.