共查询到20条相似文献,搜索用时 656 毫秒
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在较宽的温度(4.2-80K)和磁场(0-8T)范围内测量了YBa2Cu3O7-δ和Y0.9Eu0.1Ba2·Cu3O7-δ样品的磁滞回线和磁弛豫,研究了其M(t),Jc(T)和Ueff(J)关系,并与现有的一些理论模型所预言的结果进行了比较。结果表明:(1)与YBa2Cu3O7-δ相比,Y0.9Eu0.1·Ba2Cu3O7-δ样品的有效钉扎势和无磁通蠕动时的临界电流密度有明显提高,表明Eu的部分替代引入了新的、具有更大的钉扎势的钉扎中心;(2)与其它模型相比,集体钉扎——蠕动理论对我们的实验结果作了更好的描述,因而本文为这一理论提供了新的实验证据。
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研究了Gd1-xCaxBa2Cu3O7-y(0.0≤X≤0.20)高温超导体在常压和高压下的超导电性在1-300K温度范围内,利用Bridgman对顶砧获得压力达9.0GPa,测量了(X=0.10,0.15,0.20)样品的dTc/dp分别为7.68,7.8和4.46K/GPa。发现Tc的压力导数随着ca2+含量的增加而下降,分析了氧含量对Tc和dTc/dP的影响.利用常压下晶格参数精修值和阳离子与氧离子间距随压力的改变,说明CuO2面在超导电性上的作用,用CuO2面之间耦合解释Tc(P)曲线的非线性关系。
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报道在超声射流冷却条件下用同步辐射VUV光源研究CH2Br2的振动自电离结构.根据测量的105—123nm范围内母体离子(CH2Br2+)的光电离产率曲线,获得CH2Br2的绝热电离势为10.23±0.01eV.CH2Br2+的最低三个电子激发态,即A(2A2),B(2B1),C(2A1)分别位于10.78±0.01eV,11.20±0.01eV和11.27±0.01eV.在115.01—121.15nm范围内,观察到CH2Br2自电离峰叠加在若干台阶结构上,台阶平均宽度为716.8±40.0cm-1,对应于CH2Br2+(X2B2)中Br-C-Br反对称的伸缩振动(v9),所有的峰均归属为收敛于CH2Br2+(X2B2,v+)振动能级的ns,np和nd自电离Rydberg态.此外,对CH2Br2光解离电离产生离子型自由基CH2Br+(X)的光电离产率曲线的结构也进行了归属
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用深能级瞬态谱(DLTS)和恒温电容瞬态等技术研究了浅杂质注入LEC半绝缘GaAs的γ射线辐照缺陷。在Be-Si共注的LEC半绝缘GaAs中,γ射线辐照引入一电子陷阶E2,并且大大增强了原有的E01(0.298)和E02(0.341)等缺陷,同时明显地瓦解了原有的少子陷阱H03。在单纯注Si的LEC半绝缘GaAs中,γ射线辐阳引进了E'01(0.216),E'02(0.341),E'2,E'4和E'5(0.608)等缺陷。其中E01和E'01是新发现的和γ辐照有关的GaAs缺陷。和低阻衬底同质外延GaAs相比,Be-Si共注LEC半绝缘GaAs具有较低的γ射线辐照缺陷引入率,与此相反,单纯注Si的LEC半绝缘GaAs具有较高的γ射线辐照缺陷的引入率。
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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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Dheeraj Jain 《Journal of luminescence》2009,129(5):439-3684
Zinc phosphate glasses doped with Gd2O3:Eu nanoparticles and Eu2O3 were prepared by conventional melt-quench method and characterized for their luminescence properties. Binary ZnO-P2O5 glass is characterized by an intrinsic defect centre emission around 324 nm. Strong energy transfer from these defect centres to Eu3+ ions has been observed when Eu2O3 is incorporated in ZnO-P2O5 glasses. Lack of energy transfer from these defect centres to Eu3+ in Gd2O3:Eu nanoparticles doped ZnO-P2O5 glass has been attributed to effective shielding of Eu3+ ions from the luminescence centre by Gd-O-P type of linkages, leading to an increased distance between the luminescent centre and Eu3+ ions. Both doped and undoped glasses have the same glass transition temperature, suggesting that the phosphate network is not significantly affected by the Gd2O3:Eu nanoparticles or Eu2O3 incorporation. 相似文献
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Electrical conductivity and thermopower measurements are reported for the defect semiconductors p-In2Te3 and n-Ga2Te3. The hole mobility μp in the former varied as Tnwheren=+5.98 forT<350 K and n=-4.13 forT>350 K showing a maximum of 210 cm2V-1 sec-1 at 350 K. Electron mobility in n-Ga2Te3 also went through a maximum at 320 K. The optical band-gaps for both were found to be direct, with values of 1.01 and 1.08 eV for In2Te3 and Ga2Te3 respectively at 300 K. Pronounced effects of annealing on TEP and optical absorption gave evidence of defect ordering at low temperatures followed by defect creation at T>350 K. 相似文献
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采用从头计算B3LYP,MP3和MP4方法结合Aug-cc-pVDZ基组研究了CH3C(O)OSSOC(O)CH3最稳定的五种构象及其阳离子构型.理论计算了五种稳定构象的转动常数和偶极矩;运用电子传播子理论P3近似方法计算稳定构象外价壳层轨道的电离能,计算结果与光电子能谱实验结果符合的较好.根据构象的相对能量以及理论模拟电离能谱和实验光电子能谱之间的比较,说明在气相光电子能谱实验中至少存在两种构象.与中性构型相比,电离后的五种阳离子构型均发生了明显的结构弛豫,尤
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构象
电离能
相对能量
光电子能谱 相似文献
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The electrical properties of α-(Al0.02In0.98)2Se3 were investigated. In contrast to In2Se3, which is characterized by a high and constant concentration of donorlike defect centers, the concentration of active donors in α-(Al0.02In0.98)2Se3 can be changed in a reversible manner over four orders of magnitude by thermal treatment. To explain this strange behavior, we have proposed a simple model, which presumes formation of complex defect centers consisting of Al atoms at cation sites and native donors. 相似文献
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Rana N.S. Sodhi C.E. Brion 《Journal of Electron Spectroscopy and Related Phenomena》1985,37(1):125-144
Electron energy loss Spectroscopy has been used to obtain the inner shell excitation spectra of PF5, OPF3 and OPCl3 in the P 2p,2s (L-shell) region as well as in the respective ligand K shell (F 1s, O 1s) and L shell (Cl 2p and 2s) regions. The spectra are compared and contrasted with earlier reported spectra obtained on the trivalent phosphorus compounds (PH3, PCl3, PF3 and P(CH3)3). The spectra were obtained using an impact energy of 2.5keV and a scattering angle of about 1°. The spectra reported here are typical of molecules with electronegative ligands in that the discrete portions of the spectra show strong transitions to virtual molecular orbitais. In addition, intense features are observed at or just beyond the ionization edge attributable to transitions to trapped inner well states, while broad features further into the continuum can be ascribed to σ*(P—L) shape-resonances (L = ligand). This resonance assignment was supported by a comparison with the corresponding spectra for PF3 and PCl3. 相似文献
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V. Sudarsan 《Journal of luminescence》2010,130(8):1379-1383
Binary (ZnO)0.5(P2O5)0.5 glasses doped with Eu2O3 and nanoparticles of Gd2O3:Eu were prepared by conventional melt-quench method and their luminescence properties were compared. Undoped (ZnO)0.5(P2O5)0.5 glass is characterized by a luminescent defect centre (similar to L-centre present in Na2O-SiO2 glasses) with emission around 324 nm and having an excited state lifetime of 18 ns. Such defect centres can transfer the energy to Eu3+ ions leading to improved Eu3+ luminescence from such glasses. Based on the decay curves corresponding to the 5D0 level of Eu3+ ions in both Gd2O3:Eu nanoparticles incorporated as well as Eu2O3 incorporated glasses, a significant clustering of Eu3+ ions taking place with the latter sample is confirmed. From the lifetime studies of the excited state of L-centre emission from (ZnO)0.5(P2O5)0.5 glass doped with Gd2O3:Eu nanoparticles, it is established that there exists weak energy transfer from L-centres to Eu3+ ions. Poor energy transfer from the defect centres to Eu3+ ions in Gd2O3:Eu nanoparticles doped (ZnO)0.5(P2O5)0.5 glass has been attributed to effective shielding of Eu3+ ions from the luminescence centre by Gd-O-P type of linkages, leading to an increased distance between luminescent centre and Eu3+ ions. 相似文献