非晶态(Fe1-xCrx)84B16合金的低温热电势

在80—380K之间对(Fe_1-xCr_x)₈₄B₁₆(x=0.01—0.46)非晶态合金的绝对热电势S进行了测量,结果表明,磁性非晶合金的S(T)行为并不都是非线性并有一个浅的极小。少量Cr(x≤0.05)的加入使S的绝对值减小,并使S(T)的极小消失;当Cr含量较多时,样品磁性变弱,S(T)从典型的磁性非晶合金的非线性行为过渡到接近于非磁性非晶合金的线性行为。对x=0.15,0.25的样品,其居里点正落在我们测量的温 关键词：     

非晶态(Fe_(1-x)Cr_x)_(84)B_(16)合金的低温热电势

在80—380K之间对(Fe_(1-x)Cr_x)_(84)B_(16)(x=0.01—0.46)非晶态合金的绝对热电势S进行了测量,结果表明,磁性非晶合金的S(T)行为并不都是非线性并有一个浅的极小。少量Cr(x≤0.05)的加入使S的绝对值减小,并使S(T)的极小消失;当Cr含量较多时,样品磁性变弱,S(T)从典型的磁性非晶合金的非线性行为过渡到接近于非磁性非晶合金的线性行为。对x=0.15,0.25的样品,其居里点正落在我们测量的温度范围内,经过仔细的测量,在居里点T_c附近没有看到S的反常。     

Cr对Fe-Zr基非晶合金电阻率及压力效应的影响

 在0.000 1~2.5 GPa范围不同静水压下，用四探针法详细测量了七种非晶态Fe_90-xCr_xZr₁₀合金（x=2、4、7、10、13、16、20）的电阻率。结果表明：（1）常压室温电阻率ρ₀与FeZr基非晶合金中Cr含量成N形曲线关系；（2）当静水压增加时，七种非晶合金的约化电阻率（ρ/ρ₀）都单调下降，x越大则电阻率下降的幅度越小；（3）非晶Fe_90-xCr_xZr₁₀合金电阻率的压力系数对x的变化相当敏感；（4）为方便查值，给出了六种典型静水压下ρ/ρ₀与x的曲线关系。最后，讨论了四种物理模型的选用以及相干交换散射在高压下的行为。     

非晶Nb-Ni合金晶化过程中紫外光电子能谱研究

本文利用紫外光电子能谱和X射线衍射测量研究了非晶Nb_100-xNi_x(x=65,59.8,56.4)合金晶化过程中价带谱的变化。对NbNi₃价带谱中出现的双峰进行了讨论。 关键词：     

Zr-Cu-Ni-Al-Nb大块非晶合金的晶化行为、力学性能及电化学腐蚀行为的研究

利用水冷铜模铸造法成功制备了Zr_65-xCu_17.5Al_7.5Ni ₁₀Nb_x (x=0，2，5)大块非晶合金. X射线衍射、热分析研究结果表 明，Nb的添加显著改变了非晶合金的晶化行为，促进了二十面体准晶相的形成. 各合金的准 静态压缩实验表明，Nb的适量添加有利于提高大块非晶合金的强度和塑性. 其中x=5的大块 非晶合金的抗压强度σ_b和塑性应变量ε_p 关键词： Zr基大块非晶合金 晶化行为 力学性能 耐腐蚀性能     

非晶态(Fe_(1-x)V_x)_(84)B_(16)合金的磁性和电性

用单辊急冷法制备了非晶态(Fe_(1-x)V_x)_(84)B_(16)(x=0,0.02,0.04,0.06,0.10)合金的薄带,分别用磁天平和四端引线法测量了饱和磁化强度和高温电阻率的温度关系。得到平均每个磁性原子的磁矩随V含量的增加近似线性下降,计算出每个Fe原子和每个V原子的平均磁矩分别为2.08μ_B和-5.08μ_B。居里温度T_c从x=0时的622K下降到x=0.10时的478K。利用自旋波激发公式:σ(T)=σ(0)(1-BT~(3/2)-CT~(5/2))得到,自旋波劲度系数D在75.4-81.8(meV·)之间(x=0-0.10),交换相互作用范围的平方平均值〈r~2〉从x=0.02时的4.4增加到x=0.10时的6.5。电阻率的测量得到,室温电阻率在155-127(μQ·cm)之间,晶化过程中电阻率的下降幅度随V含量增加而线性减小,其原因与晶化过程中的相变有关。     

穆斯堡尔谱学研究非晶TM80M20合金的微观结构

在室温下和4.2K下测定了非晶Fe₈₀B_20-xM_x合金(M=P,C)的穆斯堡尔吸收谱。利用分布参数拟合程序得到了超精细内场H_i和同质异能移IS同类金属成份的变化关系。利用这些结果考察了非晶合金的微观结构,比较了两类结构模型:Bernal-Polk模型和微晶模型。对比非晶合金和它们的相应晶相的行为得知,这类非晶合金中不存在微晶近程序,Bernal-Polk模型对描述TM-M类非晶合金的微观结构优于微晶模型。 关键词：     

基于剪切模量和热分析数据研究Zr_(50–x)Cu_(34)Ag_8Al_8Pd_x(x=0,2)非晶合金缺陷浓度演化

非晶合金具有独特物理和力学性能,如何建立非晶合金微观结构非均匀性与物理/力学性能之间的关联是非晶固体的重要研究课题之一.微合金化是调控非晶合金微观结构有效手段之一.本研究以玻璃形成能力优异的Zr_(50–x)Cu_(34)Ag_8Al_8Pd_x(x=0, 2)非晶合金为模型合金,借助差示扫描量热仪和电磁声转换设备,研究非晶合金铸态、弛豫态和结晶态热流和剪切模量随温度的演化规律,以及物理时效(低于玻璃转变温度)过程剪切模量的变化随时间演化规律.基于自间隙原子理论,利用热流曲线表征非晶合金在相同热历史剪切模量热效应.通过分析铸态和弛豫态自间隙缺陷浓度和激活能谱,发现结构弛豫导致自间隙缺陷浓度减小,诱导剪切模量随温度演化偏离软化过程,并伴随体系放热.与此同时,研究发现添加微量Pd元素可抑制模型合金体系原子迁移,增加特征弛豫时间.本研究从非晶合金模量热效应角度进一步理解非晶合金微观结构非均匀性.     

非晶态Fe_(90-x)Cu_xZr_(10)合金的电子输运特性和结构弛豫

对非晶态Fe_9(1-x)Cu_xZr_10(x=0,4,6,8,10,15,20)合金的低温电阻率、热电势率、高温电阻率和循环退火过程中的电阻率进行测量,结果表明:样品低温电阻率在T_c.附近出现极小值,可用相干交换散射模型说明,热电势率在77—380K间为负值,可用Motts-d散射模型解释:高温电阻率与温度关系和Ziman理论不一致,是相分离的结果;可逆和不可逆结构弛豫分别与CSRO和TSRO有关 关键词：     

非晶态Fe_(90-x)Cr_xZr_(10)合金的相干交换散射效应

用四探针法在1.5—300K温度范围测量了非晶态Fe_(90-x)Cr_xZr_(10)(x=0,2,7,10,13,16和20)合金的电阻率与温度的关系。观察到所有样品在其居里温度附近都呈现出电阻率极小值。对这一实验结果用相干交换散射模型作了定性解释。     

用赝势微扰法计算某些半导体的能带结构(用于GaAs,GaP和Ga[As1-xPx]合金)

用赝势微扰法计算了GaAs,GaP和Ga[As_1-xP_x]合金的能带。赝势选择的原则是使计算所得直接能隙和间接能隙与实验值相符合。计算结果表明,不但能带次序准确,而且与室温下的实验值符合得很好。基于由GaAs到GaP晶格常数和赝势是线性变化的假设,计算了GaP含量为20％,50％和80％时Ga[As_1-xP_x]合金的能带。当GaP含量为41％时,直接能隙和间接能隙相等,这一数值刚好是Spitzer和Fenner的实验值的平均值。此时,由于很好满足光激射器p-n结所要求的条件,因此可望在光激射器中得到应用,它们的能带也就有一定的参考价值。     

Structural and Mössbauer studies of Fe1−xAlx alloys over the entire composition range

Metastable Fe_1?xAl_x alloys over the entire composition range have been investigated by X-ray diffraction and Mössbauer effect measurements. Alloys with x less than 0.55 are bec, whereas those with x>0.9 are fce, in between, the samples are amorphous. The Mössbauer spectra at 300 K for the bce alloys with x<0.5 consist of a broadened sextet and the spectra for the alloys with x≥0.5 are quadrupole-split doublets with a slight asymmetry. The magnetic hyperfine field at 4.2 K decreases monotonically with Al concentration from 340 kOe in pure Fe to zero at x=0.7. The isomer shift increases essentially linearly with Al concentration, and reaches a maximum at x=0.75. It is noted that at the boundary of x=0.55 separating the bce and the amorphous states, there is no discernible change in elther hyperfine field or lsomer shift.     

非晶态NbNi合金的双居里点现象

在非晶态Nb_1-xNi_x(x=0.564,0.598,0.65)合金的低场交流磁化率中,既观察到巡游电子磁性的双居里点现象,又看到x=0.598,0.65这两个样品在低温端还出现自旋玻璃冻结的典型的磁化率尖峰。在这个合金系统中巡游电子磁性和局域磁矩的表现都很明显。 关键词：     

The effect of Si content on the martensitic transfor-mation temperature of Ni55.5e18Ga26.5-xSix alloys

This paper investigates the effects of substitution of Si for Ga on the martensitic transformation behaviours in Ni-Fe-Ga alloys by using optical metallographic microscope and differential scanning calorimetry (DSC) methods. The structure type of Ni_55.5Fe₁₈Ga_26.5-xSi_x alloys is determined by x-ray diffraction (XRD), and the XRD patterns show the microstructure of Ni-Fe-Ga-Si alloys transformed from body-centred tetragonal martensite (with Si content x = 0) to body-centred cubic austenite (with x = 2) at room temperature. The martensitic transformation temperatures of the Ni_55.5Fe₁₈Ga_26.5-xSi_x alloys decrease almost linearly with increasing Si content in the Si content range of x ≤ 3. Thermal treatment also plays an important role on martensitic transformation temperatures in the Ni-Fe-Ga-Si alloy. The valence electronic concentrations, size factor, L2₁ degree of order and strength of parent phase influence the martensitic transformation temperatures of the Ni-Fe-Ga-Si alloys. An understanding of the relationship between martensitic transformation temperatures and Si content will be significant for designing an appropriate Ni-Fe-Ga-Si alloy for a specific application at a given temperature.     

MAGNETIC PROPERTIES AND CRYSTALLIZATION OF THE RAPIDLY QUENCHED (Fe1-xNdx) 81.5B18.5 ALLOYS

Magnetic properties and crystallization behaviors of amorphous (Fe_1-xNd_x) _81.5B_18.5 alloys were studied. The crystallization temperature is found to rise at first and then drop monotonically with x, having a maximum value of 976K at x=0.11 (9at% Nd). The (Fe_1-xNd_x) _81.5B_18.5 alloys prepared at a quenching rate of v_s = 6.6m /s are amorphous, and exhibit good glass formability. Both the coercive field H_c and energy product (BH)_max depend strongly on Nd concentration. Amorphous (Fe_1-xNd_x) _81.5B_18.5 alloys with higher Nd concentration have a high coercive field at low temperature, due to the large random uniaxial anisotropy of Nd. The room-temperature H_c and (BH)_max obtained on optimal annealing con-ditions show two maxima as a function of Nd concentration x. The highest room-temperature coercive field H_c =22 kOe within the Nd concentrations around x=0.368 and the maximum energy product(RH)_max= 13.3 MG·Oe at x =0.055 are observed. The hard magnetic properties of these crystallized samples are related to the presence of the bard magnetic Nd₂Fe₁₄B phase.     

Influence of composition of the near-surface graded-gap layer on the admittance of metal-insulator-semiconductor structures based on graded-gap MBE n-Hg1−xCdxTe in wide temperature range

Influence of the CdTe content in a near-surface graded-gap layer on the admittance of MIS-structures fabricated on the basis of heteroepitaxial Hg_1?xCd_xTe (x = 0.22–0.23 and 0.31–0.32) films grown by molecular beam epitaxy was investigated in a wide temperature range. It is shown that a temperature drop from 77 K to 8 K results in a decrease of hysteresis of the capacitance-voltage (C-V) characteristics and a decrease of frequencies which corresponds to a high-frequency behaviour of C-V characteristics of MIS-structures based on n-HgCdTe (x = 0.22–0.23) with and without graded-gap layersand also for MIS-structures based on n-HgCdTe (x = 0.31–0.32). Temperature dependences of the resistance of the epitaxial film bulk and differential resistance of the space-charge region (SCR) in strong inversion mode were studied. The experimental results can be explained by the fact that for MIS-structures based on n-HgCdTe (x = 0.22–0.23) with the graded-gap layers and for MIS-structures based on n-HgCdTe (x = 0.31–0.32), the differential resistance of SCR is limited by Shockley-Read generation at 25–77 K. Differential resistance of SCR for MIS-structures based on n-HgCdTe (x = 0.22–0.23) without the graded-gap layers is limited by tunnelling through deep levels at 8–77 K.     

Ce2-xDyxFe17合金的磁熵研究

研究了Ce_2-xDy_xFe₁₇(x=0.0,0.3,0.5,1.0)系列合金在77—298K温区范围磁熵变,发现Ce_2-xDy_xFe₁₇系列合金有较大的磁熵变,居里温度可通过离子替代而改变,是一种可供选择的室温磁致冷材料.     

Au1-xNix合金(x=0.30-0.42)低温电阻率极小值的机理探讨

为了解释Au_1-xNi_x合金(x=0.30—0.42)低温出现电阻率极小值的实验结果,本文提出一个低浓度自旋集团顺磁态合金的模型,得到自旋集团孤立近似下和自旋集团耦合作用下的电阻率公式,并和晶格散射的贡献(由Au₈₀Ni₂₀合金或Au-Cu合金的ρ_i(T)实验数据代替)联合起来,得到ρ(T)的计算曲线,和实验结果符合得很好。当Tmin,电阻率随温度增高而下降,主要是自旋集团孤立近似下的Kondo效应引起的。自旋集团之间的RKKY耦合作用对电阻率的贡献在低温时大,随着温度增高按1/T规律迅速减小,所以ρ(T)-ρ_i(T)实验值在相当宽温度范围出现logT关系。随着温度增高,晶格散射对电阻率的贡献将变得重要,当T=T_min,电阻率出现极小值。 关键词：     

Metastable (GaSb)(1−x)(Sn2)x alloys: Crystal growth and phase stability of single crystal and polycrystalline layers

Single-phase metastable (GaSb)_(1−x)(Sn₂)_x alloys with x ⩽ 0.23 far exceeding the equilibrium solid solubility limit of x ⪅ 0.02 for Sn in GaSb, have been grown by rf sputter deposition. The key feature allowing the growth of single phase alloys was the use of low energy ion-bombardment-induced collisional mixing during deposition. Films grown at elevated temperatures T_s on GaAs(100) substrates were found to be single crystals while polycrystalline films with very strong (220) perferred orientation and grain sizes of 20–40 nm were obtained on amorphous glass substrates. The maximum film growth temperatures T_m at which single phase films could be obtained was a function of the negative substrate potential V_s during deposition and the composition x. For V_s = 75 V, T_m ranged from 375 °C at x = 0.06 to 125 °C at x = 0.23. Crystal growth and post-annealing studies both indicated that the transformation from the single-phase metastable state to the equilibrium (GaSb + βSn) state occurs through a continuous set of metastable GaSb-rich phases and that Sn precipitates out first in the α-diamond structure and then transforms to the β-tetragonal structure. In single crystal films, the GaSb-rich phase precipitates out coherently with the alloy matrix. The activation energy for phase separation ranged from ∼ 1.4 eV for alloys with x = 0.06 to 0.9 eV at x = 0.23. A phase map for crystal growth, plotted as a function of T_s and x, and an annealing transformation diagram for (GaSb)_0.86(Sn₂)_0.14 was determined.