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1.
 利用X射线衍射分析和Rietveld结构精修的方法研究了固相线下Pr1-xBa2-yCax+yCu3O7±δ体系的相关系和晶体结构。研究表明:950 ℃、空气条件下,Pr1-xBa2-yCax+yCu3O7±δ(y=0)体系系列样品总是含有两相:Pr123(PrBa2Cu3O7±δ)和BaCuO2;而且,随Ca含量的增加,杂相BaCuO2的含量也随之增加。Pr1-xBa2-yCax+yCu3O7±δ(x=0)体系y=0.1、0.2、0.3、0.4的样品都只含有Pr123单相;y=0.5的样品含有3相:Pr123、Ca2CuO3和Pr4Ca10Cu24O41。另外,Pr1-xBa2-yCax+yCu3O7±δ(x=0)系列样品(y=0.1、0.2、0.3、0.4)中Pr123相还发生了正交-四方晶系的结构转化。y=0.1和0.2的样品为正交晶系,晶胞参数分别为a=0.390 33(4)和0.389 36(1) nm,b=0.389 53(4)和0.387 73(1) nm,c=1.173 38(4) 和1.168 20(2) nm;y=0.3和0.4的样品为四方晶系,晶胞参数分别为a=b=0.387 80(0) 和0.387 67(0) nm,c=1.166 00(2) 和1.165 20(2) nm。在Pr123结构中,Ba离子可以被Pr离子代替,但不能被Ca离子所代替。Ca离子占据部分Pr离子的位置。在Pr1-xBa2-yCax+yCu3O7±δ(x=0)体系中Pr、Ba和Ca离子间的相互替代中,离子半径比化学性质起到了更大的作用。在950 ℃、空气条件下,Ca离子在Pr1-xBa2-yCax+yCu3O7±δ体系中的最大溶解量是当x=0时,y≤0.4。  相似文献   

2.
 采用金刚石压砧高压装置(DAC),对具有Cu—O链结构的Ca2CuO3的多晶粉末样品进行了高压同步辐射能散X射线衍射实验。实验结果表明,在0~34 GPa压力范围内,Ca2CuO3晶体没有发生结构相变,用Birch-Murnaghan状态方程拟合,得到在压力导数B′0=4时,零压体弹模量B0=165.4±1.8 GPa。  相似文献   

3.
 利用“顶角氧掺杂”机制,即以二价氧部分替代顶角一价氯,用Ag2O做氧源,在高温高压下制备了单相的Ca3Cu2O4+δCl2-y样品。X射线衍射分析发现,随着Ag2O含量的增加,Ca3Cu2O4+δCl2-y样品的晶格常数a逐渐变小,c逐渐增大,体现了空穴掺杂的本质。进行了电阻率和磁化率测量,没有发现超导性,可能是空穴载流子没有达到合适的浓度所致。  相似文献   

4.
 采用溶胶凝胶法制备了纳米Ti1-xCexO2系列样品。利用X射线衍射(XRD)、透射电子显微镜(TEM)、高分辨电子显微镜(HRTEM)对纳米Ti1-xCexO2系列样品颗粒尺寸、形貌以及固溶区范围和物相组成进行了研究;同时,采用Rietveld结构精修的方法研究了Ce的不同掺杂量对TiO2晶体结构的影响。实验结果表明,Ce掺杂TiO2能够形成Ti1-xCexO2固溶体,Ti1-xCexO2的固溶区范围在x=0~0.06之间,Ti1-xCexO2的晶粒度为5~10 nm,平均颗粒粒度约35 nm,且粒度均匀。  相似文献   

5.
 采用高压下的固相反应方法,成功地合成了具有空间群I4/mmm的理想三层结构化合物Ca4Mn3O10。用电子显微学方法对此结构进行了研究,并提出了近似的结构模型。基于提出的模型,进行了电子衍射图和高分辨像的模拟,并与实验结果进行了比较。  相似文献   

6.
 采用X射线粉末衍射和同步辐射能散X射线衍射技术,对LiB3O5(LBO)晶体进行了压致非晶化相变的研究,压力达45.1 GPa。实验结果表明,LBO存在两个中间相变,压力分别为5 GPa和15.8 GPa。而当压力增加到25~31.6 GPa时,LBO出现非晶态,这个非晶化相变是不可逆的。  相似文献   

7.
 本文研究了冷压(2.2~5.2 GPa)与热压(2.2 GPa,2.50~950 ℃)对YBa2Cu3O7-δ的正交→四方相转变区和超导电性的影响。冷压保持其正交结构,但破坏了超导性,在98 K(失超点)到室温呈半导体特性,再在空气中烧结,可恢复液氮温区的零电阻状态。以Cu锅密封样品,热压处理至950 ℃,不发生Cu的析出。热压处理后,98 K(失超点)到室温呈半导体特性,再经通氧烧结,于86 K出现零电阻。热压处理过程,从450~950 ℃为正交→四方转变区。950 ℃为转变结束温度,大大高于氧气、空气、氮气、真空状态的温度。400 ℃附近为起始转变温度,低于氮气、氧气气氛的温度。因此相变区加宽。T0-t结束温度升高,与Cu锅的抑制还原作用有密切关系。如降低高压淬火速率(<<102 ℃/s),或随后辅以氧气氛中的后处理,将有利于获得既有高密度又有高Tc的YBa2Cu3O7-δ超导体。  相似文献   

8.
 通过B2O3与Mg和Li3N分别在不同温度压力条件下的反应,用X射线方法研究了生成物的物相。当采用Mg与B2O3为原料时,其产物是Mg3B2O6;用Li3N与B2O3反应时,产物中除了Li3BO3,还有立方氮化硼(cBN)生成。这表明,当原料中含有相同数量B2O3时,用Mg和Li3N分别作触媒合成立方氮化硼,将得到不同的结果。  相似文献   

9.
 本文利用X射线粉末衍射和位敏探测技术,研究了R2Fe4/3W2/3O7(R=Er、Yb、Dy)化合物经高温高压处理后的变化情况。在3.7 GPa,1 200 ℃条件下,六方相R2Fe4/3W2/3O7化合物按两种方式分解,而直接由R2O3,Fe2O3和WO3原料出发,经上述同样的高温高压条件合成所得的产物与六方相高温高压分解产物相同,均为R2WO6、RFeO3、WO3和Fe2O3的多相聚合物。同时给出了R2Fe4/3W2/3O7六方相高温高压下的稳定区范围。  相似文献   

10.
在对光控热电效应开关进行理论分析的基础上,木文提出用YBa2Cu3Ox薄膜制作光控开关,并测试了在液氮温度下薄膜开关在不同激光波长下的特征参数,测试的最好结果是响应度Rv(632.8nm,10kHz,1Hz)为217V/W,归一化探测率D*(632.8nm,10kHz,1Hz)为2.3×1011cm.Hz1/2/W,响应时间τ为0.21ms.  相似文献   

11.
The effects of whisker content, sample holding time, and differential scanning calorimetry (DSC) analysis of the crystal structure of polypropylene/Mg 2 B 2 O 5 whisker composites were investigated. DSC shows a double melting peak, T 1 at about 151°C and T 2 at about 166°C. Detailed analysis of wide angle X-ray diffraction (WAXD) shows that a γ phase may exist in the polypropylene/Mg 2 B 2 O 5 composite. The experimental results also show that the crystal structure according to MPLT (melting peak at low temperature) was more perfect and the crystallinity according to MPLT increased with increasing whisker content. The sample holding time at room temperature following injection molding had a significant effect on the number of γ -crystal nuclei.  相似文献   

12.
采用加热回流技术制备了系列CexZr1-xO2(0.25≤x≤1)固溶体,通过N2物理吸附、XRD、Raman光谱、UV-Vis漫反射光谱表征了不同铈锆组成的铈锆复合氧化物结构对储氧性能的影响.结果表明,在铈锆组成比不同的样品之间,结构性质相差较大,随着载体中ZrO2 mol%的增加,载体结构从相对的有序经无序再回到相对的有序.Ce0.4Zr0.6O2样品具有最高的储氧性能,而Ce0.25Zr0.75O2样品具有较高的热稳定性.  相似文献   

13.
The bond geometry of the (2 × 1)-2O-p2mg overlayer on Co(10 0) was determined by analyzing low-energy electron diffraction (LEED) intensity data. Oxygen occupies the three-fold coordinated hcp site along the densely packed rows on the unreconstructed surface. The O atoms are attached to two atoms in the first Co layer and to one Co atom in the second layer. The strong interaction between O and Co is indicated by the bond lengths of 1.83 ± 0.10 Å and 1.99 ± 0.10 Å to the top-layer Co and the Co atoms in the second layer, respectively. The most striking result of our work is that oxygen adsorption causes a marked expansion (by 25%) of the first Co layer spacing (0.90 Å) with respect to the bulk value of 0.72 Å. This strong expansion might offer diffusion channels for O atoms to penetrate further into the subsurface region.  相似文献   

14.
The potential of single crystals K5Li2LnF10, for applications as VUV excited phosphors has been examined. The crystals were doped with lanthanide ions (Ce3+–Nd3+) with concentrations up to 100 at%. The self-quenching of luminescence is strongly reduced in this material. Luminescence spectra in the 50,000–10,000 cm−1 range and excitation spectra in the 40,000–250,000 cm−1 spectral range have been recorded at room and low temperature. Intense visible emission has been observed for Nd3+ and Pr3+. For the Pr3+ ions strong the 1S01I6 transition has been recorded only for concentrated crystals. Efficient conversion of VUV excitation to UV–VIS emission was observed in crystals doped with 3 and 100 at% of cerium. In both cerium-activated crystals the lifetimes of fd transitions were equal to 32 ns.  相似文献   

15.
The electron paramagnetic resonance (EPR) parameters (g factors gxx, gyy, gzz and hyperfine structure constants Axx, Ayy, Azz) are interpreted by taking account of the admixture of d-orbitals in the ground state wave function of the Cu2+ ion in a Zn(C3H3O4)2(H2O)2 (DABMZ) single crystal. Based on the calculation, local structural parameters of the impurity Cu2+ center were obtained (i.e. Ra≈1.92 Å, Rb≈1.96 Å, Rc≈1.99 Å). The theoretical EPR parameters based on the above Cu2+?O2? bond lengths in the DABMZ crystal show good agreement with the observed values and some improvements have been made as compared with those in the previous studies.  相似文献   

16.
陈哲  谢鸿  严有为 《光学学报》2007,27(1):111-115
采用溶液燃烧法在600℃成功合成了(BaxMg)2/(x 1)Al10O17∶Eu2 (0.6≤x≤1.2)蓝色荧光粉,着重研究了基质阳离子Ba/Mg比值的变化对其晶体结构及发光特性的影响。结果表明,合成的产物为纯相,且随Ba/Mg比值的增加,样品的晶格参量逐渐增加;当Ba/Mg比增加时,发射光谱的强度明显增强,至Ba/Mg为0.9时达到最大值,然后随Ba/Mg比继续增大,发射光谱的强度反而下降;Ba/Mg比值减少,导致基质的晶场增强和电子云膨胀效应的发生,致使Eu2 发射主峰向长波方向移动。Eu2 的掺杂浓度对样品的发光性能有显著的影响,随Eu2 浓度增大,发光中心增多,Eu2 离子间相互作用增强,能量传递加快,发光强度逐渐增大,并达到一个最大值。此后,随Eu2 的浓度进一步增加,Eu2 之间的能量传递速率将超过发射速率,呈现浓度猝灭特性。  相似文献   

17.
利用离子辅助电子束沉积方法在LiB3O5基底上镀制了不加SiO2内保护层和加SiO2内保护层的倍频增透膜,测量了两类薄膜在波长1 064 nm多脉冲辐照下的激光损伤阈值,获得了两种不同的损伤形貌,并对损伤原因作了初步探讨。实验结果表明:保护层的加入把由基底膜层界面缺陷吸收所决定的阈值改变到由HfO2膜层内缺陷吸收所决定的阈值,显著提高了倍频增透膜的抗激光损伤能力。  相似文献   

18.
The adsorption of l-cysteine and l-methionine amino acids on a chiral Cu{5 3 1} surface was investigated with high resolution X-ray photoelectron spectroscopy (XPS) and carbon K-edge near edge X-ray absorption fine structure (NEXAFS) Spectroscopy using synchrotron radiation. XPS shows that at 300 K l-cysteine adsorbs through two oxygen, a nitrogen and a sulfur atom, in a four point ‘quadrangular footprint’, whereas l-methionine adsorbs through only two oxygen and a nitrogen atom in a ‘triangular footprint’. NEXAFS was used to clarify the adsorption geometry of both molecules, which suggests a binding orientation to the top layer and second layer atoms in two different orientations associated with adsorption sites on {1 1 0} and {3 1 1} microfacets of the Cu{5 3 1} surface.  相似文献   

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