The Electric Field Gradients in (Zr/Hf)Al3 and (Zr/Hf)2Al3 Intermetallic Compounds Studied by 181Ta- and 111Cd-PAC Spectroscopy

The electric quadrupole hyperfine interactions for ¹⁸¹Hf/¹⁸¹Ta and for ¹¹¹In/¹¹¹Cd probes in polycrystalline ZrAl₃ and Zr₂Al₃ compounds were measured in the temperature range 30–1100 K and compared with the results for isostructural hafnium aluminides. On the basis of the similarities of the numbers, sizes and asymmetries of electric field gradients, lattice site allocations were made. In all matrices, ¹⁸¹Hf/¹⁸¹Ta was found to substitute the Hf/Zr site. The ¹¹¹In/¹¹¹Cd impurities were also assigned to the Hf/Zr site in the compounds (Zr/Hf)Al₃, but appear to substitute the two non-equivalent Al sites in the Zr₂Al₃ and Hf₂Al₃ phases. This revised version was published online in September 2006 with corrections to the Cover Date.     

Influence of heat treatment on the structure and magnetic properties of the Co/Zr and Co/Hf multilayer amorphous films

The influence of annealing on the structure and magnetic properties of amorphous Co/Zr and Co/Hf multilayer films was studied with particular attention to the dependence of the magnetic properties, thermal stability and crystallization process on layer composition and thickness. The temperature at which crystallization commences increases from 400 to 460 °C as the layer thickness d_Zr or d_Hf increases from 6 to 18 Å, and decreases from 450 to 400 °C as d_Co increases from 12 to 18 Å. Multilayers containing 19–60 at% Zr were studied. The specific magnetization was found to increase even below the temperature at which crystallization commences. Our data are compared with non-multilayer Co–Zr amorphous films and rapidly quenched metallic glasses.     

Proximity effect in Nb/Zr multilayers with variable Nb/Zr ratio

We have investigated the effect of varying the individual layer thickness on the superconducting transition temperature (T_C) of Nb/Zr multilayers. These thin film multilayer structures were deposited using UHV magnetron sputtering with layer thickness ranging from 0.5 to 8 nm. In conformity with the predictions of the de Gennes equations in the Cooper limit (layer thickness small compared to coherence length), we find that the T_C increases with increasing thickness of the Nb layer (when the Zr layer thickness is constant), and decreases with increasing thickness of the Zr layer (when the Nb layer thickness is constant). The possible effect of the existence of an interfacial Nb-Zr layer is discussed. We also point out the marked influence of the in-plane grain dimension on the T_C in these multilayers.     

The effect of a nonmagnetic Zr layer on the magnetic and magneto-optical properties of Fe/Zr and Fe/Zr/Fe thin-film systems

The magnetic and magneto-optical properties of nanocrystalline Fe/Zr and Fe/Zr/Fe thin-film systems have been studied using the magneto-optical method. The strong effect of Zr layer thickness t _Zr on the magnetic properties of Fe/Zr samples was discovered. It was found that the value of the saturation field of the Fe/Zr/Fe systems oscillates as a function of t _Zr, which is explained by the oscillating character of the exchange interaction between ferromagnetic layers via a Zr spacer with the change in t _Zr. It was established that the values of the transverse Kerr effect depend on the thicknesses of both magnetic and nonmagnetic layers.     

Electric field gradients at Ta in Zr and Hf inter-metallic compounds

Here we calculate the electric field gradient (EFG) at the nucleus of the substitutional Ta impurity site in Zr₂T and Hf₂T (T=Cu, Ag, Au, and Pd) C11_b inter-metallic compounds. We use the ab initio FP-LAPW method as embodied in the Wien97 code in a super-cell approach and include lattice relaxations around the impurity. Our results are compared with EFG values inferred from measurements of the quadrupole coupling constants at the ¹¹¹Ta probe in these compounds performed with the time differential perturbed angular correlation (TDPAC) technique. We also performed EFG calculations for the pure inter-metallic compounds. Through the comparison of theoretical and experimental EFGs in these cases, we elucidate the role played by the Ta probe in the TDPAC measurements of Hf and Zr compounds. Our results show that, although the EFGs at the Hf site are very similar to the EFGs at the Ta impurity, there is no direct correlation between the Zr and Ta EFGs.     

四元硫化物Cu2Zn(Ti,Zr, Hf)S4:一类新颖光伏材料

采用第一性原理电子结构方法研究了四价过渡金属Ti, Zr和Hf替代Cu₂ZnSnS₄(CZTS)中Sn原子以及Se替代S原子所得到的四元硫族化合物的电子结构、光学性质和晶体结构的稳定性. 实验上用Se替代CZTS中部分S得到的Cu₂ZnSnS_4-xSe_x(CZTSSe)作为光吸收材料, 可以进一步提高光伏效率. 我们计算表明用Se替代S后, CZTSe的价带顶明显下移, 并接近Cu(In, Ga) Se₂ (CIGS)价带顶位置. 与CZTSe的电子结构特征一样, Cu₂Zn(Ti, Zr, Hf)S₄四元硫化物的价带顶与母体材料CZTS相比也向低能移动, 并接近CIGS价带顶位置. 由于高光伏效率要求窗口材料ZnO、缓冲层材料和光吸收材料的价带顶和带隙满足一定的渐进的变化关系, 因此可以预见用Cu₂Zn(Ti, Zr, Hf)S₄作光吸收材料可以有效地提高甚至接近CIGS的光伏效率. 通过计算弹性常数和声子谱, 以及有限温度下第一性原理分子动力学模拟, 发现Cu₂Zn(Ti, Zr, Hf)S₄的结构稳定性与CZTS相近. 进一步计算Cu₂Zn(Ti, Zr, Hf)S₄与不同缓冲层间和窗口材料与缓冲层间的反射系数, 并讨论了ZnSe, In₂S₃, ZnS作为缓冲层材料和TiO₂作为窗口材料对光伏效率可能的影响.     

Ti1－x(Hf0.919Zr0.081)xNiSn的制备及热电性能

采用固相反应法合成了单相的Ti_1-x(Hf_0.919Zr_0.081) _xNiSn (x＝0.00—0.15)，并用放电等离子烧结方法制备出密实块体材料. 研究 了Hf和Zr同时在Ti位上的等电子合金化对Ti基半Heusler化合物热电性能的影响规律. 结果 表明：少量的Hf和微量的Zr在Ti位上的等电子合金化，显著地降低了体系的热导率κ，同时 显著地提高了体系的Seebeck系数α. 组成为Ti_{0.85关键词： 半Heusler 固相反应 热电性能}     

The first principle study of magnetic properties of Mn2WSn,Fe2YSn (Y=Ti,V), Co2YSn (Y=Ti,Zr, Hf,V, Mn) and Ni2YSn (Y=Ti,Zr, Hf,V, Mn) heusler alloys

The spin polarized electronic band structures, density of states (DOS) and magnetic properties of Mn₂WSn, Fe₂YSn (Y=Ti, V), Co₂YSn (Y=Ti, Zr, Hf, V, Mn) and Ni₂YSn (Y=Ti, Zr, Hf, V, Mn) huesler compounds are reported. The calculations are performed by using full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory. The magnetic trend in these compounds is studied using values of magnetic moments, exchange interaction and calculated band gap. The results reveal that Mn₂WSn and Ni₂VSn show 100% spin polarization, Co₂YSn (Y=Ti, Zr, Hf, Mn), Fe₂YSn (Y=Ti, V), and Ni₂MnSn exhibit metallic nature and Ni₂YSn (Y=Ti, Zr, Hf) and Co₂VSn show semi-conducting behavior.     

M@C28(M=Ti,Zr,Hf)内裹配合物的电子结构及其稳定性

用B3-LYP赝势模型的密度泛函理论,对M@C₂₈(M=Ti,Zr,Hf)内裹配合物电子结构进行从头计算研究.计算包括确定稳定的几何结构参量的分子几何结构进行优化和自然键轨道分析.结果发现Ti与C₂₈基团的相互作用明显不同于Zr(Hf)与C₂₈的相互作用,表现在原子的电子组态、成键特征和电子态分布等诸多方面.另外,结合能估算表明,这三种内裹配合物均能稳定存在,但Zr@C₂₈和Hf@C₂₈比Ti@C     

Hf3Al2 and Zr3Al2 Isostructural Aluminides Studied by PAC with 181Ta and 111Cd Probes

The electric quadrupole hyperfine interactions for ¹⁸¹Hf/¹⁸¹Ta and for ¹¹¹In/¹¹¹Cd probes in polycrystalline Zr₃Al₂ and Hf₃Al₂ compounds were measured in the temperature range 24–1100 K. The hyperfine quadrupole interaction parameters were determined after different doping techniques and heat treatments of the samples.¹⁸¹Hf/¹⁸¹Ta was found to substitute the Hf/Zr sites and the ¹¹¹In/¹¹¹Cd impurities appear to substitute both the 8(j) Al sites and the three nonequivalent Hf/Zr sites.     

Effects of Zr impurity on microscopic behavior of Hf metal

Hf metal with ∼ 3 wt% Zr impurity has been reinvestigated by perturbed angular correlation (PAC) spectroscopy using a LaBr₃(Ce)–BaF₂ detector set up to understand the microscopic behavior of this metal with temperature. From present measurements, five quadrupole interaction frequencies have been found at room temperature where both pure hcp fraction (∼33%) with 12 nearest neighbor Hf surrounding the probe ¹⁸¹Hf atom and the probe–impurity fraction (∼33%) corresponding to 11 nearest neighbor Hf plus one dissimilar Zr atom are clearly distinguished. At room temperature, the results for quadrupole frequency and asymmetry parameter are found to be ω_Q=51.6(4) Mrad/s, η=0.20(4) for the impurity fraction and ω_Q=46.8(2) Mrad/s, η=0 for the pure fraction with values of frequency distribution width δ=0 for both components. At 77 K, only 1 NN Zr impurity (∼93%) and pure hcp (∼7%) components have been found with a value of δ ∼ 10% for the impurity fraction. A drastic change in microstructural configuration of Hf metal is observed at 473 K where the impurity fraction increases to ∼ 50% and the pure hcp fraction reduces to ∼ 15% with abrupt changes in quadrupole frequencies for both components. The pure fraction then increases with temperature and enhances to ∼50% at 973 K. In the temperature range 473–973 K, quadrupole frequencies for both components are found to decrease slowly with temperature. Using the Arrhenius relation, binding energy (B) for the probe–impurity pair and the entropy of formation are measured from temperature dependent fractions of probe–impurity and pure hcp in the temperature range 473–773 K. The three other minor components found at different temperatures are attributed to crystalline defects.     

Lattice instabilities and superconductivity of (Hf,Zr) V2 compounds

The temperature dependences of the sound velocity of the pseudobinary (Hf, Zr)V₂ compounds show the evidence of lattice instability. The inverse relation between the superconducting transition temperature and the deduced transformation temperature is shown.     

Gap at the Fermi level in the intermetallic vacancy system RBiSn(R=Ti,Zr,Hf)

The new class of intermetallic compounds RNiSn(R=Ti,Zr,Hf) may be characterised by the presence of an ordered sublattice of Ni atom vacancies in comparison with normal metals RNi₂Sn with no Ni vacancies. We report unusual transport and optical properties of the RNiSn system. The electrical resistivity of RNiSn is very high (3<p<100) mOhm*cm; the temperature coefficient of resistivity (TCR) is negative and strongly dependent on the annealing conditions. For some samples ZrNiSn and for a single crystal of TiNiSn the resistivity can be described by the Mott's law at temperatures 0.1<T<20 K. A phase transition nearT=100 K without change of crystal structure was deduced from Hall effect data and the temperature dependence of the lattice constant. Preliminary data on transport phenomena in RPtSn and RPdSn(R=Ti,Zr,Hf) compounds are also reported. The unusual properties of RNiSn system might be related to a gap of the electron spectrum near the Fermi energy.     

Zr and Hf microalloying in an Al–Y–Fe amorphous alloy. Relation between local structure and glass-forming ability

The effects of the addition of small amounts of Zr and Hf (0.5–3%) on the atomic structure of Al₈₈Y₇Fe₅ metallic glass were examined from extended X-ray absorption fine structure (EXAFS) experiments to better understand the influence of these microadditions on the glass-forming ability of this alloy. Measurements at the Zr K and Hf LIII absorption edges allowed the local structures around Zr and Hf atoms to be determined. The same Al environment was found for the different concentrations, consisting of a small cluster extending up to 4.5 Å around the Zr atoms and up to 6 Å around the Hf ones. Although the clustering effect is smaller in the Zr neighbourhood, a drastic shortening of the nearest Zr–Al distance is shown, providing evidence for some covalent character to the bonding, in line with the increased glass-forming ability found in the alloys made with the Zr microaddition.     

Zr粉粒径对Zr/KClO4烟火剂燃烧特性的影响

 研究了烟火药激光器泵浦源传统配方Zr/KClO₄中Zr粉粒径对该配方燃烧特性的影响。结果表明：Zr粉从61.375 μm减小到18.675 μm,Zr/KClO₄混合物的点火温度从506.40 ℃降低到492.42 ℃,燃烧辐射脉宽由60 ms缩短到25 ms,峰值辐射强度增加1倍;在 200～1 100 nm波段内,随着Zr粉粒径的减小,可见光区内的辐射能所占的比例增强;针对掺钕激光介质的泵浦而言,Zr粉粒径为800目时,分布在激光介质的3个主要泵浦带内的辐射能最高,而且闪光脉宽最短。因此,在其它条件相同时,选择颗粒尺寸小的Zr粉有利于获得高的激光输出。     

Ab initio investigation into the structural, electronic and elastic properties of AlCu2TM (TM = Ti, Zr and Hf) ternary compounds

The Al-Cu-TM (TM = transition metal) alloy system has attracted great attention for both excellent glass-forming ability and its interesting physical properties. In this work, an investigation into the crystal, electrical and elastic properties of the AlCu₂TM (TM = Ti, Zr, and Hf) compounds has been conducted by first-principles calculations based on density-functional theory. The fully relaxed structure parameters of the AlCu₂TM compounds are in good agreement with previous experimental and other theoretical results. Besides, the cohesive energies of all the AlCu₂TM compounds have been evaluated. The energy band and densities of state of these compounds are also obtained. According to the calculated single crystal elastic constants, all the compounds are mechanically stable. The polycrystalline bulk moduli, shear moduli, Young’s moduli and Poisson’s ratio have been deduced by using Voigt-Reuss-Hill (VRH) approximations. The calculated negative Cauchy pressure and ratio of bulk modulus to shear modulus indicated that the AlCu₂TM compounds are ductile materials. The Debye temperatures of the AlCu₂TM compounds decrease with increasing the TM (Ti, Zr, and Hf) atomic number.     

The interaction of D2O with Zr(0001) at 80 K

The adsorption of D₂O on Zr(0001) at 80 K and its subsequent reactions at higher temperatures have been studied by thermal desorption spectroscopy (TDS), work-function measurements (Δф), nuclear reaction analysis (NRA), LEED, infrared reflection spectroscopy (FTIR-RAS), Auger electron spectroscopy (AES), and static secondary ion mass spectroscopy (SSIMS). D₂O adsorption on Zr(0001) at 80 K is accompanied by a Δф of −1.33 eV. The adsorbed D₂O can be characterized into three layers by TDS: a chemisorbed layer (up to 0.23 ML), a second adsorbed layer, and an ice layer. The chemisorbed D₂O dissociates into OD_ad and D_ad at 80 K (possibly also into O_ad) and no desorption products could be detected, implying that the reaction products dissolved into the zirconium at temperatures appropriate for each component. The ice layer and most of the second adsorbed layer desorb as molecular water during heating. The water adsorbed at 80 K did not form any long-range ordered structure, but a (2 × 2) LEED pattern that was formed by heating the sample to temperatures above 430 K is believed due to be an ordered oxygen superstructure.     

Magnetic behavior of Pr1 − xMxCo5 compounds (M = Ti, Zr and Hf)

Magnetic characteristics of Ti-, Zr- and Hf-substituted PrCo₅ alloys have been studied over the temperature range from 77 to 300 K and for applied fields up to 20 kOe. It is established that Ti, Zr and Hf substitute for Pr. Single-phase materials are formed for all values of x up to 0.2 in the system Pr_1−xZr_xCo₅ but for x only up to 0.1 for Pr_1−xTi_x Co₅ and Pr_1−xHfxCo₅ alloys. Larger amounts of Zr can be substituted if the material is made hyperstoichiometric in Co, e.g., Pr_0.7Zr_0.3Co_5.5. All the alloys show a decrease in magnetic moment and an increase in Curie temperature as x increases. Anisotropy fields decrease as x increases at 295 K. Anomalous behavior is observed at 77 K, suggested that these ternary alloys may have a cone structure at this temperature.     

Surface phenomena of HA/TiN coatings on the nanotubular-structured beta Ti-29Nb-5Zr alloy for biomaterials

Surface phenomena of HA/TiN coatings on the nanotubular-structured beta Ti-29Nb-5Zr alloy for biomaterials have been investigated by several experimental methods. The nanotubular structure was formed by anodizing the Ti-29Nb-5Zr alloy in 1 M H₃PO₄ electrolytes with 1.0 wt.% NaF at room temperature. Hydroxyapatite (HA)/titanium nitride (TiN) films were deposited on Ti-29Nb-5Zr alloy specimens using a magnetron sputtering system. The HA target was made of human tooth-ash by sintering at 1300 °C for 1 h, and the HA target had an average Ca/P ratio of 1.9. The HA/TiN depositions were performed, using the pure HA target, on Ti-29Nb-5Zr alloy following the initial deposition of a TiN buffer layer coating. Microstructures and nanotubular morphology of the coated alloy specimens were examined by FE-SEM, EDX, XRD, and XPS. The Ti-29Nb-5Zr alloy substrate had small grain size and preferred orientation along the drawing direction. The HA/TiN coating was stable with a uniform morphology at the tips of the nanotubes.     

Influence of milling time on the structural, microstructural and magnetic properties of mechanically alloyed Ni58Fe12Zr10Hf10B10 nanostructured/amorphous powders

This paper investigates structural, microstructural and magnetic properties of amorphous/nanocrystalline Ni₅₈Fe₁₂Zr₁₀Hf₁₀B₁₀ powders prepared by high energy milling. Ball milling of Ni, Fe, Zr, Hf and B leads to alloying of the element powders at 120 h. The results show that at 190 h the amorphous content is at the highest level and the grain size is about 2 nm. The magnetic measurements reveal that the coercivity and the saturation magnetization reach about 20 Oe and 30 emu/g at 190 h and become approximately 5 Oe and 40 emu/g after a suitable heat treatment, respectively.