Tetragonal Zr Research Articles

Influence of the Surface Chemical Composition Differences between Zirconia and Titanium with the Similar Surface Structure and Roughness on Bone Formation.

The osseointegration of zirconia (ZrO2) implants is still controversial. In this study, we aimed to make clear the influence of surface chemical composition, Ti or ZrO2, to osseointegration. First, a roughened Ti surface was prepared with a combination of large-grit sandblasting and acid treatment. Then, we applied molecular precursor solution containing Zr complex onto roughened Ti surface and can deposit thin ZrO2 film onto roughened Ti surface. We can change surface chemical composition from Ti to ZrO2 without changing the surface structure and roughness of roughened Ti. The tetragonal Zr was uniformly present on the ZrO2-coated Ti surface, and the surface of the ZrO2-coated Ti showed a higher apparent zeta potential than Ti. Ti and ZrO2-coated Ti rectangular plate implant was placed into the femur bone defect. After 2 and 4 weeks of implantation, histomorphometric observation revealed that the bone-to-implant contact ratio and the bone mass values for ZrO2-coated Ti implants inserted into the femur bone defects of the rats at 2 weeks were significantly higher than those for Ti implants (p < 0.05). It revealed that ZrO2 with a similar surface structure and roughness as that of roughened Ti promoted osteogenesis equivalent to or better than that of Ti in the early bone formation stage.

Contributions to the stereochemistry of zirconium oxysalts\u2014part IV: syntheses and crystal structures of Zr2(OH)2(XO4)3\xb74H2O (X\u2009=\u2009S, Se), Zr(SO4)2\xb74H2O, and Zr(SeO3)2

Zr2(OH)2(XO4)3·4H2O (X = S, Se), Zr(SO4)2·4H2O, and Zr(SeO3)2 were synthesized at low-hydrothermal conditions from mixtures of Zr2O2(CO3)(OH)2, the respective acids, and minor amounts of water. While Zr2(OH)2(XO4)3·4H2O (X = S, Se) and Zr(SO4)2·4H2O form crystals up to several tenths of a mm, Zr(SeO3)2 was mainly obtained as microcrystalline powder, single crystals rarely exceeded 10 μm in size. Samples were investigated by single-crystal X-ray techniques and in the case of Zr(SeO3)2 also by X-ray powder diffraction. The compounds Zr2(OH)2(XO4)3·4H2O (X = S, Se) crystallize in the Ce2(OH)2(SO4)3·4H2O structure type (C2/c, Z = 4, a = 13.034(2) / 13.308(3), b = 6.500(1) / 6.683(2), c = 15.056(3) / 15.383(4) Å, β = 96.27(1) / 96.81(1)°, V = 1267.9(4) / 1358.5(6) Å3 for X = S / Se, respectively). Tetragonal aniprisms Zr[8]O8 are edge-connected to dimers that share corners with XO4 tetrahedra forming a three-dimensional network. Zr(SO4)2·4H2O (Fddd, Z = 8, a = 5.498(1), b = 11.618(3), c = 25.893(6) Å, V = 1653.9(6) Å3) is isotypic with the respective selenate compound. Occasionally, pseudomerohedral twinning is observed, simulating a larger monoclinic C-centered unit cell. Again, tetragonal antiprisms Zr[8]O8 are formed; however, they are corner-linked with SO4 tetrahedra to Zr(SO4)2 layers interconnected solely by hydrogen bonds. Zr(SeO3)2 crystallizes in P21/c, Z = 2; a = 4.9724(3), b = 8.5992(5), c = 6.9447(3) Å, β = 110.128(3)°, V = 278.81(3) Å3 (unit cell from powder data) and belongs to the β-Sn(SeO3)2 structure type established further for Ti(SeO3)2 and Pb(SeO3)2. Isolated ZrO6 octahedra share corners with the selenite groups forming a three-dimensional network.Graphical abstract

Dose distrubution evaluation of different dental implants on a real human dry-skull model for head and neck cancer radiotherapy

ObjectivesIn this study, the effect of different dental implant materials on dose distribution in head and neck cancer radiotherapy planning was investigated in a real human dry-skull taken from cadaver. MethodsThe effect of Root-shaped Yttrium (Y) stabilized tetragonal Zr polycrystalline (Y-TZP), Titanium (Ti), Alumina (Al2O3) and polyether ether ketone (PEEK) dental implants on dose distribution was investigated by three different methods; Monte Carlo (MC) simulation, Eclipse Treatment Planning System's (TPS) Pencil Beam Convolution (PBC) algorithm and Thermoluminescence Dosimeter (TLD). The 6 MV photon beam simulation was performed for the Varian 2300 C/D linear accelerator using the EGSnrc based BEAMnrc MC Code. To perform MC simulation on skull phantom, phantom CT images with extended CT scale were imported to BEAMnrc/EGSnrc MC code via CTCREATE code. ResultsAccording to the dose distribution measurement in dry skull, the calculated dose differences between PBC and MC algorithms were in the range of 0.6–4.5% whereas the dose difference between MC and TLD were in the range of 1,1–14.6% range depending on implant material. The PBC calculated dose increase difference range confirmed with TLD measurements was between 1.7% and 19.8%. The PBC algorithm could not fully determine the dose due to backscattering caused by dental implants. This is probably due to the limitations and shortcomings of the PBC algorithm. ConclusionThe maximum dose increase was observed for the Y-TZP dental implant material, which has the highest physical density. No significant dose increase was observed for the PEEK implant probably due to the low physical density of implants close to the physical density of water.

In-plane orientation and composition dependences of crystal structure and electrical properties of {100}-oriented Pb(Zr,Ti)O3 films grown on (100) Si substrates by metal organic chemical vapor deposition

In-plane orientation-controlled Pb(Zrx,Ti1−x)O3 (PZT) films with a thickness of approximately 2 µm and a Zr/(Zr + Ti) ratio of 0.39–0.65 were grown on (100) Si substrates by pulsed metal–organic chemical vapor deposition (MOCVD). In-plane-oriented epitaxial PZT films and in-plane random fiber-textured PZT films with {100} out-of-plane orientation were grown on (100)c SrRuO3//(100)c LaNiO3//(100) CeO2//(100) YSZ//(100) Si and (100)c SrRuO3/(100)c LaNiO3/(111) Pt/TiO2/SiO2/(100) Si substrates, respectively. The effects of Zr/(Zr + Ti) ratio and in-plane orientation on the crystal structure, dielectric, ferroelectric, and piezoelectric properties of the films were systematically investigated. The X-ray diffraction measurement showed that the epitaxial PZT films had a higher volume fraction of (100) orientation than the fiber-textured PZT films in the tetragonal Zr/(Zr + Ti) ratio region. A large difference was not detected between the epitaxial films and the fiber-textured films for Zr/(Zr + Ti) ratio dependence of the dielectric constant, and remanent polarization. However, in the rhombohedral phase region [Zr/(Zr + Ti) = 0.65], coercive field was found to be 1.5-fold different between the epitaxial and fiber-textured PZT films. The maximum field-induced strains measured at 0–100 kV/cm by scanning atomic force microscopy were obtained at approximately Zr/(Zr + Ti) = 0.50 and were about 0.5 and 0.3% for the epitaxial and fiber-textured PZT films, respectively.

Influence of second phase particles on corrosion resistance of N36 alloy in superheated steam

The nodular corrosion resistance of N36 (Zr–0.8Sn–1Nb–0.3Fe–0.12O, wt%) alloy with different temperatures of interstage annealing and optimized Zircaloy-4 (lower content of tin) cladding tubes were tested in 500 °C and 10.3 MPa superheated steam. The result showed that no nodular spots appeared on surface of N36 alloy cladding tubes after 500 h corrosion, while nodular spots on optimized Zircaloy-4 tubes after 8 h. The differences of weight gain between two kinds of N36 tubes suggested that the percentage (volume fraction) of tetragonal Zr dioxide in oxide film can be effectively influenced by characteristics, such as size, of the second phase particles on the oxide film-matrix boundary. The analysis by SEM and LRS clearly indicated that smaller and fine distributed second phase particles were beneficial to stabilize the oxide via endure the uniform stress so it could slow down the altering process from tetragonal Zr dioxide to monoclinic Zr dioxide.

Precipitation behaviors of cubic and tetragonal Zr–rich phase in Al–(Si–)Zr alloys

The precipitation behaviors of Zr–rich phase in binary Al–0.5Zr and ternary Al–3Si–0.5Zr alloys were investigated by high resolution transmission electron microscopy and atom probe. After the alloys were aged at 525 °C for 24 h, the precipitates in Al–0.5Zr alloy are identified as L12–ZrAl3, performing a coherent relationship with the Al matrix. While in Al–3Si–0.5Zr alloy, the precipitates are Si–containing D023–Zr(Al,Si)3, which has an approximate 90° reversed cube–on–cube orientation relationship with Al. It is regarded that Si accelerates the precipitation of D023–Zr(Al,Si)3.

Microstructure evolution of ZrO2–YbTaO4 thermal barrier coatings

The ZrO2–YbO1.5–TaO2.5 system offers significant promise in the development of next generation thermal barrier coatings (TBCs) but there is a paucity of information on its processability by established technology and its subsequent evolution upon aging. This investigation provides insights on the as-deposited microstructure of a ZrO2–20YbO1.5–20TaO2.5 (mol.%) TBC produced by electron-beam physical vapor deposition (EB-PVD), and its evolution during aging at 1250–1700°C. Complementary studies were performed on precursor-derived materials of the same composition, as well as on a chemically similar ZrO2–20YO1.5–20TaO2.5 EB-PVD TBC. The coatings are deposited as a tetragonal single phase supersaturated (and hence metastable) solid solution which decomposes upon aging at 1250°C into a uniform dispersion of coherent nano-scale tetragonal YbTa(Zr)O4 precipitates within the depleted tetragonal Zr(Yb, Ta)O2 matrix. Similar microstructures were produced from precursor-derived materials when aged above the tantalate solvus, identified as ∼1450°C. Aging of similar samples below the solvus leads to much coarser YbTa(Zr)O4 second phase, with monoclinic tantalate emerging below 1350°C and the tetragonal form appearing between 1350°C and 1450°C. The remarkable phase stability of the TBC after aging is attributed to the fine scale dispersion of the second phase.

Synthesis, phase transition and negative thermal expansion of cubic Zr(W1−yMoy)2−xVxO8−x/2 (y = 0.10, 0.20, 0.30, 0.40; 0 ⩽ x ⩽ 0.40) solid solutions

We first prepared tetragonal Zr(W1−yMoy)2−xVxO7−x/2(OH)2⋅2H2O (y=0.10, 0.20, 0.30, 0.40; 0⩽x⩽0.40) hydrate precursors through acidic steam hydrothermal (ASH) treatment. Dehydration of these precursors produces the corresponding low temperature orthorhombic polymorph Zr(W1−yMoy)2−xVxO8−x/2. Upon annealing at 813–873K for 2h this intermediate further transforms to the end product of kinetically favored cubic Zr(W1−yMoy)2−xVxO8−x/2 solid solutions. The dehydration and orthorhombic to cubic phase transition temperatures decrease linearly with increasing Mo and constant V content; the orthorhombic to cubic phase transition temperature also decreases linearly with increasing V content at constant W/Mo ratio. Measurements of thermal stability and expansion indicate that cubic Zr(W1−yMoy)2−xVxO8−x/2 solid solutions have strong negative thermal expansion property. We characterized the average structure of c-Zr(W0.90Mo0.10)1.76V0.24O7.88 using Rietveld refinement method, calculated lattice parameters of solid solutions and solid solubility at different y value, and discuss structural factors that affect cell parameter values.

Tailoring the magnetism of Tb5Si2Ge2compounds by La substitution

In order to study the crystal structure, phase relationships, and magnetic properties of the system Tb${}_{5\ensuremath{-}\mathit{x}}$La${}_{\mathit{x}}$Si${}_{2}$Ge${}_{2}$, a series of polycrystalline samples with compositions ranging from $x=0$ to $x=5$ have been synthesized and characterized in detail. At room temperature, two structures have been detected: Compounds in the concentration range $0\ensuremath{\leqslant}x&lt;1$ present a monoclinic Gd${}_{5}$Si${}_{2}$Ge${}_{2}$-type structure, while for $x&gt;1$ a tetragonal Zr${}_{5}$Si${}_{4}$-type structure is observed. The unit cell volume increases linearly with La concentration but with two different slopes: $\ensuremath{\sim}$18 \AA{}${}^{3}/x$ and $\ensuremath{\sim}$33 \AA{}${}^{3}/x$ for $0\ensuremath{\leqslant}x&lt;1$ (monoclinic) and $x&gt;1$ (tetragonal), respectively. In the monoclinic region, an increase of ${T}_{C}$ was observed, reaching a maximum value of ${T}_{C}$ $\ensuremath{\sim}154$ K, at the $x=0.75$ composition. This feature is explained based on specific La occupancy at the $R2$ site which was supported by density functional calculations for low La concentration. The samples that crystallized in the tetragonal structure exhibit a linear decrease of ${T}_{C}(x)$ with a slope of $\ensuremath{\partial}{T}_{C}$/$\ensuremath{\partial}x$ $\ensuremath{\sim}\ensuremath{-}38$ K/$x$, reaching 0 K for the $x=5$ composition. A magnetic and structural $x$-$T$ phase diagram of the Tb${}_{5\ensuremath{-}\mathit{x}}$La${}_{\mathit{x}}$Si${}_{2}$Ge${}_{2}$ system in the temperature range 4--300 K is proposed.

Effects of annealing on Zr 8Ni 19X2 ( X = Ni, Mg, Al, Sc, V, Mn, Co, Sn, La, and Hf): Structural characteristics

The effects of an 8-h annealing treatment at 960 °C on the phase structures of a series of partial-Ni substituted Zr 8Ni 21 alloys, potential metal hydride candidates for high-rate nickel/metal hydride batteries, were studied. The substitution elements included Mg, Al, Sc, V, Mn, Co, Sn, La, and Hf. Only the main phase of the annealed Sn-substitution remained Zr 8Ni 21-structured while those of other substitutions turned into Zr 7Ni 10 or Zr 2Ni 7. Similar to the preference of C14/C15 main phase in AB 2 alloys, the number of outer-shell electrons played an important role in determining the main phase of the A 8B 21 alloys. As the number of outer-shell electrons of the substituting element increased, the main phase evolved from tetragonal Zr 7Ni 10 (Mg, Al, and Sc), to orthorhombic Zr 7Ni 10 (La and Hf), cubic Zr 2Ni 7 (V, Mn, Co, and Sn (before annealing)), and finally triclinic Zr 8Ni 21 (Ni and Sn (after annealing)). After annealing, the abundance of the predominant phase increased, and the number of secondary phases diminished. The only exception was the Sn-substituted alloy, where the major phase transformed from Zr 2Ni 7 to Zr 8Ni 21 (after annealing). In this study, several alloys showed an X-ray diffraction peak at around 38.4°, which cannot be correlated to any phase in the database. The stoichiometry of this phase is close to Zr 2Ni 7 according to X-ray energy dispersive spectroscopy.

Chemical Pressure and Rare-Earth Orbital Contributions in Mixed Rare-Earth Silicides La5–xYxSi4 (0 ≤ x ≤ 5)

A crystallographic study and theoretical analysis of the structural and La/Y site preferences in the La(5-x)Y(x)Si(4) (0 ≤ x ≤ 5) series prepared by high-temperature methods is presented. At room temperature, La-rich La(5-x)Y(x)Si(4) phases with x ≤ 3.0 exhibit the tetragonal Zr(5)Si(4)-type structure (space group P4(1)2(1)2, Z = 4, Pearson symbol tP36), which contains only Si-Si dimers. On the other hand, Y-rich phases with x = 4.0 and 4.5 adopt the orthorhombic Gd(5)Si(4)-type structure (space group Pnma, Z = 4, Pearson symbol oP36), also with Si-Si dimers, whereas Y(5)Si(4) forms the monoclinic Gd(5)Si(2)Ge(2) structure (space group P2(1)/c, Z = 4, Pearson symbol mP36), which exhibits 50% "broken" Si-Si dimers. Local and long-range structural relationships among the tetragonal, orthorhombic, and monoclinic structures are discussed. Refinements from single crystal X-ray diffraction studies of the three independent sites for La or Y atoms in the asymmetric unit reveal partial mixing of these elements, with clearly different preferences for these two elements. First-principles electronic structure calculations, used to investigate the La/Y site preferences and structural trends in the La(5-x)Y(x)Si(4) series, indicate that long- and short-range structural features are controlled largely by atomic sizes. La 5d and Y 4d orbitals, however, generate distinct, yet subtle effects on the electronic density of states curves, and influence characteristics of Si-Si bonding in these phases.

An in situ neutron diffraction study of the thermal disproportionation of the Zr 2FeD 5 system

The Zr 2FeD 5 system has been annealed to 680 °C under ultra high vacuum, and studied in situ by neutron diffraction. The system disproportionates through three distinct regions in temperature. Initially, the tetragonal Zr 2FeD 5 ( P4/ ncc) is retained up to 330 °C, while steadily depleted of D. From 330 °C to 530 °C, a complex multi-phase disproportionation occurs, with the production of cubic ZrD 2, tetragonal ZrD 2, tetragonal Zr 2FeD 5 ( I4/ mcm), and growth of the intermetallic ZrFe 2. At the beginning of the 330–530 °C period, the total atom count from quantitative phase analysis (QPA) indicates the formation of amorphous (a-) Zr 56Fe 44. By 530 °C, QPA and peak breadth analysis indicate that ca. 2/3rd of the sample is consumed as very small nanocrystals (<150 Å coherence length) of strained ZrD 2. From 530 °C to 680 °C, the cubic ZrD 2 is almost entirely consumed and depleted of D to form the final mixture of the intermetallic phases Zr 3Fe and ZrFe 2. QPA of the final intermetallic mixture yields a Zr:Fe ratio greater than that observed in either the arc melted alloy or the initial Zr 2FeD 5 deuteride, indicating that a ca. Zr 71Fe 29 amorphous component was present in the initial arc melted alloy. According to the total atom count by QPA, crystallisation of the Fe richer amorphous Zr 56Fe 44 phase formed at 330 °C begins at ca. 530 °C, and later by 680 °C, all amorphous phases have completely crystallised to yield a 70.77:26.75:2.47 mol.% mixture of Zr 3Fe:ZrFe 2:ZrD 2− x .

Crystal structure, coloring problem and magnetism of Gd5−xZrxSi4

Ternary Gd(5-x)Zr(x)Si(4) silicides were synthesized by arc melting of the constituent elements and subsequent heat treatments. The Gd(5-x)Zr(x)Si(4) phases adopt the orthorhombic Gd(5)Si(4)-type (space group Pnma) structure for x≤ 0.25 and the tetragonal Zr(5)Si(4)-type (space group P4(1)2(1)2) structure for x≥ 1.0, respectively. The samples with intermediate compositions contain two phases. Single-crystal X-ray diffraction reveals a preferential site occupancy for Zr on the three metal sites in the order of M3 > M2 > M1. Size arguments based on the local coordination environments suggest that the larger Gd atoms preferentially occupy the larger M1 site, while the smaller Zr atoms tend to occupy the smaller metal sites, M2 and M3. Tight-binding linear-muffin-tin orbital calculations illustrate a role of the metal-silicon bonds in the metal site occupation. An increase in the valence electron concentration through the Zr substitution weakens the Si-Si interactions but enhances the metal-silicon and metal-metal interactions. The Curie temperature of Gd(5-x)Zr(x)Si(4) decreases gradually with the increasing Zr content.

A study of spin-Hamiltonian parameters and defect structure for Nd3+ in ZrSiO4 crystal

The spin-Hamiltonian parameters ( g factors g ∥ , g ⊥ and hyperfine structure constants 143 A ∥ , 143 A ⊥ , 145 A ∥ , 145 A ⊥ ) for Nd 3+ ion at the tetragonal Zr 4+ site of ZrSiO 4 crystal are calculated from a diagonalization (of energy matrix) method. In the method, the Zeeman and hyperfine interaction terms are added to the conventional Hamiltonian and a 52×52 energy matrix is obtained for 4f 3 ions in tetragonal symmetry on the basis of the ground multiplet 4 I 9/2 and the first to third excited multiplets 4 I 11/2 , 4 I 13/2 and 4 I 15/2 . The calculated results are in reasonable agreement with the observed values. The defect structure of Nd 3+ center is determined and the signs of hyperfine constants 143 A i ( i =∥ or ⊥) and 145 A i are suggested from the calculations. The results are discussed.

Crystallization of Zr 60Fe 20Cu 20 amorphous alloy

Amorphous structure and phase transformations of the rapidly solidified Zr 60Fe 20Cu 20 alloy have been investigated by the DSC, in-situ high temperature XRD and EXAFS techniques. The performed experiments on the amorphous alloy proved significantly shorter Zr–Fe and Zr–Cu distances than those expected from the hard sphere atom model, corroborating strong bonding between Zr and transition elements. The crystallization of Zr 60Cu 20Fe 20 amorphous alloy underwent three-stage process. The formation of stable cubic Zr(Cu, Fe) and tetragonal Zr 2(Cu, Fe) phases was confirmed and the formation of a quasicrystalline phase was suggested.

Formation of Zr 66.7Al 11.1Ni 22.2 noncrystalline alloys demonstrated by molecular dynamics simulations based on distorted plastic crystal model

Molecular dynamics simulations with a scheme to treat groups of atoms in an intermetallic compound as a hypothetical cluster were performed for Zr–Ni base alloys by allowing random orientations of the clusters that were imitated to plastic crystals in a class of soft matter. A binary Zr 66.7Ni 33.3 and ternary Zr 66.7Al 11.1Ni 22.2 and Zr 66.7Al 22.2Ni 11.1 alloys were analyzed for their local atomic arrangements and forming ability of a noncrystalline structure with total pair-distribution and interference functions and Voronoi polyhedra. The analysis revealed that a Zr 66.7Al 11.1Ni 22.2 alloy created from the tetragonal Zr 2Ni structure by replacing Ni with Al reproduces the features of the local atomic arrangements of the experimental data for a Zr 60Al 15Ni 25 bulk metallic glass (BMG) in a supercooled liquid state while the alloy from the Zr 6Al 2Ni structure by substituting Al and Ni atoms agrees to the BMG in an as-quenched state.

Formation of nano-scale ω-phase in arc-melted micron-scale dendrite reinforced Zr 73.5Nb 9Cu 7Ni 1Al 9.5 ultrafine composite during heat treatment

An arc-melted Zr 73.5Nb 9Cu 7Ni 1Al 9.5 alloy consists of dendritic body-centered cubic solid solution and a mixture of ultrafine body-centered tetragonal Zr 2Cu-type and hexagonal close-packed MgZn 2-type phases in the ultrafine matrix. This composite exhibits two exothermic reactions upon heating to 973 K with a heating rate of 40 K/min. After the first exothermic reaction nano-scale ω-phase particles have formed in the β-phase dendrites indicating a decomposition of the supersaturated solid solution upon heating. At the early stage during the decomposition of the β-phase the ω-phase is coherent with the parent phase without clear structural differences. However, semicoherency between the β- and the nano-scale ω-phase regions was observed during the growth of the ω-phase. This structural semicoherency causes nano-scale twinning in the β-phase dendrites around the ordered ω-phase in order to release the mismatch energy at the interfaces between the ordered ω- and β-phases.

Influences of structure and composition on the photoelectrochemical behaviour of anodic films on Zr and Zr–20 at.%Ti

A photoelectrochemical investigation on anodic films of different thickness grown on sputter-deposited Zr and Zr–20 at.%Ti was carried out. The estimated optical band gap and flat band potential of thick ( U F ≥ 50 V) anodic films were related to their crystalline structure and compared with those obtained for thinner ( U F ≤ 8 V/SCE) anodic oxides having undetermined crystalline structure. The E g values obtained by photocurrent spectroscopy were also compared with the experimental band gap estimated by other optical ex situ techniques and with the available theoretical estimates of the zirconia electronic structures in an attempt to reconcile the wide range of band gap data reported in the literature. Finally, the optical band gap and flat band potential values obtained for tetragonal Zr 0.8Ti 0.2O 2 mixed oxide were compared with that expected on the basis of a correlation between E g and the film composition.

Effect of Al on the local structure and stability of Zr-based metallic glasses

The effect of Al addition on the local structure and the thermal stability in the Zr–Ni-based metallic glass is investigated. It is well known that Al is a very effective element on the enhancement of glass-forming ability (GFA), i.e., stability of supercooled liquid state in the alloy system. We have found that the dominant local structure is icosahedral-like in the Zr 70Al 10Ni 20 metallic glass and the tetragonal Zr 2Ni-like local in the Zr 70Ni 30 amorphous alloy. It is concluded that the change in the dominant local structure contributes to the enhancement of the stability of supercooled liquid state in the alloy.

Correlation between local structure and stability of supercooled liquid state in Zr-based metallic glasses

The correlation between the local structure and stability of supercooled liquid state is investigated in the Zr 70(Ni, Cu) 30 binary and Zr 70Al 10(Ni, Cu) 20 (numbers indicate at.%) ternary metallic glasses. The Zr 70Ni 30 binary amorphous alloy with a low stability of supercooled liquid state has a tetragonal Zr 2Ni-like local structure around Ni atom. Meanwhile, the Zr 70Cu 30 binary metallic glass has a different local structure of tetragonal Zr 2Cu, where we suggest the icosahedral local structure by the quasicrystallization behavior in addition of a very small amount of noble metals. The effect of Al addition on the local structure in the Zr–Ni alloy is also examined. We have investigated that the dominant local structure changes in the icosahedral-like structure from the tetragonal Zr 2Ni-like local structure by the Al substitution with Ni accompanying with the significant stabilization of supercooled liquid state. It is concluded that the formation of icosahedral local structure contributes to the enhancement of stability of supercooled liquid state in the Zr-based alloys.