压力对不同Tc的Bi2+xSr2Ca1-xCu2Oy单晶超导电性的影响

 在研究BiSrCaCuO超导单晶的过程中，我们发现材料的实际化学组分与理想的2212相配比组分有着一定的差别，正是这种成分偏析造成了样品的T_c与结构的不同。本文研究了在压力下不同T_c的样品随压力改变T_c的变化关系，发现偏析越大、T_c越低的样品的dT_c/dp也越大，而越接近理想组分，则dT_c/dp越趋于最小值，还可以从此推断出BiSrCaCuO理想单晶材料的T_c最佳值。压力对超导电性的这种影响可能与耦合链长的变化有关。     

非晶La80Al20晶化相的超导电性

 本文把非晶La₈₀Al₂₀在真空中、不同温度及其时间条件下进行退火，以及在6 GPa不同温度退火40 min，并对退火样品的相结构及超导性进行了研究。发现真空中，250 ℃退火的样品晶化成了T>4.2 K、不超导的单相四方La₄Al；300 ℃及450 ℃退火的样品晶化成La₃Al、α-La、β-La及一些未知杂相，这些多相混合物的T_C<6.0 K。在6 GPa 300 ℃及以下温度退火的样品，晶化成单相六角La₄Al，其晶格常数与六角La₃Al的完全相同，这些样品的T_C>5.1 K；6 GPa、350 ℃及以上温度退火的样品，晶化成La₃Al相及新未知相H，新相H的T_C约为6.3 K。     

压力对TlPbxBaCa3Cu3O超导电性的影响

 在零电阻温度T_c0达到120 K的TlBaCa₃Cu₃O_y超导体中，掺入不同含量的Pb后，超导电性受到抑制，点阵常数减小。加压时，T_c先随压力p的增加而上升，样品1（x_Pb=0.05）的dT_c0/dp=1.7 K/GPa，样品2（x_Pb=0.5）的dT_c0/dp=2.2 K/GPa。T_c的峰值随Pb的增加而减小。加压时，对由于Pb的加入引起的Cu—O层的精细结构变化起到调制作用。     

压力对HgBa2Ca2Cu3O8+y超导转变温度的影响

 利用低温超高压装置，测量了Hg系样品HgBa₂Ca₂Cu₃O_8+y（Hg-1223）超导转变温度T_c在压力作用下的增强效应。压力最高达7.8 GPa，超导起始转变温度常压下为130 K，加压到5.4 GPa时获得最高温度为140 K。在5.4 GPa以下获得dT_c/dp为1.85 K/GPa。用压力作用下氧原子位置的改变使载流子浓度提高和CuO₂面间的耦合作用来解释高温超导的压力效应。     

高温超导体低温、高压下的物理性质的研究

 在3~20 GPa压力范围内，测量了含氧量较低的YBa₂Cu₃O_7-δ（δ=0.46）单晶压力增强效应（dT_c/dp=4.9KGPa^-1）；YBa₂Cu₃O₇（T_c0=90 K）单晶在压力下临界电流密度随压力变化；外磁场H=30 kO_e时，T_c与磁场、压力关系；压力达16.5 GPa下，Bi₂Sr₂CaCu₂O_x单晶T_c(p)关系（dT_c/dp=-0.4 KGPa^-1）。发现Y系高温超导体的温度压力导数dT_c/dp与T_c0中间呈dT_c/dp=b-mT_c0线性关系（b、m为常数）。结合压力下Y系超导体结构相变和含氧量对T_c影响，分析这类超导体T_c有很强的正压力效应的原因。把实验结果同几种超导电性微观理论模型进行了分析和比较。     

La2CuO4+δ和La2-xSrxCuO4系统中的电子输运性质

 本文解释了La₂CuO_4+δ（0≤δ≤0.09）和La_2-xSr_xCuO₄（0≤x≤0.3）两种p型系统含铜稀土氧化物中的电阻和Seebeck系数与温度的依赖关系，在室温以上，一氧大气压下的La₂CuO_4+δ系统趋于失氧；在500 K以上，超导样品显示出失氧的一级相变，并且恢复到反铁磁相。在转变温度T₁≈300 K以下，对0<δ<0.05成份的样品，相分离成反铁磁相和超导相；而在T_cρ≈100 K的温度范围内，超导相进一步分离成富空穴和贫空穴畴。在0.04≤δ≤0.09范围内，T_c处的电阻陡降出现了台阶；我们认为，它反映了电子成对的起伏。在La_2-xSr_xCuO₄系统中，对于成分为01≈300 K以上，空穴的运动是弥散的，但是ΔH_m=0；而对于x≥0.22的样品，经历了从平滑到Fermi液态的转变。成份为0c1范围（其中空穴继续以弥散方式运动）是亚稳的，但是，在T_cρ≤150 K范围，出现了电荷起伏。当样品冷却通过T₁时，对于成份为0.15≤x≤0.2的样品，经历了由弥散到强质量增强巡游电子状态的转变；在T_c处，从均匀的修饰电子的正常态凝聚成超导的载流子对。在超导成份样品的正常态中，不寻常的电子-晶格相互作用，可以归结为在CuO₂面上从更离子性的到共价性的Cu:3d_x²-r²─O:P_σ键合的转变；通过这种转变，轨道杂化和Hubbard U参量随Cu─O键长和Cu原子上的外表局域氧化态都产生灵敏的变化。     

高压处理对BiSrCaCu2Oy超导电性的影响

 本文在高T_c超导体BiSrCaCu₂O_y常压制备的基础上，研究了热压烧结和冷压处理对其形成、结构及超导电性的影响，并与常压结果进行了比较。结果表明，高压可以使样品的合成时间缩短，合成温度降低。但同时它也抑制了晶格参数较大的相（高T_c相）的形成，使小晶格参数的杂相含量增多。对于提高样品的超导电性而言，1.5 GPa时一个较好的压力点。     

加压对110 K Bi-Pb-Sr-Ca-Cu-O单相样品超导电性的影响

 在静压0~1 GPa（10 kbar）范围内，80~300 K温区，用测量电阻的方法，研究了Bi-Pb-Sr-Ca-Cu-O（起始转变温度T_c^on=110 K，终止转变温度T_c^fi=106 K）的起导电性。观察到超导临界温度T_c随压力以dT_c/dp=2K/GPa的速率增高，而在不同压力下的斜率d logR/dp却保持不变。     

静高压下非晶(Fe0.99,Mo0.01)78Si9B13合金晶化过程的热力学研究

 在600~930 K，常压到7 GPa的范围内，对非晶(Fe_0.99,Mo_0.01)₇₈Si₉B₁₃合金等温等压退火30 min。实验表明：其晶化产物α-Fe(Mo, Si)、Fe₃B和Fe₂B相的析出与所加压力密切相关。压力使非晶(Fe_0.99,Mo_0.01)₇₈Si₉B₁₃合金的晶化温度和亚稳Fe₃B相的析出温度下降，在一定的压力和温度下，亚稳Fe₃B相将向稳定Fe₂B相转变，其转变温度随压力而变化。还对非晶(Fe_0.99,Mo_0.01)₇₈Si₉B₁₃合金的晶化和亚稳Fe₃B到稳定Fe₂B转变的热力学机制进行了讨论，并给出Fe₃B向Fe₂B的相转变方程。     

高压对高温超导体La1.85Sr0.15CuO4电子结构的影响

 采用Recursion方法计算了常压和1 GPa、4 GPa、8 GPa高压下La_1.85Sr_0.15CuO₄的电子结构，给出了费米能、费米能处态密度以及各晶位原子价的定量变化。结果表明：高压下T_c的变化可能源于CuO₂面上氧空穴和铜空穴数目的改变，且氧空穴数目的增加有利于超导性。     

Creep strain recovery of Fe-Ni-B amorphous metallic ribbon

Creep strain recovery and structural relaxation of the amorphous metallic glass Fe₄₀Ni₄₁B₁₉ after longtime loading at different annealing temperatures below the glass transition temperature have been studied using anisothermal differential scanning calorimetry (DSC) and dilatometry (TMA). It has been demonstrated that structural relaxation effects depend on the stress-annealing temperature of the amorphous ribbon. The structural relaxation states of the amorphous ribbon annealed at different temperatures under and without applied stress have been compared. The activation energy spectra were calculated from the anisothermal dilatometric measurements using the modern method based on the Fourier transformation technique. The influence of the annealing temperature on the shape of creep strain recovery spectra has been analyzed.      

Annealing behaviour of nanocrystalline NiTi (50 at% Ni) alloy produced by high-pressure torsion

An equiatomic nanocrystalline NiTi alloy, deformed by high-pressure torsion (HPT), was investigated. The as-prepared bulk NiTi alloy consisted of both amorphous and nanocrystalline phases. Crystallization and structural changes during annealing were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). DSC thermograms and X-ray analyses revealed stress relaxation and partial crystallization below 500?K, while grain growth of the nanocrystals occurred predominantly after heating to temperatures above 573?K. Along with the amorphous phase crystallization, a continuous growth of pre-existing nanocrystals that are retained after HPT was observed. The DSC signals observed during continuous heating experiments indicate an unusually large separation between the crystallization and growth stages. A detailed analysis of the evolution of the enthalpy release upon annealing revealed reproducibly non-monotonous trends with annealing temperature that cannot be explained solely by nucleation and growth of crystalline volume fractions. Instead, the results can be rationalized by assuming a reverse amorphization process occuring during annealing at 523?K. This behavior, which also caused a large variation in nanocrystal size after annealing at higher temperatures, is discussed with respect to the nanoscale microstructural heterogeneity after initial deformation processing.     

Blistering kinetics in H-implanted 4H-SiC for large-area exfoliation

Layer transfer of single-crystalline SiC based on layer splitting and wafer bonding on an alternate substrate is a viable approach to fabricate SiC power devices at a lower cost. Dependence of implantation-induced surface blistering and exfoliation of thin layers, on the implantation parameters and subsequent annealing conditions, for large area exfoliation of 4H-SiC have been studied. We report the optimization of the annealing process (one-step or two-step) and annealing parameters like temperature and time to achieve large area exfoliation of SiC. Using the Föppl-von Karman (FvK) theory, the pressure inside the blister cavities and implantation-induced stress inside the damage region have been studied. We deduce that pressure inside the blister depends primarily on the blister size. HRXRD analysis has been used to determine the strain relaxation behavior as a function of annealing conditions. Raman spectroscopy and STEM measurements revealed the formation of defects inside the material due to ion implantation. AFM, Nomarski, and SEM were used to measure the size and depth details of the blisters as a function of annealing temperature and time. We have successfully exfoliated large area (up to 500 μm) in a two-step annealing process. The results reported in this paper are useful for SiC layer transfer on an arbitrary substrate by the Smart Cut process.     

用原位x射线小角散射研究块体非晶合金Zr55Cu30Al10 Ni5的结构弛豫

应用同步辐射x射线小角散射法在原位对块体非晶合金Zr₅₅Cu₃₀Al ₁₀Ni₅在等温退火过程中的微结构变化进行研究.实验表明：在等温退火过程中电子 密度涨落反映了晶化之前的结构弛豫过程；在一定的退火温度下、随退火时间的增加，拓扑短程序弛豫与化学短程序弛豫之间存在一个电子密度均匀化的过程；导致这两种弛豫过程转变的退火时间与退火温度有关，温度越高，所需的退火时间越短. 关键词： 原位x射线小角散射 块体非晶合金 等温退火 结构弛豫     

非晶态超导合金Zr87.7Si12.3中结构弛豫和结晶化对超导

对非易态超导合金Zr_87.7Si_12.3,在适当的温度下进行了lh等时退火处理.测量了其结构、超导临界参量T_c,H_(C2)及其转变宽度ΔT_c,ΔH_c2等的变化.发现些与金属-金属型非晶态合金不同的变化规律,并结合在结构弛豫过程中所发生的拓扑短程有序化和化学短程有序化,以及相应的结晶化机制,对实验结果作了讨论. 关键词：     

Structural relaxation and chemical decomposition in amorphous TM-M alloys

Small angle X-ray scattering experiments performed on amorphous two-component transition metal-metalloid alloys have shown that these materials decompose on annealing clearly before crystallization starts. This process influences the behaviour of physical properties in a similar way as structural relaxation does. To separate the two effects mainly composition dependent properties must be compared with others which are mainly sensitive to structural changes. In this paper it is shown that the ratio of the annealing-induced changes of the temperature coefficient of the resistivity and of the residual resistivity is determined by the underlying elementary process. The two values resulting for predominating structural relaxation and for predominating decomposition seem to be universal and are compatible with a theory of phonon-controlled conductivity in high-resistance conductors.     

低温高压及高温高压对La80Al20非晶态结构及超导性的影响

用X射线衍射照相、X射线衍射仪及透射电子显微镜分析了用液相淬火技术制备的La₈₀Al₂₀合金样品,结果表明样品是非晶态结构。差热分析(DTA)结果表明,非晶态样品的晶化温度T_cr为280℃左右,玻璃温度T_g为242℃左右。非晶态样品低温高压(流体静压法)试验结果表明:压力从0至4.77kbar,T_c从3.87K提高到4.18K。高压下,超导前的剩余电阻与常压下相比较有明显下降。非晶态样品经高温高压 关键词：     

Effect of structural relaxation on the low temperature thermal properties of the superconducting amorphous alloy Zr .76Ni 0.24

We have measured the low temperature (from 50 mK up to 5 K) specific heat and thermal conductivity of an amorphous ZrNi superconducting alloy as sputtered and after annealing in the amorphous state. We observe after annealing a decrease of the specific heat anomaly below 0.5 K together with an increase of the thermal conductivity. These variations are in agreement with a decrease of the density of two-level systems (T.L.S.) due to the structural relaxation.     

非晶态Cu_(56)Zr_(44)合金的结构及其等温退火晶化过程的研究

利用X射线衍射技术、差示扫描量热分析技术和透射电子显微镜研究了非晶态Cu56 Zr4 4合金的结构及其等温退火条件下的晶化过程 .实验结果表明 ,非晶态Cu56 Zr4 4合金在室温下的短程结构类似于硬球无规密堆积分布 .在70 3K过冷液相区内等温退火时发现 ,当退火时间为 3min时 ,晶化产物主要为Cu8Zr3相 ;当退火时间为 6min时 ,Cu8Zr3相完全消失 ,而Cu1 0 Zr7相大量析出 ;当退火时间达到 3 0min以上时 ,其晶化产物转变为Cu1 0 Zr7,CuZr2 ,Cu8Zr3等多种化合物 .由此提出了非晶态Cu56 Zr4 4合金等温退火晶化过程的扩散机理 .     

非晶态InSb及其亚稳中间相的霍耳效应和超导电性

实验研究了非晶态InSb及其结晶相变过程中的霍耳效应. 结果表明, 金属型非晶态InSb以电子导电为主, 半导体型非晶态InSb 以空穴导电为主; 金属型非晶态InSb中的第一电导跃变是一种由类液非晶态到类点阵非晶态的结构弛豫过程; 第三电导跃变是富In或富Sb 固溶体相在半导体InSb 晶界上析出并集中所引起的; 金属型非晶态I站b 的三种不同的结晶相变类型具有鲜明不同的输运性质; 第二电导跃变峰所对应的亚稳金属相超导Tc的提高, 可能主要起因于电子浓度的增加. 关键词：