Zr 3d Research Articles

Synchrotron-based high-resolution photoemission spectroscopy study of ZIRLO cladding with H2O adsorption: Coverage and temperature dependence

The coverage and temperature dependence of ZIRLO cladding with H2O adsorption are studied using synchrotron-based high-resolution photoemission spectroscopy (HRPES). Based on the analytical results of the Zr 3d, O 1 s, C 1 s, and Sn 3d HRPES profiles prior to H2O adsorption, we determine the surface compositions of O2−, hydroxyl OH−, chemisorbed H2O, zirconium carbide, adventitious carbon, Sn metal, and SnO2 in ZIRLO. When ZIRLO is exposed to H2O molecules, the relative proportion of zirconium metal decreases, whereas that of the total zirconium oxides increases, suggesting the reaction between H2O and the zirconium metal in ZIRLO. On annealing a sample with 1000 L H2O on ZIRLO at 300 °C, Zr2O3 and ZrO2 decompose, and oxygen diffuses into the bulk, thereby reducing the oxidation states of zirconium on the surface. Moreover, at this temperature, the excess H2O molecules on ZIRLO are thoroughly desorbed and tin element is diffused into the bulk in ZIRLO.

Gas sensing nature and characterization of Zr doped TiO2 films prepared by automated nebulizer spray pyrolysis technique

This paper investigates the Zr doped TiO2 films deposited by automated nebulizer spray pyrolysis (ANSP) technique at 500 ºC as coating temperature. The manipulation of Ti/Zr ratio on XRD study shows the stabilized anatase tetragonal crystal structure in all deposited films, and the XPS study shows C 1s, Ti 2p, Zr 3d and O 1s are spin orbits of the relative elements. The surface morphological study of FESEM shows the compact granular spherical structure for all the Zr doped TiO2 films. The optical study reveals the blue-shift of band gap energy Eg = 3.20 eV to 3.64 eV with respect to dopant (Zr). Gas sensitivity response of all films exhibits the better response to NH3 reducing gas among the other gas (C2H6O, C3H6O, CH4O, C3H8O) with a function of constant temperature (ºC) and gas concentration (ppm).

Antibacterial performance of glucose-fructose added MW based zirconia coatings – Possible treatment for bone infection

Use of ceramic coatings has increased dramatically in orthopedics by improving their wear resistance and consequent long-term stability. Such stability involves not only the strength of material but also its resistance toward bacterial attacks. Amongst all ceramics, zirconia is selected in the present study due to its white color and high value of hardness making it a potential candidate to be used as implants and their coatings. In the present study effect of varying microwave powers (i.e. 100W, 200W, 300W, 400W, 500W, 600W, 700W, 800W, 900W and 1000W) on sol–gel synthesized glucose and fructose added zirconia coatings has been investigated. Formation of mixed tetragonal – monoclinic phases has been observed at relatively low microwave powers, i.e. 100–500W. However, at 600–1000W phase pure tetragonal zirconia is observed without any post heat treatment. FTIR analysis confirms formation of tetragonal phase of zirconia at 600–1000W microwave power. XPS results confirm the binding energies of Zr 3d and O 1s of microwave assisted zirconia coatings. High value of transmittance, i.e. ~90%, is observed at higher microwave powers. Variation in microwave powers is observed to tune the energy band gap of zirconia coatings in the range of 4.2–5.1 eV. Dielectric constant of 8–10 at log f = 4 is observed. High value of hardness and fracture toughness i.e. 1231 HV and 24.85 MPam−1/2, respectively, is observed for stabilized tetragonal zirconia coatings. Stabilized glucose fructose added zirconia shows strong antioxidant activity. Zirconia coatings are tested against Staphylococcus aureus bacteria for their potential application to treat bone infection. Results suggest that stabilized tetragonal zirconia can be successfully employed for orthopedic coatings.

TiZrN thin films under CO2 and thermal treatment characterized by x-ray photoelectron spectroscopy

TiZrN thin films were prepared by DC magnetron sputtering on silicon (111) substrates. Samples were subjected to different temperature conditions (200, 400, and 600 °C) under a flow of carbon dioxide to emulate a corrosive atmosphere. Each treatment was performed in situ. X-ray photoelectron spectroscopy was used to examine the surface chemical changes on TiZrN thin films before and after the treatments. Survey spectra and C 1s, O 1s, N 1s, Ti 2p, and Zr 3d core level spectra were measured for each sample. Results show remarkable differences in all spectra when the sample was heated over 400 °C. At these temperatures, it is evident that the coating undergoes the greatest chemical change since metals cease to be nitrides and oxidize.

Modifying the Electronic Trap Distribution in Ba2Zr2Si3O12:Eu2+,Nd3+ via Regulating the Composition of Matrix Elements

The appropriate electronic traps and energy gaps between the bottom of the conduction band (CB) and the excited state of the luminescence center are crucial factors for excellent persistent luminescence (PersL) performance. In this article, the possibilities of regulating electronic traps and the energy gap mentioned above are investigated via partial substitution of the host lattice cation Zr4+ by Hf4+. A comprehensive study on the structural transformation, luminescent properties, and PersL decay curves was carried out to unearth the influence of partially substituting Zr4+ ions by Hf4+ ions. The broader band gap was revealed by diffuse reflectance spectra and density functional theory calculations, which ascribed to the relatively higher energy levels of the Hf 5d state compared with those of the Zr 4d state, whereas the thermoluminescence spectra showed a successive red shift because of the broader band gap and the deeper trap depth from the bottom of the CB to the trap energy levels. Guided by regulating the composition of matrix elements through partially substituting Zr4+ ions by Hf4+ ions, the band gap is modified from 5.12 to 5.46 eV and the trap depth varies from 0.66 to 0.75 eV, and the PersL decay time is extended from 25 to 31 h above the recognizable intensity level (≥0.32 mcd/m2).

Phase transformation and modifications in high-k ZrO2 nanocrystalline thin films by low energy Kr5+ ion beam irradiation

In present communication, zirconium oxide (ZrO2) thin films of thickness (155 nm) were grown by using RF sputtering technique. To address and systematically understand the effects of low energy (800 keV) irradiation, high-k ZrO2 thin films were irradiated at room temperature by Kr ions with a range of fluence 1E15 to 1E17 ions. cm−2. The polymorphous zirconia pristine and irradiated thin films were characterized through X-ray diffraction (XRD) technique which confirms the coexistence of monoclinic and tetragonal phases. Monoclinic to tetragonal structural phase transformation was observed for Kr5+ ions irradiated samples at a fluence of 5E15, 1E16, 1E17 ions. cm−2. All samples were characterized by UV–Vis spectroscopy to study the mechanism of variation in optical energy band gap (4.42–4.52 eV), Urbach energy (402–449 meV) and refractive index (1.518–1.523) with increasing ion fluence. Photoluminescence (PL) spectroscopy was done at room temperature to record the significant PL broad prominent emission peaks at 350 nm and 430 nm and the peak intensity of these peaks significantly varies due to the annihilation of primary defects or generation of new defects centres by the influence of Kr ion irradiation. To determine the significant variation in grain size (50–85 nm) and RMS surface roughness (0.54–1.04 nm), pristine and irradiated sample were characterized by atomic force microscopy (AFM). A complete mechanism of the evolution of surface roughness was analyzed by determining the power spectral density (PSD). Further surface roughness component in the range of 0.4–1.7 was calculated using the slope of the tail of PSD. The FTIR spectra of pristine and low energy ion irradiated ZrO2 thin films were recorded in the range of 1250–3200 cm−1. The Rutherford backscattering spectrometry (RBS) was carried out in channeling condition and the experimental results were simulated to evaluate the elemental composition of Zr and O (⁓1:2) and film thickness (155 nm) of the samples. The changes of the chemical binding energy of ZrO2 thin films of Zr 3d and O 1s region before and after ion irradiation were investigated by x-ray photoelectron spectroscopy (XPS).

Zirconium oxide particles, by near-ambient pressure XPS

Near-ambient pressure–x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at ca. 2500 Pa, or even higher in some cases. With NAP-XPS, XPS can probe particles, moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. In this submission, we show survey, narrow (Zr 3p, Zr 3d, and O 1s), and Auger (O KLL) NAP-XPS scans of ZrO2 particles. Charge compensation for this insulating sample took place via the residual gas in the chamber. Zirconia is an important ceramic material. Accordingly, the XPS spectra of zirconia should be useful references.

Intermetallic M Pt3 (M = Ti, Zr, Hf): Elastic, electronic, optical and thermal properties

In this study, the structural and unexplored elastic, electronic, optical and thermal properties of Pt-based alloys MPt3 (M = Ti, Hf) and only optical and thermal properties of ZrPt3 are subjected to investigation using the method of the first principles. The results of pressure dependence of mechanical and thermal properties are discussed. The electronic band structures and density of state data show metallic conductivity for all the compounds. The main contribution at Fermi level comes from Ti 3d and Zr 4d (for TiPt3 and ZrPt[Formula: see text] and Pt 5d (for HfPt[Formula: see text] orbitals. The materials’ optical reflectivity values, relatively high in the IR-visible-UV regions, range from [Formula: see text]62% to 72% in the visible region which show better performance values in comparison to those of some representative materials PtAl2, AuAl2 and GdX3 (X = In, Sn, Tl, Pb). The unexplored thermal behaviors are also investigated via quasi-harmonic Debye model at T = 0 and P = 0 as well as at elevated temperatures and pressures. In addition, when used as bonding materials, studied intermetallics with moderately high thermal expansion coefficients can match other substrates. This coupled with the estimated thermal conductivities (k[Formula: see text]) compared to several other species indicate that the intermetallics can be used in applications, such as thermal barrier coatings (TBC). This study has thus indicated possible alternative candidates for high-temperature applications which would initiate further research and development on the intermetallics under study.

Electronic, Elastic, and Vibrational Properties of ZrBeSi via First Principles

ZrBeSi is the prototype of the ZrBeSi‐type of crystals, but its fundamental properties have not been well studied till now. In this work, a systematic study on the electronic, elastic, and vibrational properties of ZrBeSi under zero and high pressures has been performed by first‐principles calculation. Calculated electronic properties indicate that ZrBeSi is metallic dictated mainly by the Zr 4d state. Its metallicity weakens as the pressure increases. Studies reveal that sp2 hybridization exists in the Be atoms and their 2p orbitals accept electrons from the Zr atoms, leading them to have an unusual negative valency. Calculated elastic properties imply that ZrBeSi is mechanically stable but anisotropic up to 175 GPa. It has a bulk modulus of 144.4 (142.5) GPa deduced from the third‐order Birch–Murnaghan equation of state (elastic constants) at 0 GPa. Its elastic moduli and elastic anisotropy increase with the rising pressure. Group theory analysis unveils that there are six infrared‐active and four Raman‐active modes at the Brillouin zone center of ZrBeSi. The vibrational patterns of these modes are presented and discussed. Studies further reveal that the frequencies of these modes increase with the rising pressure.

Deposition of ZrON thin films by reactive magnetron sputtering using a hollow cylindrical target

ZrON films were prepared on quartz glass and glassy carbon substrates by reactive sputtering using a hollow cylindrical cathode with a Zr target. In the cathode cylinder, the plasma density increased with increasing lateral distance from the axial center of the cylinder, whereas it decreased with increasing lateral distance from the cylinder. The damage to the substrates during film deposition was evaluated by the transmission spectra of Rhodamine B films before and after sputtering. The film deposition was performed in Ar and N2 gas flows with various O2 flow rates while heating the substrates with a ceramic heater. Scanning electron microscope observation indicated homogeneous thickness of the films. X-ray diffraction measurement showed that the ZrON films were a mixture of crystalline ZrN, Zr2ON2, Zr7O8N4, and ZrO2 phases. The fractions of these crystalline phases in the films depended on the O2 flow rate. X-ray photoemission spectroscopy measurement and its analysis revealed that the binding energy of the Zr 3d doublet corresponding to precipitated ZrON crystals in the films, such as Zr2ON2 and Zr7O8N4, increased with increasing oxygen flow rate. Electrochemical measurement revealed that the film deposited at an O2 flow rate of 0.6 sccm had the largest redox potential of 0.51 V (vs standard hydrogen electrode, −5 μA/cm2). The Zr7O8N4 crystals precipitated in the film play a key role in achieving the high redox potential.

Electronic structures and heterogeneity of Zr-Cu-Ag metallic glasses

Photoemission and inverse-photoemission spectroscopy (PES and IPES) measurements were carried out on Zr50Cu50, Zr45Cu45Ag10, and Zr40Cu40Ag20 metallic glasses to investigate the valence- and conduction-band electronic structures, respectively. From the incident photon energy, hν, dependence of the PES spectra, partial DOSs of s and d electrons for the constituent elements were estimated, and it was found that the DOS near EF is mainly composed of Zr 4d electrons and the Cu 3d electrons are localized in the valence band. Core-level PES measurements were also performed at the Zr 3d, Cu 3p, and Ag 3d levels. The Zr 3d core spectra indicate three chemical states in all of these glasses, suggesting a chemical heterogeneity. Energy shifts are observed in the Zr 3d core levels, indicating the charge transfer in the Zr-Cu-Ag metallic glass system.

Nature of the Active Centers of In-, Zr-, and Zn-Aluminosilicates of the ZSM-5 Zeolite Structural Type

In-, Zr-, and Zn- containing elementoaluminosilicates of ZSM-5 zeolite structural type are synthesized by means of hydrothermal crystallization from alkaline alumina–silica gels. Based on the data of structural morphological studies on the samples, it is established that introducting metals into the zeolite structure leads to the formation of particles different in morphology and elemental composition. Studies of the electronic state of active centers in elementoaluminosilicates (E-AS) show that Zn2+ and In3+ cations are associated with oxygen ions in zeolite channels with bonding energies inherent in their oxides. The high value of Zn 3d bonding energy explains the stability of zinc ions in the Zn-AS structure with no formation of clusters under heating the sample by an electron microscope beam. The isomorphic substitution of Al3+ ions in the zeolite crystal lattice by Zr4+ and In3+ ions, despite the relatively low Zr 3d and In 3d bonding energies, also results in the stability of Zr-AS and In-AS systems. It is found that the aggregation of Zr and In into oxide clusters is observed only under strong heating with the electron beam after the destruction of the zeolite channel structure.

Electronic and magnetic properties of AFe2 (A=Zr, Hf, Lu) compounds in the cubic Laves phase

Electronic structures and magnetic properties of three Laves phase iron compounds (ZrFe2, HfFe2 and LuFe2) have been investigated by using full potential linear muffin-tin orbital (FP-LMTO) method within the local spin density approximation LSDA and LDA + U approach. In order to highlight the correlation effect, we have used the LSDA + U approach.The 3d -4d or 3d -5d exchange interactions between Fe and Zr, or Fe and (Hf, Lu) electrons lead to the anti-parallel coupling for Fe (3d) and Zr (4d), or Fe (3d) and (Hf (5d), Lu (5d)) states. In particular this latter approach compared to LSDA method accurately describes the effect of hybridization.The results obtained agree well with other experimental works. We derived the bulk and shear moduli, Young's modulus, and Poisson's ratio. The Debye temperature of ZrFe2, HfFe2 and LuFe2 was estimated from the average sound velocity.

Mechanism of ferroelectric properties of (BaCa)(ZrTi)O3 from first-principles calculations

Electronic, structural, and ferroelectric properties of (BaCa)(ZrTi)O3 (BCZT) were calculated using first-principles calculations and phenomenological Landau-Ginsburg-Devonshire theory. Analysis of relaxed structure and electron charge density shows that the substitution produces different distortion of [TiO6] octahedral at the different site. The double-well potential curve is well fitted by the phenomenological Landau-Ginsburg-Devonshire model. The double-well potential curve is converted to single-well curve with increasing temperature, revealing the ferroelectric-paraelectric phase transition. The spontaneous polarization and well depth of BCZT are reduced in comparison with pure BaTiO3 ferroelectric, which is originated from the squish of Ca ions on the [TiO6] octahedral and the smaller Zr ionic displacement. Analysis of density of states shows that the strong hybridization between Ti 3d and O 2p orbitals and the strong hybridization between Zr 4d and O 2p orbitals are the origin of the ferroelectricity of BCZT materials.

Bonding Structures of ZrHx Thin Films by X-ray Spectroscopy

The variation in local atomic structure and chemical bonding of ZrHx (x=0.15, 0.30, 1.16) magnetron sputtered thin films are investigated by Zr K-edge (1s) X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopies. A chemical shift of the Zr K-edge towards higher energy with increasing hydrogen content is observed due to charge-transfer and an ionic or polar covalent bonding component between the Zr 4d and the H 1s states with increasing valency for Zr. We find an increase in the Zr-Zr bond distance with increasing hydrogen content from 3.160 {\AA} in the hexagonal closest-packed metal (alpha-phase) to 3.395 {\AA} in the understoichiometric delta-ZrHx film (CaF2-type structure) with x=1.16 that largely resembles that of bulk delta-ZrH2. For yet lower hydrogen contents, the structures are mixed alpha and delta-phases, while sufficient hydrogen loading (x>1) yields a pure {\delta}-phase that is understoichiometric, but thermodynamically stable. The change in the hydrogen content and strain is discussed in relation to the corresponding change of bond lengths, hybridizations, and trends in electrical resistivity.

Electronic properties and bonding in ZrHx thin films investigated by valence-band x-ray photoelectron spectroscopy

The electronic structure and chemical bonding in reactively magnetron sputtered ZrHx (x=0.15, 0.30, 1.16) thin films with oxygen content as low as 0.2 at% are investigated by 4d valence band, shallow 4p core-level and 3d core-level X-ray photoelectron spectroscopy. With increasing hydrogen content, we observe significant reduction of the 4d valence states close to the Fermi level as a result of redistribution of intensity towards the H 1s - Zr 4d hybridization region at about 6 eV below the Fermi level. For low hydrogen content (x=0.15, 0.30), the films consist of a superposition of hexagonal closest packed metal (alpha-phase)and understoichiometric delta-ZrHx (CaF2-type structure) phases, while for x=1.16, the film form single phase ZrHx that largely resembles that of stoichiometric delta-ZrH2 phase. We show that the cubic delta-ZrHx phase is metastable as thin film up to x=1.16 while for higher H-contents, the structure is predicted to be tetragonally distorted. For the investigated ZrH1.16 film, we find chemical shifts of 0.68 and 0.51 eV towards higher binding energies for the Zr 4p3/2 and 3d5/2 peak positions, respectively. Compared to the Zr metal binding energies of 27.26 and 178.87 eV, this signifies a charge-transfer from Zr to H atoms. The change in the electronic structure, spectral line shapes, and chemical shifts as function of hydrogen content is discussed in relation to the charge-transfer from Zr to H that affects the conductivity by charge redistribution in the valence band.

Acceptor doping, hydration and band-gap engineering of BaZrO3

Yttrium-doped BaZrO3 powders have been synthesized by sol-gel method. Powder XRD confirms that BaZr1−xYxO3−δ (x = 0.00, 0.05, 0.10) crystallize with the perovskite-type unit cell (space group Pm3‾m). The effects of doping and hydration on the band gap of BaZr1−xYxO3−δ have been evaluated through the analysis of the diffuse reflection spectra. An additional absorption band is observed near the fundamental absorption edge in the doped samples annealed in dry oxygen. These findings are explained by the impact of defects on O(2p)–Zr(4d) charge transfer transitions and by trapping of electrons by oxygen vacancies.

Coke-tolerant SiW20-Al/Zr10 catalyst for glycerol dehydration to acrolein

AbstractGlycerol dehydration to acrolein over a series of supported silicotungstic acid catalysts (SiWx-Al/Zry) was investigated. Characterization results showed that the final catalyst had high thermal stability, a large pore diameter, strong Lewis acidic sites, and a large specific surface area. X-ray photoelectron survey spectra clearly showed peaks attributable to W (W 4f = 35.8 eV), Al2O3 (Al 2p = 74.9 eV), and ZrO2 (Zr 3d = 182.8 eV). The highest acrolein selectivity achieved was 87.3% at 97% glycerol conversion over the SiW20-Al/Zr10 catalyst. The prepared catalysts were highly active and selective for acrolein formation even after 40 h because of the presence of high concentrations of Lewis acidic sites, which significantly reduced the amount of coke on the catalyst surface. Response surface methodology optimization showed that 87.7% acrolein selectivity at 97.0% glycerol conversion could be obtained under the following optimal reaction conditions: 0.5 wt% catalyst, reaction temperature 300 °C, and feed glycerol concentration 10 wt%. Evaluation of a mass-transfer-limited regime showed the absence of internal and external diffusions over pellets of diameter dP < 20 μm. These results show that glycerol dehydration over a strong Lewis acid catalyst is a promising method for acrolein production.

Effects of hydrogen on the nanomechanical properties of a bulk metallic glass during nanoindentation

In this reported work, the effects of hydrogen on the nanomechanical properties of a Zr55Cu30Ni5Al10 bulk metallic glass were investigated. The experimental results demonstrated that the nanohardness of the subject material was significantly reduced as the hydrogen content in glass increased, which was caused by the induced softening from the presence of hydrogen as observed by a decrease in the elastic modulus of the glass. The flow serration of the load-displacement on the glass during nanoindentation gradually became smooth when the hydrogen content was high, which was similar to the nanoindentation loading rate effect. The transition in the flow serration was a distinct physical phenomenon, suggesting a change of in the character of plasticity. A single shear band couldn't accommodate the imposed strain rapidly enough, and consequently multiple shear bands must operate simultaneously. The electronic structure of the hydrogenated Zr55Cu30Ni5Al10 were measured by X-Ray photoemission spectroscopy (XPS). In comparison with their quaternary counterparts, the XPS spectra of the hydrogenated samples were characterized by a shift of the Zr and Al band to lower binding energies. These suggested that the presence of solute hydrogen atoms resulted in the occurrence of the valence electron transferring from the Zr 3d band to the ZrH bonding state, which would weaken the surrounding metallic glass.

Triggering surface ferroelectric order in Pb(Zr,Ti)O3(001) by deposition of platinum

By platinum deposition on a 150nm thick film of lead zirco-titanate oriented PZT(001), grown on strontium titanate (001) single crystals with a strontium ruthenate buffer layer, which did not show initial preferential out-of-plane orientation of its ferroelectric polarization, a band bending near the interface towards lower energies is observed using photoelectron spectroscopy, by following all core levels from the substrate (Pb 4f, Zr 3d, Ti 2p, O 1s). This is unexpected given the fact that platinum has a larger work function than PZT and a rectifying contact for electrons is expected to be built at the interface. This observation may have two explanations: (i) platinum forms an alloy with elements from PZT yielding a metal with considerable lower work function; (ii) platinum provides electrons to the substrate which are able to compensate the depolarization field generated by the outwards polarization state. Several arguments are brought in favor of the second hypothesis, especially the attenuation of core levels from the substrate which is well described by exponential functions with reasonable values of the photoelectron inelastic mean free path, suggesting the formation of a sharp interface. High resolution transmission electron microscopy confirmed the sharpness of the interface.