Zr Layer Research Articles

Improving the polarization switching properties of wurtzite AlN by introducing IV–IV/AlN superlattice and P-doping

The large coercive electric field is the main obstacle for the application of wurtzite ferroelectrics in the memory devices. To explore the effective methods to reduce the coercive electric field of wurtzite ferroelectrics, in this work, after screening a series of possible candidates, (MC)1/(AlN)n (M = Ti, Zr) superlattices and anion P-doping are both chosen to regulate the switching energy barrier of wurtzite AlN based on the density functional theory calculations. It is found that the polarization switching energy barriers of wurtzite AlN gradually decrease by increasing the ratio of the MC (M = Ti, Zr) layer. When the ratio of the MC layer is up to 33%, the polarization switching energy barriers of (TiC)1/(AlN)n and (ZrC)1/(AlN)n are decreased by 68% and 55%, respectively, compared with that of pure wurtzite AlN. The anionic P-doping in AlN results in a 48% lower energy barrier. Also, the ferroelectric polarization in the designed superlattices and P-doped AlN is well maintained compared to pure AlN. Thus, the results show that the (MC)1/(AlN)n (M = Ti, Zr) superlattices and anion P-doping approaches are effective in improving the polarization switching properties of wurtzite AlN.

Radiation damage in He irradiated nanolayered Zr/Nb at different temperatures

Nanolayered Zr/Nb metals are considered promising for advanced nuclear reactors due to their superior resistance to irradiation. In this study, Zr/Nb multilayers were irradiated with 50 keV He+ ions to a fluence of 1 × 1017 ions/cm2 at temperatures of room temperature, 350 °C, and 500 °C to investigate irradiation-induced structural changes. X-ray diffraction (XRD) analysis indicated low-angle shifts of 0.08-0.54° and high-angle shifts of 0.08-0.42° in the irradiated Zr and Nb layers, suggesting tensile and compressive strains, respectively. At 500 °C, the selected-area electron diffraction (SAED) observed a 9.2% lattice expansion in Zr and a 0.13% contraction in Nb. Geometric phase analysis (GPA) revealed varying strain distributions, transitioning from incoherent to coherent interfaces with increasing irradiation damage. Transmission electron microscopy (TEM) identified the presence of He bubbles in the Zr layer as one of the reasons for strain differences. Nanoindentation tests showed an increase at a depth of 150 nm hardness of 0.831 GPa at 500 °C compared to 350 °C. These results are attributed to differences in crystal structure, vacancy dynamics, interfacial effects, and lattice strain influences. Stability of Zr/Nb interfaces after He irradiation was studied. This study provides insights into the radiation behavior of Zr/Nb nanoscale metallic materials, enhancing our understanding of their potential as structural materials in nuclear energy systems.

Optimized designation of mesoscopic configuration of Zr/Ti layered metal composites for strength-ductility synergy improvement

Zirconium (Zr) and its alloys are highly promising for extreme service environments due to their excellent radiation and corrosion resistance. However, a major challenge in Zr-based materials lies in the strength-ductility trade-off, which limits their broader structural applications. This study aims to address this challenge by fabricating Zr/Ti layered metal composites (LMCs) with different layer thickness ratios (LTRs) and investigating the effects of LTR on the mechanical properties of Zr/Ti LMCs. Zr/Ti LMCs with varying LTRs were fabricated to explore how mesoscopic configurations influence their deformation mechanisms. The results reveal that an optimized layer thickness (∼50 μm for Zr and ∼40 μm for Ti) maximizes the hetero-deformation-induced (HDI) strengthening effect, resulting in a synergy improvement in strength and ductility. Stable and constrained cracks observed in the Zr layers contributed to local stress relief and improved ductility. The anisotropic deformation between the Zr and Ti layers transformed the local stress states into triaxial states. In addition, the localized stress state and inter-layer strain transmission also promote prismatic <a> slip near the interfaces. This study provides key insights into the design of Zr-based composites with improved mechanical performance, offering potential solutions for their application in demanding environments.

Adhesion layers between piezoelectric and magnetostrictive layers in a MEMS magneto-sensor stack: Influence on the phase transformation of deposited Co/Fe multilayers to magnetostrictive CoxFe1−x phase

Magnetoelectric MEMS devices, such as magnetic field sensors, may be composed of a multilayer stack as a magnetostrictive layer, which is mechanically coupled to a piezoelectric film. Good adhesion and a stable rigid interface have to be maintained for such a sensor. Certain electric and magnetic properties, especially the magnetostriction, have to reach sufficiently high values, which can be achieved by selected phases or mixtures of phases. In this study, Co/Fe multilayers with varied bilayer periods are deposited onto AlN or Sc0.14Al0.86N coated Si substrates by DC magnetron sputtering with the optional insertion of a 5 nm thick adhesion layer of Cr or Zr to investigate its influence on the formation of the desired mixture of bcc and fcc Co0.7Fe0.3 phases, which are expected to yield a high magnetostrictive strain, after an RTA at 800 °C. A qualitative phase analysis is made by XRD in Bragg-Brentano geometry and shows that the bcc + fcc mixture can be achieved with a Cr interlayer. A sharp, void free, and undamaged interface for that case was observed in SEM images of cross sections prepared with FIB.

Effect of diffusion barriers on steam oxidation properties and interface evolutions of Cr coating for zirconium alloy at 1200 °C

Currently, Cr-based coatings are considered the most promising protective coatings for zirconium alloy claddings under the ATF design concept. However, the primary factor affecting the oxidation resistance of Cr coatings is the interdiffusion of Cr and Zr. In this study, Cr coatings with three refractory metal interlayers of Nb, Mo, and Ta were deposited on zirconium alloy surfaces using closed-field unbalanced magnetron sputtering. The study investigated the effects of different interlayers on the microstructure, oxidation properties, and interface evolution process of Cr coatings under steam conditions at 1200 ℃, and compared them with Cr coatings without intermediate layers. The results indicate that the refractory metal interlayer influences the orientation and growth rate of Cr coating grains. The formation of a Laves phase mixed layer in the interlayer during oxidation effectively hinders the diffusion of O and Cr to the zirconium alloy matrix, enhancing its oxidation resistance. Furthermore, the diffusion rate and vacancy concentration of Mo and Ta elements to the Zr layer exceed that of diffusion to the Cr layer. During the cooling process, a precipitate phase forms in the Zr-4 matrix, while the Nb coating forms an infinite solid solution in the β-Zr.

Microstructural evolution in a one-directional phase transforming ultrahigh temperature ceramic laminate composite

A metal-ceramic multilayer composite composed of Zr and ZrC films was magnetron sputter deposited and annealed at 1325 °C to demonstrate its ability to phase transform into a single phase, substoichiometric ultrahigh temperature ceramic carbide. The pre-annealed laminate microstructure comprised columnar grains for both the Zr and ZrC layers, common to thin film deposition. Upon annealing, the diffusion of carbon facilitated the precipitation of multiple equiaxed carbide grains that consumed the former Zr layers. As this carbon diffused from ZrC, it resulted in the carbide undergoing a lattice contraction where the elastic strains facilitated a decohesion between the carbide grain boundaries. This decohesion is shown to be mitigated by increasing the ratio of the initial ZrC layer-to-Zr layer thicknesses. Finally, oxygen, found to be a minor impurity in the ethylene hydrocarbon gas used to reactively deposit ZrC, facilitated irregular zirconia precipitation within the evolving microstructure during the anneal.

Design and analysis of a planar and multilayer metamaterial with the dual-functions of an ultra-broadband and high absorptivity absorber and a multi-wavelength resonator

This absorber exhibits a hierarchical structure, featuring layers of ZnO, Zr, yttria-stabilized zirconia (YSZ), Zr, YSZ, Al, YSZ and Al from top to bottom. Simulation analyses were conducted using COMSOL Multiphysics® simulation software (version 6.1). The primary innovation of this multilayer metamaterial lies in its entirely planar configuration, enabling switchable functionality: one ultra-broadband with high absorptivity (facilitated by the ZnO layer) and three narrowband absorption peaks (achieved through the Al layer). The simulation results clearly demonstrate that when light was incident from the ZnO direction onto this designed structure, the investigated planar and multi-functional absorber exhibited excellent absorber characteristics. Over an ultra-wide broadband range from 395 to 2070[Formula: see text]nm, the average absorptivity reached an impressive 95.03%. When light was incident from the Al direction onto the investigated planar and dual-functional absorber, three narrowband absorption peaks were observed at wavelengths 355, 550 and 1200[Formula: see text]nm. The second innovation highlights the effectiveness of ZnO as an anti-reflection layer, elevating the absorptivity of the ultra-broadband absorber. The third innovation establishes that Al is the optimal metal choice. It is worth noting that while using no Al layer or substituting Al with other metals did not diminish the absorptivity of the ultra-broadband absorber, alternative metals might adversely affect the absorptivity of the multi-wavelength absorber.

Hydrogen-Induced Microstructure Changes in Zr/Nb Nanoscale Multilayer Structures

Zr/Nb nanoscale multilayer coatings (NMCs) were studied after hydrogenation in a gaseous environment at 400 °C. The hydrogen distribution and content were determined by pressure and hydrogenation time. Increasing the pressure from 0.2 to 2 MPa resulted in different hydrogen distribution within the Zr/Nb NMCs, while the concentration remained constant at 0.0150 ± 0.0015 wt. %. The hydrogen concentration increased from 0.0165 ± 0.001 to 0.0370 ± 0.0015 wt. % when the hydrogenation time was extended from 1 to 7 h. The δ-ZrH hydride phase was formed in the Zr layers with Zr crystals reorienting towards the [100] direction. The Nb(110) diffraction reflex shifted towards smaller angles and the interplanar distance in the niobium layers increased, indicating significant lateral compressive stresses. Despite an increase in pressure, the nanohardness and Young’s modulus of the Zr/Nb NMCs remained stable. Increasing the hydrogen concentration to 0.0370 ± 0.0015 wt. % resulted in a 40% increase in nanohardness. At this concentration, the relative values of the Doppler broadening variable energy positron annihilation spectroscopy (S/S0) increased above the initial level, indicating an increase in excess free volume due to hydrogen-induced defects and changes. However, the predominant positron capture center remained intact. The Zr/Nb NMCs with hydrogen content ranging from 0.0150 ± 0.0015 to 0.0180 ± 0.001 wt. % exhibited a decrease in the free volume probed by positrons, as demonstrated by the Doppler broadening variable energy positron annihilation spectroscopy. This was evidenced by opposite changes in S and W (S↓W↑). The microstructural changes are attributed to defect annihilation during hydrogen accumulation near interfaces with the formation of hydrogen–vacancy clusters and hydrides.

Synthesis of BaZrS3 and BaS3 Thin Films: High and Low Temperature Approaches

Current research efforts in the field of the semiconducting chalcogenide perovskites are directed towards the fabrication of thin films and subsequently determine their performance in the photovoltaic application. These efforts are motivated by the outstanding properties of this class of materials in terms of stability, high absorption coefficient near the band edge and no significant health concerns compared to their halide counterparts. The approach followed here is to use stacked precursor layers and is adopted from other chalcogenide photovoltaic materials like the kesterites and chalcopyrites. The successful synthesis of BaZrS3 from stacked layers of BaS and Zr and annealing at high temperatures (~1100 °C) with the addition of elemental sulfur is demonstrated. However, the film shows the presence of secondary phases and a flawed surface. As an alternative to this, BaS3 could be used as precursor due to its low melting point of 554 °C. Previously, the fabrication of BaS3 films was demonstrated, but in order to utilize them in the fabrication of BaZrS3 thin films, their microstructure and processing are further improved in this work by reducing the synthesis temperature to 300 °C, resulting in a smoother surface. This work lays the groundwork for future research in the fabrication of chalcogenide perovskites utilizing stacked layers and BaS3.

Toward improving the performance of Cu2ZnSnS4-based solar cells with Zr, W or sulfurized layers at the SnO2:F/Cu2ZnSnS4 rear interface

The photovoltaic performance of Cu2ZnSnS4 (CZTS)-based thin film solar cells with transparent back contacts is mainly constrained by the ohmic loss due to degradation of the back contacts at high temperatures required for the growth of the CZTS absorbers. This work has attempted to use ultrathin Zr and W interlayers at the SnO2:F (FTO)/CZTS interface with the purpose of improving the ohmic properties of FTO and hence the performance of solar cells. 20 nm thick Zr and W layers were coated on FTO using direct current magnetron sputtering, followed by heating at 550 °C in a sulfur atmosphere for some of the samples. Inclusion of Zr and W interlayers compromised the transmittance of the FTO back contact, however heating of the samples in a sulfur atmosphere improved the transmittance to values comparable to or better than those of un-heated FTO. Furthermore, heated W/FTO showed a significant improvement in electrical conductivity as observed from Hall effect measurements. To make complete solar cells, CZTS absorber, buffer (CdS) and window (i-ZnO/ZnO:Al) layers were sequentially deposited on the un-heated FTO, Zr/FTO, W/FTO and Mo back contacts. Glow discharge optical emmision spectroscopy confirmed that Zr and W did not diffuse into the absorber and also prevented Na diffusion into the absorber. From the scanning electron microscopy cross sectional analysis, an impovement in the absober grain size and a clear junction between the absorber and FTO with W interlayer were observed. Grazing incident X-ray diffractometry confirmed the polycrystalline nature of the CZTS thin films and indicated the presence of other phases, particularly SnS2. On the resulting solar cell parameters, the inclusion of a W interlayer reduced the series resistance from 4.5 Ωcm to 3.7 Ωcm2. An improvement in short circuit current density (JSC) is also observed, enhancing the efficiency of the solar cells with CZTS/W/FTO to 3.1 % compared to that with CZTS/Mo at 2.7 % and CZTS/FTO at 3.0 %. W was found to improve the external quantum efficiency response and JSC of the solar cells for both backside and frontside light illumination. On the other hand, inclusion of a Zr interlayer (Zr/FTO) only slighlty improved the open circuit voltage, but compromised the JSC compared to FTO and W/FTO back contacts. Thus, the findings of this study demonstrate the prospect for improving the performance of the CZTS-based thin film solar cells through the inclusion of ultrathin Zr and W interlayers between the FTO back contact and CZTS absorber.

The effect of nanometre-scale kinetic competition on the phase selection in Zr/Si superstructure

Nano structured coating system demonstrates outstanding performance stemming from unique structure evolution. Zr/Si coating was proposed as an ideal candidate for the protection of Zr alloy cladding. However, the phase selection remains a challenge to coordinate the complex requirement under the service and accident conditions of reactor core. In this work, a phase selection mechanism for amorphous Zr-Si-O (abbr. ZSO) was elucidated by the competitive consumption of Zr layer by silicidation and oxidation, which was also scale-dependent. The energy-loss near-edge fine structure and nanoindentation were also employed to characterize the unique scale effect in the two processes. Both the oxides kinetics and elastic modulus gain indicated an immediate passivation process under the subcritical condition after the in situ phase selection of the amorphous ZSO. Ab initio molecular dynamics (AIMD) was performed to disclose the origination of depressed O migration in ZSO. The multilayer structure also shows accident tolerance potential. The interfacial phase selection provided a strategy to regulate mesoscale structure originating from nanomter interface and meets the diversified requirement for “structure-performance relationship” under the service and accident conditions.

The planar anodic Al2O3-ZrO2 nanocomposite capacitor dielectrics for advanced passive device integration

ABSTRACT The need for integrated passive devices (IPDs) emerges from the increasing consumer demand for electronic product miniaturization. Metal-insulator-metal (MIM) capacitors are vital components of IPD systems. Developing new materials and technologies is essential for advancing capacitor characteristics and co-integrating with other electronic passives. Here we present an innovative electrochemical technology joined with the sputter-deposition of Al and Zr layers to synthesize novel planar nanocomposite metal-oxide dielectrics consisting of ZrO2 nanorods self-embedded into the nanoporous Al2O3 matrix such that its pores are entirely filled with zirconium oxide. The technology is utilized in MIM capacitors characterized by modern surface and interface analysis techniques and electrical measurements. In the 95–480 nm thickness range, the best-achieved MIM device characteristics are the one-layer capacitance density of 112 nF·cm−2, the loss tangent of 4·10−3 at frequencies up to 1 MHz, the leakage current density of 40 pA·cm−2, the breakdown field strength of up to 10 MV·cm−1, the energy density of 100 J·cm−3, the quadratic voltage coefficient of capacitance of 4 ppm·V−2, and the temperature coefficient of capacitance of 480 ppm·K−1 at 293–423 K at 1 MHz. The outstanding performance, stability, and tunable capacitors’ characteristics allow for their application in low-pass filters, coupling/decoupling/bypass circuits, RC oscillators, energy-storage devices, ultrafast charge/discharge units, or high-precision analog-to-digital converters. The capacitor technology based on the non-porous planar anodic-oxide dielectrics complements the electrochemical conception of IPDs that combined, until now, the anodized aluminum interconnection, microresistors, and microinductors, all co-related in one system for use in portable electronic devices.

Amidoxime-Containing Zr and Hf Atomic Layer Deposition Precursors for Metal Oxide Thin Films.

In this article, we discuss the synthesis of eight novel zirconium and hafnium complexes containing amidoxime ligands as potential precursors for atomic layer deposition (ALD). Two amidoximes, viz., (E)-N'-hydroxy-N,N-dimethylacetimidamide (mdaoH) and (Z)-N'-hydroxy-N,N-dimethylpivalimidamide (tdaoH), along with their Zr and Hf homoleptic complexes, Zr(mdao)4 (1), Hf(mdao)4 (2), Zr(tdao)4 (3), and Hf(tdao)4 (4) were prepared. We further synthesized heteroleptic compounds with different physical properties by introducing cyclopentadienyl (Cp) ligand, namely, CpZr(mdao)3 (5), CpHf(mdao)3 (6), CpZr(tdao)3 (7), and CpHf(tdao)3 (8). Thermogravimetric analysis was used for the assessment of the evaporation characteristics of complexes 1, 2, 5, and 6, and it revealed multistep weight losses with high residues. On the other hand, the thermogravimetric analysis curves of complexes 3, 4, 7, and 8 comprising tdao ligands revealed single-step weight losses with moderate residues. Single-crystal X-ray diffraction studies of complexes 1, 3, and 7 showed that all of the complexes have monomeric molecular structures. Complex 7 exhibited a low melting point (75 °C), good volatility, and high thermal stability compared with other complexes. Therefore, an atomic layer deposition process for the growth of ZrO2 was developed by using ZrCp(tdao)3 (7) as a novel precursor.

Effect of Irradiation with a Pulsed Electron Beam on the Defect Structure Formation and the Properties of the Surface Layer of Zr–Nb–H System Alloys

Effect of Irradiation with a Pulsed Electron Beam on the Defect Structure Formation and the Properties of the Surface Layer of Zr–Nb–H System Alloys

Features of Helium-Vacancy Complex Formation at the Zr/Nb Interface.

A first-principles study of the atomic structure and electron density distribution at the Zr/Nb interface under the influence of helium impurities and helium-vacancy complexes was performed using the optimised Vanderbilt pseudopotential method. For the determination of the preferred positions of the helium atom, the vacancy and the helium-vacancy complex at the interface, the formation energy of the Zr-Nb-He system has been calculated. The preferred positions of the helium atoms are in the first two atomic layers of Zr at the interface, where helium-vacancy complexes form. This leads to a noticeable increase in the size of the reduced electron density areas induced by vacancies in the first Zr layers at the interface. The formation of the helium-vacancy complex reduces the size of the reduced electron density areas in the third Zr and Nb layers as well as in the Zr and Nb bulk. Vacancies in the first niobium layer near the interface attract the nearest zirconium atoms and partially replenish the electron density. This may indicate a possible self-healing of this type of defect.

Orbital torque originating from orbital Hall effect in Zr

We investigate current-induced torques generated by Zr. We show that the generation efficiency of the current-induced torque increases with increasing the thickness of the Zr layer in ${\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}/\mathrm{Zr}$ and Ni/Zr bilayers, which indicates that the observed current-induced torque originates from the bulk of the Zr layer. We find that the sign of the current-induced torques is opposite to that expected from the spin Hall effect but is consistent with that expected from the orbital Hall effect in the Zr layer. Furthermore, we find that the torque efficiency increases with increasing the thickness of the ferromagnetic layer, which is consistent with the prediction of long-range orbital transport in ferromagnets. These observations demonstrate that the orbital Hall effect in the Zr layer is the main source of the current-induced torque. This finding highlights the important role of orbital transport in generating current-induced torques, advancing the understanding of angular momentum dynamics in solid-state devices with $4d$ transition metals.

Microstructure analysis of Xe20+ irradiation and postirradiation corrosion of Zr-4 and Zr–1Nb alloys

The microstructure evolution of 5 MeV Xe20+ irradiation and the corrosion behavior of postirradiation in Zr-4 and Zr–1Nb alloys have been investigated. Positron results showed that vacancy defects, such as vacancies and vacancy clusters, are produced in Zr-4 and Zr–1Nb alloys after Xe20+ irradiation, and less vacancy defects are formed at 360 °C irradiation than at room temperature irradiation, resulting in lower S parameters due to recombination of defects. The nanoindentation results found that vacancy defects produced by irradiation lead to the hardening of both Zr-4 and Zr–1Nb alloys. Corrosion weight gain tests showed that the damaged layer induced by irradiation accelerates the oxidation rate during the corrosion process. Compared to the Zr-4 alloy, the damaged layer of Zr–1Nb alloy contains more vacancy defects after room temperature irradiation, which correspond to higher hardness increase and faster corrosion weight gain, resulting in the formation of cracks in oxide films as is observed by SEM. At the early stage of the corrosion, the postirradiation corrosion resistance of Zr-4 alloy may be better than that of Zr–1Nb alloy.

Measurement of local mechanical properties for Cr-coated accident tolerant fuel cladding

After the Fukushima accident, there has been motivation to develop accident tolerant fuel (ATF) cladding has been encouraged to meet increased need for safety under accident conditions. Many countries have focused on surface-modified Zr cladding such as Cr or Cr-Al alloy coated Zr-alloy cladding as a near-term application. In the case of coated cladding, there is no currently mechanical properties data measured by a traditional tensile test to describe the characteristics of coated layer directly due to its thin thickness. In this regard, we introduce small scale mechanical test techniques, nanoindentation tests and micro-pillar compression test, to evaluate the mechanical properties for thin coated layer. The results are presented for Cr-coated Optimized ZIRLOTM ATF claddings developed for a high oxidation resistance. From the small-scale tests, the mechanical behaviors including elastic modulus and yield strength were confirmed in both Cr and Zr layers. Their values were equivalent to that of bulk properties measured with conventional testing methods. This implies that the measured mechanical properties by the small-scale tests could represent the bulk properties and could be useful data for reliable fuel performance assessment for coated ATF cladding.

Surface-induced ferromagnetism and anomalous Hall transport at Zr2S(001)

Two-dimensional layered electrides possessing anionic excess electrons in the interstitial spaces between cationic layers have attracted much attention due to their promising opportunities in both fundamental research and technological applications. Using first-principles calculations, we predict that the layered bulk electride ${\mathrm{Zr}}_{2}\mathrm{S}$ is nonmagnetic with massive Dirac nodal-line states arising from $\mathrm{Zr}\text{\ensuremath{-}}4d$ cationic and interlayer anionic electrons. However, the ${\mathrm{Zr}}_{2}\mathrm{S}(001)$ surface increases the density of states at the Fermi level due to the surface potential, thereby inducing a ferromagnetic order at the outermost Zr layer via the Stoner instability. Consequently, the time-reversal symmetry breaking at the surface not only generates spin-polarized topological surface states with intricate helical spin textures but also hosts an intrinsic anomalous Hall effect originating from the Berry curvature generated by spin-orbit coupling. Our findings offer a playground to investigate the emergence of ferromagnetism and anomalous Hall transport at the surface of nonmagnetic topological electrides.

Effect of inserting the Zr layers on the tribo-corrosion behavior of Zr/ZrN multilayer coatings on titanium alloys

In this work, tribo-corrosion behavior of Zr/ZrN multilayer coatings in simulated body fluid (SBF) was investigated. The results indicated that Zr/ZrN-7 multilayer coatings possessed superior corrosion and tribo-corrosion resistance than the single ZrN coating. The effective inhibition of corrosive medium permeating by both forming a ZrO2 passive film and a multilayer structure contributed to the superior corrosion resistance. Furthermore, the improved corrosion, as well as suppressing crack propagation by the insertion of the Zr layer, enhanced the tribo-corrosion performance. Inserting Zr layers was found to be an effective method to improve the tribo-corrosion performance of Zr/ZrN multilayer coatings.