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钛酸盐因其优异的物理化学性能,可作为高放射性核废物(HLW)和锕系元素(钚)的重要候选固化材料之一。采用传统的陶瓷烧结工艺制备了多晶的Lu2Ti2O7和Lu2TiO5陶瓷材料。在室温下,用800 keVKr2+对两种材料进行辐照,辐照后的样品采用GIXRD进行表征,观察到两种样品都经历了先肿胀、然后再发生非晶相变的过程。不同的是Lu2Ti2O7的晶格肿胀程度大于Lu2TiO5。另外,Lu2TiO5样品的辐照到2×1014 ions/cm2时非晶含量达95.54%,而Lu2Ti2O7样品在此剂量下非晶含量只有74.66%。通过第一性原理计算了Lu2Ti2O7晶体的晶格肿胀随反位浓度的变化关系,结果表明,Lu2Ti2O7出现非晶前的晶格肿胀主要由阳离子反位导致,而Lu2TiO5是无序的萤石结构,其辐照所导致的晶格肿胀不含阳离子反位的贡献,晶格肿胀程度较低。 相似文献
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在Si-Al2O3复合薄膜中观察到室温铁磁性.Si的体积百分比为15 %的Si-Al2O3复合薄膜的磁性最强.Si的含量影响样品的磁有序,在样品中观察到了明显的磁畴.在不同气氛下,对样品进行快速热退火.退火样品的磁性测试结果的差别表明氧空位不是样品铁磁性的主要来源.我们认为铁磁性来源于Si与Al2O3基质界面之间的缺陷的磁耦合.改变Si的含量可以改变缺陷密度,从而控制铁磁耦合强度.
关键词:
2O3薄膜')" href="#">Al2O3薄膜
室温铁磁性
掺杂
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J. Bieger H. Adrian P. Müller G. Saemann-Ischenko E.L. Haase 《Solid State Communications》1980,36(11):979-982
Low temperature irradiation of thin films of Nb75Ge25 (Tc = 3.2 K) and Nb80Si20 (Tc = 4.7 K) with 20 MeV sulfur ions leads to an increase of Tc of about 0.5 K and a decrease of ? of about 1.5 to 3.5%. Annealing up to room temperature partly restores the initial values. Qualitatively the results can be explained by irradiation induced smearing of the structure factor, which is partially recovered by annealing. 相似文献
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Single crystals of δ-NbN0.85 with a superconducting transition temperature Tc of 14.3 K were implanted with nitrogen and carbon ions at room temperature and subsequently annealed at high temperatures. Implantation was also performed at high substrate temperatures. After implantation at about 920°C maximum Tc-values of 16.5 and 17.8 K were obtained with N- and C-ions respectively. Disorder observed after room temperature implantation consisted of displaced Nb-atoms which could not be completely annealed in an isochromous annealing process up to 1000°C. For annealing temperatures above 1100°C nitrogen diffusion out of the implanted layers resulted in a reduction of Tc. 相似文献
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A. Varilci D. Yegen M. Tassi D. Stamopoulos C. Terzioglu 《Physica B: Condensed Matter》2009,404(21):4054-4059
A commercially available powder of MgB2 is used as starting material for the examination of the influence of the annealing temperature on the properties of this intermediate-Tc superconductor. We performed scanning electron microscopy (SEM) and Hall ac-susceptibility measurements as a function of temperature and ac-field amplitude on samples annealed at 650, 750, 850 and 950 °C. The imaginary part of ac-susceptibility measurements is used to calculate both the inter-granular critical current density, Jc(Tp) and density of pinning force, αj(0). It was observed that all Tc, Jc(Tp) and αj(0) exhibit a non-monotonic behavior on the annealing temperature range studied in this work. Tc is measured to be 39.85±0.02 K and Jc(Tp) is estimated to be as high as 60 A/cm2 at 39.2 K for the sample annealed at 850 °C. The peak temperature, Tp, in the imaginary part of the ac-susceptibility curves shifts to lower temperatures with both decreasing the annealing temperature and increasing the amplitude of the ac-magnetic fields. A comparison of the experimental ac-susceptibility data with theoretical critical-state models that are currently available is performed. SEM investigations showed that the grain size increases, and the grain connectivity improves when the annealing temperature increases up to 850 °C. The possible reasons for the observed changes in transport, microstructure and magnetic properties due to annealing temperature are discussed. 相似文献
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April O’Brien Brendon Villegas J.Y. Gu 《Physica C: Superconductivity and its Applications》2009,469(1):39-43
Magnesium diboride (MgB2) thin films were deposited on C-plane sapphire substrates by sputtering pure B and Mg targets at different substrate temperatures, and were followed by in situ annealing. A systematic study about the effects of the various growth and annealing parameters on the physical properties of MgB2 thin films showed that the substrate temperature is the most critical factor that determines the superconducting transition temperature (Tc), while annealing plays a minor role. There was no superconducting transition in the thin films grown at room temperature without post-annealing. The highest Tc of the samples grown at room temperature after the optimized annealing was 22 K. As the temperature of the substrate (Ts) increased, Tc rose. However, the maximum Ts was limited due to the low magnesium sticking coefficient and thus the Tc value was limited as well. The highest Tc, 29 K, was obtained for the sample deposited at 180 °C, annealed at 620 °C, and was subsequently annealed a second time at 800 °C. Three-dimensional (3D) AFM images clearly demonstrated that the thin films with no transition, or very low Tc, did not have the well-developed MgB2 grains while the films with higher Tc displayed the well-developed grains and smooth surface. Although the Tc of sputtered MgB2 films in the current work is lower than that for the bulk and ex situ annealed thin films, this work presents an important step towards the fabrication of MgB2 heterostructures using rather simple physical vapor deposition method such as sputtering. 相似文献
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X-band electron paramagnetic resonance (EPR) spectra of a GdBa2Cu3O7−y single crystal were obtained at room temperature before and after reducing its oxygen content by, annealing. Before annealing, the sample exhibited superconductivity atT c≊90 K; the EPR line was asymmetrical and was described with a Dysonian shape because of the skin effect. After annealing, superconductivity was not observed; the EPR line, less affected by the skin effect, was symmetrical and more intense, approximately described with a Lorentzian shape. 相似文献
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Abstract We have studied the effects of fast neutron (E>0.1 MeV) irradiation at reactor (~ 360 K) and low (~ 20 K) temperatures on the superconducting properties of polycrystalline orthorhombic YBa2Cu3O7?y . Measurements were made on the superconducting critical temperature Tc , critical current Jc , Meissner effect and magnetic field dependence of Jc . The Tc drops by an irradiation at reactor temperature and Jc increases with increasing fluence. On the other hand with the irradiation at low temperature, Tc rises and Jc increases. Results of observation of Meissner effect and the magnetic field dependence of Jc are consistent with the behavior of Tc and Jc . 相似文献
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S. Klaumünzer G. Ischenko P. Müller 《Zeitschrift für Physik A Hadrons and Nuclei》1974,268(2):189-196
To study the effects of heavy ion irradiation at low temperature on type II superconductor Nb, the transition temperatureT c , the normal state residual resistivityρ B , the transition widthΔT ph using oxygen ions of 25 MeV and subsequent thermal annealing were measured. The samples were held at temperatures <20 K during irradiation in a cryostat for in situ measurements. The maximum oxygen fluence was about 2·1015 cm?2 corresponding a relatively high defect concentration. The heavy ion irradiation experiments are described. The critical temperatureT c decreases with increasing residual resistivityρ B . In agreement with the theory and experiments, the gap anisotropy parameter is 〈a 2〉=0.008, subsequent annealing shows a hysteresis ofT c versusρ B . The resistivity saturation value ΔρBS = 2.55 μΩ cm was obtained and different recovery stages were found. Significant broadening of transition width during irradiation was observed.T c andΔT ph anneal to 60% in the temperature interval of (60–90) K. Oxygen induced effects as a simulation method of high neutron damage are compared with irradiation measurements using neutrons and deuterons. 相似文献
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This paper reports that Zn0.97Mn0.03O thin films
have been prepared by radio-frequency sputtering technology followed
by rapid thermal processing in nitrogen and oxygen ambient
respectively. Magnetic property investigation indicates that the
films are ferromagnetic and that the Curie temperature (Tc) is over
room temperature. It is observed that the saturation magnetization
of the films increases after annealing in nitrogen ambience but
decreases after annealing in oxygen. Room temperature
photoluminescence spectra indicate that the amount of defects in the
films differs after annealing in the different ambiences. This
suggests that the ferromagnetism in Zn0.97Mn0.03O films is
strongly related to the defects in the films. 相似文献