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本文讨论了由作者首次人工合成的新的钨青铜结构铁电单晶(K0.20Na0.20Sr0.60Ba0.20)Nb2O6全部电弹常数的测量方法和测量程序。第一次发表了该晶体的全部电弹常数及电-机耦合系数等共53个数据。绝大多数的数据是按IRE标准进行测量的。采用了(zxl)45°切片的厚度切变振动模式和(xzt)45°棒的长度扩张模式来测定弹性系数s66D和s13D。对实验过程引起的测量误差进行了讨论。
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通过制备(YBa2Cu3O7)1-x(V2O5)x(0≤x≤0.15)复合材料,获得了一系列典型的弱连接的颗粒超导体,其中以dR/dT-T关系中呈现出双峰转变为主要特征。第一峰代表晶粒的超导转变,第二峰代表颗粒系统超导长程序的形成。对于具有双峰转变的样品,其临界电流密度一致地符合ic~(1-t)n,n=1.6.这一行为与三维Josephson结网络系统的渗流行为相一致;对于不具有双峰转变的系统,临界电流密度随温度的变化尽管也可以用jc~(1-t)n描述,但是幂指数n明显地大于1.6,且随样品的不同而离散地分布。本文还对产生这种离散的原因进行探索和分析。
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使用X射线单晶衍射法测定了Bi2Pb2V2O10的结构。该晶体属三斜晶系,空间群为C11-P1,单位晶胞内化学式数Z=1,晶胞参数为:a=7.084(4)?,b=7.278(3)?,c=5.587(3)?,α=111.91(5)°,β=95.01(6)°,γ=108.86(4)°,V=245.70?3,Dx=7.35g/cm3,μ(MoKα)=678,94cm-1,F(000)=456。用Patterson函数分析及Forier技术测定了结构,对原子坐标、各向同性及各向异性热参数进行了最小二乘方修正,R=0.079。结构分析表明,Bi2Pb2V2O10的Pb原子与O原子形成八角十二面体,Bi原子与O原子形成六角多面体。两个共棱的Pb—O多面体与两个共棱的Bi—O多面体相连,并沿bc平面无限延伸。讨论了吸收的影响。最后,将Bi2Pb2VO10的结构与Pb2SO5的结构进行了比较。
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POWDER NEUTRON DIFFRACTION STUDIES OF THE CRYSTALLOGRAPHIC AND MAGNETIC STRUCTURE OF Ho2Fe9Ga8 and Ho2Fe9Ga6AI2 下载免费PDF全文
The crystallographic and magnetic structures of Ho2Fe9Ga8 and Ho2Fe9Ga6AI2 were studied by powder neutron diffraction at room temperature. The atom fractional occupancies of Ga and Al and the magnetic moments of Ho and Fe were obtained by using Rietveld analysis program. The magnetic structures of the two samples show an easy-axis anisotropy, with the Fe magnetic moment being ferrimagneticlly coupled to those of Ho. 相似文献
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用射频/直流磁控溅射法制备了CeO2/Nb2O5双层氧敏薄膜,利用X射线光电子能谱(XPS),描述并解释了单层CeO2薄膜中氧随温度变化的动力学行为,以及CeO2/Nb2O5薄膜界面对氧敏特性的影响.通过对Ce3d XPS谱的高斯拟合,计算了Ce3+浓度并给出了判定Ce4+还原的标志.结果表明,界面效应可以提高CeO2/Nb2O5薄膜中Ce4+的还原能力,使之远远高于单层CeO2薄膜,这对薄膜的氧敏特性是极为有利的.
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The crystal and magnetic structures of Nd2Fe14Si3 at room temperature were refined by Rietveld analysis of neutron-powder-diffraction data. It was found that silicon atoms occupy preferentially both 18h and 18f of Th2Zn17-type structure with occupancies 0.36 and 0.14, respectively, The Fe-Fe bond-lengths computed with the refined crystallographic parameters have optimum values, as compared with those of Nd2Fe17 compounds, which can explain well why the Curie temperature rises strongly when the unit cell volume reduces with the substitution of silicon for iron in Nd2Fe17. 相似文献
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In this work, we made five samples of SrAl2O4: Eu2+, Dy3+, the α phase and β phase SrAl2O4:Eu2+,Dy3+ powder and pellet samples, and α phase single crystal. We have measured the emission spectra of all the samples. All the emission peaks are around 520 nm, which correspond to the transition from 4f65d1(2Eg) to 4f7(8S7/2) of Eu2+ in SrAl2O4 host. The intensity of emission of the β phase is stronger than that of the α phase. We believe that it is because the Eu2+ ions have occupied the two types of sites in the α phase SrAl2O4 host and the lifetime of the transition of Eu2+ in the A site is longer than that in the B site. This result also proves that the β phase of the material is brighter than the α phase. In addition, the β phase can be achieved by quenching technique. 相似文献
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A weak ferromagnetic transition has been observed for the T'-type compound Eu1.85Ca0.15CuO4. The samples were prepared by a high pressure (5 GPa) synthesis technique. Their transition temperature occurred at 27 K. At 5 K the residual magnetization was 0.033 emu/g, the coercive force was 6.3×104 A/m and the saturation field was larger than 1.6×105 A/m. A field cooling method is proposed as a very convenient way to determine the residual magnetization and coercive force. The compound Eu1.85Ca0.15CuO4 is suggested to use as a sensor to measure the remanant field of SQUID magnetometer. 相似文献
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用固相反应法合成了名义组分为Bi1.92Pb0.32Sr2Ca1.7Mg0.3Cu3.07Ox的块状样品。X射线衍射谱(XRD)、扫描电子显微镜(SEM)和电子探计X射线分析(EDAX)结果以及块状和粉状试样的交流磁化率测量表明,样品中存在110和85K两个超导相;2223相(110K)首先在2212相(85K)晶体的晶界和外部区域生成。本文认为,最初存
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本文报道非晶态Fe13Ni67.2P4.5B15.3合金的磁化强度与温度和磁场关系的测量结果。在居里温度附近样品的磁特性符合二级相变规律,得到临界指数β=0.39±0.02,γ=1.56±0.06,δ=5.20±0.1,样品的居里温度Tc=(180.4±0.2)K。在实验误差范围内,临界指数β,γ,δ满足γ=β(δ-1)关系,在168—192K温度范围,实验数据满足二级相变的磁状态方程。当T>270K时,样品顺磁磁化率服从居里-外斯定律,由居里-外斯常数c计算出有效顺磁磁矩Peff=3.19 μB。
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