Solution Of Zr Research Articles

Chemical vapor deposition of Zr xTi 1− xO 2 and Hf xTi 1− xO 2 thin films using the composite anhydrous nitrate precursors

Zr–Ti and Hf–Ti composite nitrates were successfully developed as single-source precursors for the chemical vapor deposition (CVD) of Zr x Ti 1− x O 2 and Hf x Ti 1− x O 2 thin films. The Zr–Ti nitrate can be assumed as a solid solution of the individual Zr and Ti nitrates, and the Zr/Ti molar ratio in the deposited Zr x Ti 1− x O 2 films is consistent with that in the precursor. The Hf–Ti nitrate appears to be a mixture of the Hf and Ti nitrates and the composition of the deposited Hf x Ti 1− x O 2 films depends remarkably on the heating time of precursor. Both Zr x Ti 1− x O 2 and Hf x Ti 1− x O 2 films exhibit trade-off properties between band gap and dielectric constant. The obtained results suggest that Zr x Ti 1− x O 2 and Hf x Ti 1− x O 2 films are promising candidates for gate dielectric application to improve the scalability and reduce the leakage current of the future complementary metal-oxide-semiconductor (CMOS) devices.

Direct synthesis of L10-(Fe, Co)Pt nanocrystallites from (Fe, Co)–Pt–Zr–B liquid phase by melt-spinning

The ordered L10-FePt phase with a size of 20–200nm was directly formed by rapidly quenching the melt in the compositional range of 2–5at.% Zr and 17–20at.% B, and the alloys exhibit coercivity (Hc) higher than 200kA/m in an as-quenched state. In particular, the melt-spun (Fe0.50Pt0.50)78Zr4B18 alloy exhibits high Hc of 684kA/m. The melting temperature (Tm) remarkably decreases by the addition of Zr and B, e.g., from 1837K for FePt to 1345K for (Fe0.55Pt0.45)78Zr4B18. The L10 phase with Zr and B directly formed by the rapidly quenching shows high thermal stability and maintains up to Tm. The simultaneous addition of Zr and B facilitates the direct formation of the ordered L10 phase with a grain size of 20–200nm by rapidly quenching the melt through the effect of the decreasing Tm and the increasing the stability of the L10 phase by the solution of Zr and B into the phase. The substitution of Fe by Co monotonously decreases Tm from 1345K of (Fe0.50Pt0.50)78Zr4B18 to 1083K of (Co0.50Pt0.50)78Zr4B18. However, Hc drastically decreases from 684kA/m of (Fe0.50Pt0.50)78Zr4B18 to 12kA/m of (Co0.50Pt0.50)78Zr4B18, which has a single fcc structure in an as-quenched state. The decrease in Hc with increasing Co content up to Fe:Co=1:3 is caused by the decreasing of the magnetocrystalline anisotropy, which originates from the decreasing the long-range order parameter of the L10 phase.

Residual stress analysis of multi-layered buffer layers on Ni substrate for YBCO coated conductor

CeO 2/YSZ/CeO 2 buffer layer structure is one of the preferred buffer layers for fabrication of coated conductors. Textured CeO 2/YSZ/CeO 2 buffer layers are grown on biaxially textured Ni (100) substrate from the solution of Zr, Y, and Ce based organometalic compounds, solvent and chelating agent using reel-to-reel sol–gel technique. The film thickness is controlled by number of coating withdrawal speed and solution chemistry. Residual stresses arise during the manufacturing process of buffer layers depending on some factors. One of the most important is due to temperature variation. Effects of the temperature variation and coating thickness on residual stress in CeO 2/YSZ/CeO 2 buffer layers structure annealed at high temperature are analyzed theoretically. It is observed that the stress magnitudes reach high levels in the region of interlayer of different materials. The surface morphologies and microstructure of sample are characterized by ESEM and AFM. ESEM and AFM micrographs of the films revealed pinhole-free, crack-free, smooth and dense microstructures in the used manufacturing process.

Low-temperature electrical transport properties of disordered Zr 100−xSn x alloys

The results on the measurement of resistivitiy of solid solutions of Zr 100− x Sn x disordered systems between 1.5 and 300 K are being reported. The study reveals that the transport behaviour is dominated by the weak localization and electron–electron interaction (EEI). The low-temperature resistivity in the absence of a magnetic field obeys T 1/2 law, which is well explained by the EEI. On the basis of the weak localization theory, the electron–phonon scattering time τ e−ph of the Zr 100− x Sn x alloys has been determined from the magnetoconductivity data. The electron–phonon scattering rate τ e - ph - 1 has been observed to be obeying a quadratic temperature dependence. This observation owes its explanation to the existing theory of electron–phonon interaction.

Synthesis of (Ba,Ca)(Zr,Ti)O<sub>3</sub> Ceramics from Ultra-Fine Precursors

Fine powder of CaZrO3 (CZ) was synthesized by using ultra-fine and highly dispersed CaCO3 as a precursor. The results showed that the calcination temperature could be reduced to inhibit grain growth of CZ. Mean grain size of the CZ fine powder was 80 nm. Moreover, the CZ powder was used to synthesize a solid solution of (Ba,Ca)(Zr,Ti)O3 (BCZT) to examine the effect of the powder’s grain size on the reactivity of BT and CZ. It was found that the fine CZ powder enhanced the BT and CZ reaction.

Chemical Vapor Deposition of ZrxTi1-xO and HfxTi1-xO Thin Films Using the Composite Anhydrous Nitrate Precursors

AbstractZr/Ti an Hf/Ti composite nitrate were developed as single-source precursors for deposition of multi-component metal oxide films. X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) analyses confirmed that ZrxTi1-xO2 and HfxTi1-xO2 films were successfully prepared by the CVD technique from these composite precursors. The Zr/Ti nitrate can be taken as a solid solution of the individual Zr and Ti nitrate, and the Zr/Ti molar ratio in as-deposited ZrxTi1-xO2 films is nicely consistent with that of the precursor. The Hf/Ti nitrate appears to be a mixture of the Zr and Ti nitrates and the composition of the as-deposited HfxTi1-xO2 films depends remarkably on the heating time of precursor. Both ZrxTi1-xO2 and HfxTi1-xO2 films exhibit trading-off properties between band gap and dielectric constant, which suggesting that ZrxTi1-xO2 and HfxTi1-xO2 can be the promising candidates for gate dielectric application to improve the scalability and reduce the leakage current of the next generation complementary metal-oxide-semiconductor transistor (CMOS) devices.

Synthesis and crystal structure of [C 6N 2H 14]⋅(Zr 2F 10)⋅1.5H 2O A new one-dimensional zirconium fluoride templated with DABCO

A new organic–inorganic zirconium (IV) fluoride, [C 6N 2H 14]⋅(Zr 2F 10)⋅1.5H 2O, is prepared by slow evaporation at 45 °C from a solution of Zr 4+ and of 1,4-diazabicyclo[2.2.2]-octane (DABCO) in 40% aqueous HF. The structure, determined from single-crystal X-ray diffraction, is monoclinic, space group C 2 / m , a = 19.598 ( 8 ) Å , b = 6.658 ( 3 ) Å , c = 10.891 ( 3 ) Å , β = 101.25 ( 4 ) ° and Z = 4 . Previously unknown ∞(Zr 2F 10) 2− double chains, built up from edge-sharing ZrF 7 pentagonal bipyramids and ZrF 8 trigonal dodecahedra, are observed. The diprotonated organic cations, water molecules and the ∞(Zr 2F 10) 2− chains are linked by hydrogen bonds.

New Preparation Methods for Composite Membranes for Medium Temperature Fuel Cells Based on Precursor Solutions of Insoluble Inorganic Compounds

AbstractCurrent PEMFCs, using perfluorinated membranes, can only operate at temperatures no higher than 70–80 °C, since their performance is dramatically reduced at higher temperatures. Encouraging results, for avoiding the reduction in performance, can be obtained by filling Nafion® membranes with inorganic nano‐particles (composite membranes) and/or by adding inorganic nano‐particles at the membrane/electrode interfaces. However, the efficient insertion of nano‐particles, other than metal oxides, inside a polymeric matrix is often very complicated or not possible. Therefore, it was of interest to find simpler methods for the insertion. In this paper, the preparation of organic precursor solutions of the insoluble compound Zr(O3P‐OH)(O3P‐C6H4SO3H), a proton conductor exhibiting very high conductivity (10–1 S cm–1 at 100 °C and 90 %RH) is reported. It was found that these precursor solutions are more stable the higher the Kb of the solvent and the lower the temperature. Precursor solutions, stable for many days at room temperature, were found by using proton acceptor solvents, such as alkanols, N,N‐dimethyl formamide (DMF), and N‐methyl pyrrolidone (NMP). The particularity of these solutions is that insoluble phosphonate particles are formed when the solvent is evaporated. They are therefore very suitable for filling porous membranes, for the preparation of composite proton conducting membranes, and for the preparation of composite electrodes. Some examples of preparation and use are reported and discussed.

Thermal stability and surface acidity of mesoporous silica doubly doped by incorporation of sulfate and zirconium ions

A sulfated Si–Zr–MCM-41 solid with highly ordered mesostructure was synthesized through a templated synthesis route where the CTAB surfactant was used as template. During the synthesis procedure, various amounts of (NH 4) 2SO 4 were added into the mixed solution of Zr and Si precursors to in situ sulfate the MCM-41 solids, aiming to enhance the acidity and thermal stability. The resultant materials showed a long-range ordered hexagonal arrangement with high surface area larger than 797 m 2/g and an average pore size distributed at approximate 2.5–2.8 nm. The high-resolution TEM observations confirmed that the order of the mesostructure gained when the molar ratio of SO 4 2−/(ZrO 2 + SiO 2) increased from 0.1 to 0.3 but decreased as it reached 0.5, which is consistent with the results of 29Si MAS–NMR and XRD analysis. Compared to Si–MCM-41, the (Q 2 + Q 3)/Q 4 ratio derived from the NMR spectra of the Zr-doped sample was higher, indicating that zirconium atoms were incorporated into the silica framework. Unexpectedly, in situ sulfation does not enhance the surface Brönsted acidity, most likely due to the sulfur retained within the bulk of the materials; however, it indeed improved the thermal stability of the solid and long-range order of the structure.

Thermodynamic properties of trizirconium tetraphosphate

The heat capacity measurements of the crystalline trizirconium tetraphosphate were carried out in a low-temperature adiabatic vacuum calorimeter between T = (7 and 350) K and in dynamic calorimeter between T = (330 and 640) K. The experimental data were used to calculate the standard ( p ∘ = 0.1 MPa) thermodynamic functions C p , m ∘ / R , Δ 0 T H m ∘ / RT , Δ 0 T S m ∘ / R , and Φ m ∘ = Δ 0 T S m ∘ - Δ 0 T H m ∘ / T (where R is the universal gas constant) in the range T → (0 to 640) K. The fractal dimension D fr for the crystalline phosphate Zr 3(PO 4) 4 between T = (20 and 40) K was evaluated. From hydrofluoric acid solution microcalorimetry, the enthalpy of solution of Zr 3(PO 4) 4 at T = 298.15 K was determined and the standard molar enthalpy of formation was derived. By combining the data obtained by the two techniques, the standard molar Gibbs function of formation of Zr 3(PO 4) 4 at T = 298.15 K was calculated.

PZT prepared by spray drying: From powder synthesis to electromechanical properties

A PZT niobium-doped material (PZTN) was developed from precursor powders obtained by spray drying of water solution of Zr and Pb nitrates, Ti isopropoxide and Nb–ammonium complex. The thermo-oxidative process as well as the phase evolution were analysed. The morphology of powders was investigated as a function of the spray-drying conditions. The stoichiometry of the systems was checked at each stage of the process and no fluctuation was detected. The obtained powders had a spherical, hollow and porous structure and were transformed into a pure perovskite phase at 550 °C. The samples, sintered at 1100 °C for 2 h in air showed 98% relative density at densification temperature of 100 °C lower than following the conventional mixed oxide route. The green and final densities were improved by introducing a grinding step and high pressure cold isostatic consolidation. Some sintered samples were fully densified by hot isostatic pressing (1100 °C, 300 bars) post-treatment, obtaining pore free structures. The electrical characterisation showed comparable or better properties than those obtained with the mixed oxide method.

Comparative study of benzylation of benzene using benzyl chloride in the presence of pillared bentonite; ion-exchanged and pillaring solution impregnated montmorillonite K10

Montmorillonite K10 was modified with pillaring solutions of Fe, Al and Zr (K10-MPLS). The catalysts were activated at 120 and 550 °C. The resultant catalysts were used for the Friedel–Crafts benzylation of benzene with benzyl chloride under mild experimental conditions. Amongst them, K10-FePLS120 catalyst showed both high activity and selectivity for the benzylation reaction at room temperature (28 °C). The catalyst can also be reused in the benzylation for several times. The activities of these catalysts were compared with those of Fe3+-, Al3+- and Zr4+-exchanged montmorillonite K10 and Fe-, Al- and Zr-pillared bentonite catalysts. The benzylation of various monosubstituted benzenes was carried out using K10-FePLS120.

Electrodeposition of Al-Zr Alloys from Lewis Acidic Aluminum Chloride-1-Ethyl-3-methylimidazolium Chloride Melt

The electrochemistry of Zr(IV) and Zr(II) and the electrodeposition of Al-Zr alloys were examined in the Lewis acidic 66.7-33.3 mol % aluminum chloride-1-ethyl-3-methylimidazolium chloride molten salt at 353 K. The electrochemical reduction of Zr(IV) to Zr(II) is complicated by the precipitation of however, solutions of Zr(II) can be prepared by reducing Zr(IV) with Al wire. Al-Zr alloys can be electrodeposited from plating baths containing either Zr(IV) or Zr(II), but for a given concentration and current density, baths containing Zr(IV) lead to Al-Zr alloys with the higher Zr content. This result was traced to the diminutive concentration-dependent diffusion coefficient for Zr(II). It was possible to prepare Al-Zr alloys containing up to ∼17% atomic fraction (atom %) Zr. The structure of these deposits depended on the Zr content. Alloys containing less than 5 atom % Zr could be indexed to a disordered face-centered cubic structure similar to pure Al, whereas alloys containing ∼17 atom % Zr were completely amorphous (metallic glass). The chloride pitting potentials of alloys with more than 8 atom % Zr were approximately +0.3 V relative to pure Al. © 2004 The Electrochemical Society. All rights reserved.

99mTc gel generators based on zirconium molybdate-99Mo: III: Influence of preparatory conditions of zirconium molybdate-99Mo gel on generator performance

AbstractThe effect of subtle variations on zirconium molybdate-99Mo gel preparatory conditions, such as stoichiometry of reactants, pH of gel formation, conditioning of gel granulesetc., prior to elution were investigated primarily to arrive at the conditions resulting in high99mTc release and minimal99Mo breakthrough upon elution with normal saline. Zirconium molybdate-99Mo gels were prepared by reacting solutions of Zr and Mo in mole ratios of 0.75-1.5. Both water and normal saline were used for gel disintegration, and the release of99mTc and99Mo from gel columns into eluates was compared. Sharper elution profile of99mTc, but with significantly higher99Mo breakthrough (5-8 times), was obtained when water alone was used for disintegration and elution, in comparison to when saline was used.Gels exhibiting optimum characteristics were found to be formed at a pH of 4-5 by reacting [Zr]:[Mo] in the mole ratio of 1.25:1 and after drying, the product was dispersed into granules by disintegration with normal saline.99mTc elution efficiency was found to be ∼75% and99Mo breakthrough ∼0.05%. The elution profile was sharp when a 6 g gel column coupled to a 2 g acidic alumina column (to trap99Mo) was eluted with 6-9 ml normal saline. Generators containing upto 23 GBq99Mo were prepared, eluted extensively without changing the alumina column and found to provide pertechnetate of good quality, commensurate with hospital radiopharmacy requirements.

Direct Synthesis of <i>L</i>1<SUB>0</SUB> (Fe<SUB>0.55</SUB>Pt<SUB>0.45</SUB>)<SUB>77—78</SUB>Zr<SUB>2—5</SUB>B<SUB>17—20</SUB> Nanocrystalline Alloys with High Coercivity by Melt-Spinning

The structure and the coercivity (Hc) of the rapidly quenched (Fe0:55Pt0:45)bal.Zr0{8B0{24 alloys prepared by the melt-spinning technique have been investigated. The ordered L10-FePt phase with a size of 20–200 nm was directly formed by rapidly quenching the melt in the compositional range of 2–5 at% Zr and 17–20 at% B, and the alloys exhibit Hc greater than 200 kA/m in an as-quenched state. In particular, the melt-spun (Fe0:55Pt0:45)78Zr2B20 and (Fe0:55Pt0:45)78Zr4B18 alloys exhibit high Hc of 341 kA/m and 649 kA/m, respectively. The melting temperature (Tm) remarkably decreases by the addition of Zr and B, e.g., from 1833 K for Fe55Pt45 to 1360 K for (Fe0:55Pt0:45)78Zr4B18. The L10 phase, which is directly formed by the rapidly quenching method, is considered to include Zr and B, shows high thermal stability and maintains up to Tm. On the other hand, the (Fe0:55Pt0:45)77{85Zr0{8B15{22 alloys, produced by the Cu-mold casting with a lower cooling rate than the meltspinning technique are found to comprise of mixed structures of L10-FePt and some compound phases such as ZrB12, PtZr, Fe3B, and FeB, and the alloys have a Hc of 40–100 kA/m, which is lower than that of the melt-spun alloys. Apart from the L10 phase, the other phases such as ZrB12, PtZr, Fe3B, and FeB are suppressed and the L10 phase containing Zr and B elements is formed by rapidly quenching the alloy melt with low Tm. The simultaneous addition of Zr and B facilitates the direct formation of the ordered L10 phase with a grain size of 20–200 nm by rapidly quenching the melt through the effect of the decreasing Tm and the increasing the stability of the L10 phase by the solution of Zr and B into the phase.

Solution deposition of ultrathin zirconia films on YBa2Cu3O7−δby molecular layering of tetra-n-propyl zirconate

Ultrathin (<10 nm) zirconia films were deposited on (001) and (103) YBa2Cu3O7−δ (YBCO) films by alternating exposure of the YBCO film surfaces to methylcyclohexane solutions of ultrapure Zr(OPrn)4 and n-propanol solutions of H2O. The electrical properties of silver/zirconia/YBCO sandwiches derived from such bilayers were studied using planar tunneling spectroscopy. These studies showed that ultrathin zirconia films can serve as viable tunnel barriers below the YBCO superconducting phase transition temperature. According to atomic force microscopy and transmission electron microscopy, the zirconia films were remarkably conformal, uniform, and pinhole-free.

Thin-film shape-memory materials for high-temperature applications

Many applications of shape-memory alloys (SMAs) are likely to require development of alloys having much higher martensite transformation temperatures than are currently available. This article reviews recent reports on a few promising systems, with emphasis on sputtered films in the NiTiX group. NiTiX is a name for the ternary ordered substitutional solutions of Hf, Zr, Au, Pd, or Pt, in the β-NiTi lattice. These have been the most extensively studied compounds and the only high-temperature SMAs yet fabricated as thin films. For films, the exaggerated kinetics of physical vapor deposition and the generous surfaces of the planar form confer economic and technical advantages, especially in cases involving costly additions or troublesome solidification issues. The outlook for technically useful SMAs operating at up to 240°C is quite good. Operation at temperatures above 500°C may be possible, but issues of thermal stability will pose significant challenges.

Microstructural characterisation and thermal stability of a metastable Mg-8.6 wt.% Zr alloy produced by physical vapour deposition

Abstract The thermal stability of a Mg-8.6 wt.% Zr alloy processed by physical vapour deposition has been studied using differential scanning calorimetry and transmission electron microscopy. The alloy, in the as-deposited condition, is a solid solution of Zr in the Mg matrix. The microstructure is characterised by elongated grains oriented with their [0001] direction parallel to the growth direction. After DSC experiments, three exothermic transformations have been observed. The first one takes place above the deposition temperature and is related to the recovery phenomena due to stress relaxation generated during the growth process. The second transformation corresponds to the breakdown of the solid solution by the precipitation of Zr in the Mg matrix. This reaction takes place in two stages: (i) Zr plates are formed in the basal plane and (ii) these initial precipitates grow along the [0001] direction. An epitaxial relationship between those Zr precipitates and the Mg matrix of [0001]Zr || [0001]Mg and...

Insulation coating of silver tapes using an organometallic solution of Zr and Ca for application to Bi-based superconductors

Silver tapes were spray coated using an organometallic solution as the carrier liquid. When this solution was annealed in air at 825 °C, ∼4% of its total weight remained as CaZrO3. Mixtures of Bi2O3, SrCO3 and CaCO3 have been prepared with seven different stoichiometries. An organometallic solution was mixed with ceramic oxide powders and spray coated onto silver tapes. Electrical insulation tests were performed applying a dc potential, and insulation survived more than 30 V. Coated tapes were coiled to progressively decreasing diameters down to 1 mm diameter with no sign of cracking, indicating the possibility of metallic bonding and diffusion. This technique appears to be suitable for use in the insulation of Bi-based superconducting tapes and wires, since it does not contain any element that is chemically reactive to this system.

Direct Formation of Zirconia‐Doped Titania with Stable Anatase‐Type Structure by Thermal Hydrolysis

Nanoparticles of anatase‐type titania (TiO2) doped with zirconia (ZrO2) were directly synthesized from acidic precursor solutions of TiOSO4 and Zr(SO4)2 by simultaneous hydrolysis, under mild hydrothermal conditions, at 200° and 240°C. Doping ZrO2 into TiO2 suppressed the crystal growth of anatase and shifted the phase transformation from anatase‐type to rutile‐type structure to a high temperature. The presence of an anatase‐type structure with high crystallinity and high phase stability, even after annealing at 1000°C for 1 h, was fully achieved by both the doping of ZrO2 into TiO2 through direct precipitation and the simultaneous hydrolysis of the sulfate solutions.