Atomic Volume

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M Ellner - One of the best experts on this subject based on the ideXlab platform.

  • Crystal chemical investigation of the solid solutions of antimony and bismuth in palladium and platinum
    Journal of Alloys and Compounds, 2006
    Co-Authors: M Ellner
    Abstract:

    Abstract Unit cell parameters were measured for the solid solutions Pd(Sb), Pd(Bi) and Pt(Sb) in the whole range of homogeneity. The composition dependence of the average Atomic Volume was investigated for the binary systems Pd–Sb and Pd–Bi. For the solid solutions Pd(Sb) and Pd(Bi), the partial Atomic Volumes of antimony and bismuth were determined. They are compared with the partial Atomic Volumes of the 4d (Ag⋯Te) and 5d (Au⋯Pb) elements measured in the palladium-based solid solutions. The increase in the partial Atomic Volume for the 4d elements Ag and Sb amounts to 16.3%, for the analogous heavy elements Au and Bi to 26.1%.

  • partial Atomic Volume and partial molar enthalpy of formation of the 3d metals in the palladium based solid solutions
    Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2004
    Co-Authors: M Ellner
    Abstract:

    The composition dependence of the average Atomic Volume, as well as of the enthalpy of formation, was investigated for the palladium-containing binary systems with the 3d metals. The partial Atomic Volume and the partial molar enthalpy of formation of the 3d metals were determined for the palladium-based solid solutions (Pearson symbol cF4, space group \(Fm\bar 3m\), Cu type). The 3d early transition metals (scandium, titanium, and vanadium) as well as the 3d104s2 … 3d104s24p metals (zinc and gallium) show (1) the partial Atomic Volume for the palladium-based solid solutions smaller than is their Atomic Volume in the nonbonded state and (2) significantly large (negative) values of the partial molar enthalpy of formation indicating a strong bond energy between atoms of palladium and those of the 3d early transition metals (as well as a strong bond energy between atoms of palladium and zinc or gallium atoms). The 3d late transition metals (and chromium) show (1) the partial Atomic Volume for the palladium-based solid solutions larger than is their Atomic Volume in the nonbonded state and (2) low (negative) values of the partial molar enthalpy of formation indicating weak bond energy between atoms of palladium and those of the 3d late transition metals.

  • Partial Atomic Volume of Early Transition Metals in A10 Metal-Based Solid Solutions
    Zeitschrift für Metallkunde, 2004
    Co-Authors: M Ellner
    Abstract:

    Unit-cell parameters were measured for the A 10 metal-based (= Ni, Pd, Pt) solid solutions (Pearson symbol cF4, space group Fm3m, Cu type) with the A 5 transition metals (V, Nb, Ta) in the whole range of homogeneity. Composition dependence both of the average Atomic Volume and the enthalpy of formation were investigated for the A 10 metal-based solid solutions with the A 5 and A 6 transition metals; the partial Atomic Volume and the partial molar enthalpy of formation of the A 5 and A 6 transition were determined for the A 10 -rich terminal phases. Among the systems investigated, only the solid solutions Pd(Cr) and Pt(Cr) show partial Atomic Volume of chromium larger than the chromium Atomic Volume. In the nickel-based solid solution, the partial Atomic Volume of chromium is equal to the chromium Atomic Volume. The partial molar enthalpy of formation for the A 5 transition metals - in the nickel, palladium and platinum-rich alloys - shows larger negative values than values evaluated for the A 6 transition metals. An enlarged investigation of the data available in literature shows that both the relative Volume change, resulting from the dissolving process of the early transition metals in the A 10 metal-based alloys, and the negative values of the partial molar enthalpy of formation increase with decreasing number of the 3d and 4d electrons of the early transition elements. For the 5d quasihomologous transition metals, this observation is valid for the A 4 ... A 6 elements as well.

  • Bond energy in palladium and platinum-rich alloys with the A4 transition metals
    Journal of Alloys and Compounds, 2003
    Co-Authors: M Ellner
    Abstract:

    Abstract Unit cell parameters were measured for the binary palladium and platinum-rich alloys containing the A 4 early transition metals (titanium, zirconium and hafnium). The composition dependence of the average Atomic Volume was investigated for the whole composition range of these binary systems. For the palladium and platinum-rich portions, the partial Atomic Volume and the partial molar enthalpy of formation are discussed. Both the Volumetric and the thermodynamic quantities reveal a strong bond energy between atoms of the heavy A 4 transition metals (zirconium and hafnium) and the heavy A 10 transition metals (palladium and platinum).

  • On the partial Atomic Volume of aluminum in solid solutions based on the 3d transition metals and copper
    Metallurgical and Materials Transactions A, 2002
    Co-Authors: M Ellner, I. Park
    Abstract:

    The composition dependence of the average Atomic Volume, as well as of the enthalpy of formation, was investigated for the aluminum-containing systems with the 3d transition metals and copper. The partial Atomic Volume of aluminum and the partial molar enthalpy of aluminum were determined for the transition metal-based solid solutions. Independent of the type of solid-solution structure, the (negative) partial molar enthalpy of aluminum increases and the partial Atomic Volume of aluminum decreases with increasing filling of the 3d band. The charge transfer and the bonding in solid solutions exhibiting close-packed structures (coordination number (CN)=12) is substantially higher than in solid solutions, based on the bcc structure (CN=8). The s electron of copper, though, reduces the charge transfer and the bonding in the fcc solid-solution Cu(Al) significantly.

Tomasz Czujko - One of the best experts on this subject based on the ideXlab platform.

Robert A. Varin - One of the best experts on this subject based on the ideXlab platform.

A Giridhar - One of the best experts on this subject based on the ideXlab platform.

  • Mean Atomic Volume and Tg of Cu-Ge-As-Se glasses
    Journal of Non-crystalline Solids, 2000
    Co-Authors: Sudha Mahadevan, A Giridhar
    Abstract:

    Results of measurements of the mean Atomic Volume (V), the glass transition temperature (Tg) and the activation energy for glass transition (Et) are reported for 11 glass compositions of the Cu-Ge-As-Se system. The compositions studied can be represented as Cux(Ge0.125As0.25Se0.625)100-x glasses. In the V-x, Tg-x and the Et-x data of these glasses, changes in slope are observed at an x value of approximately 2. The results are consistent with a picture wherein, up to approximately 2 Atomic percent (at.%), Cu atoms occupy interlayer positions between the uncorrelated layers of the parent glass matrix without affecting either the medium or the short range ordering of the parent glass. The results also suggest that up to approximately 2 at.%, Cu atoms act as `plasticizers' in the parent glass matrix, reducing its Tg.

  • Mean Atomic Volume and Tg of Agx(As0.4Se0.3Te0.3)100−x glasses
    Journal of Non-Crystalline Solids, 1999
    Co-Authors: Sudha Mahadevan, A Giridhar
    Abstract:

    Results of measurements of the mean Atomic Volume(V) and the glass transition temperature (Tg) for ten glass compositions of the As-Se-Te-Cu system have been reported and discussed. The compositions studied can be represented as Cux(As0.2Te0.4)100-x glasses, with the Cu content varying from 5 to 25 Atomic precent (at%) In the V-x and Tg-x data a change in shape is observed at the composition with a Cu content of 16.67 at % A model seconding to which, with progressive increase in the Cu content, formation of CuAsSe2 abd CuAsTe structural units begin to form in place of some of the original As,Se,and As2Te2 structural units of the parent glass, is able to account satisfactorily the change in slope at a Cu content of 16.67 at % The persent results strengthen our earlier conclusions (1) from a study of the Cux(As0.4Se0.3Te0.3)100-x glasses

  • mean Atomic Volume tg and electrical conductivity of cux as0 4te0 6 100 x glasses
    Journal of Non-crystalline Solids, 1998
    Co-Authors: A Giridhar, Sudha Mahadevan
    Abstract:

    Abstract Results of measurements of the mean Atomic Volume (V), the glass transition temperature (Tg) and the electrical conductivity (σ) on 12 compositions of the Cux(As0.4Te0.6)100 − x glasses, with x from 0 to 20 at.%, are reported and discussed. A reduction in V and a constancy of Tg are observed as Cu varies from 0 to 3 at.%. To this stage, the Cu atoms occupy interlayer positions in the layered network of the parent As0.4Te0.6 glass. The σ of glasses with ⩽3 at.% of Cu, are less than that of the parent glass. For Cu>3 at.%, Cu forms bonds with Te and the glasses become regular three component As–Te–Cu glasses. Due to this bonding, changes in slope occur in the V as a function of composition and Tg as a function of composition at Cu content of 3 at.%. The results are examined using a model which envisages the formation of Cu2Te, As2Te3 and As structural units in these glasses. For Cu>3 at.%, a decrease of the conductivity activation energy and an increase of σ occur with increasing Cu content.

  • Mean Atomic Volume, Tg and electrical conductivity of Cux(As0.4Te0.6)100−x glasses
    Journal of Non-Crystalline Solids, 1998
    Co-Authors: A Giridhar, Sudha Mahadevan
    Abstract:

    Abstract Results of measurements of the mean Atomic Volume (V), the glass transition temperature (Tg) and the electrical conductivity (σ) on 12 compositions of the Cux(As0.4Te0.6)100 − x glasses, with x from 0 to 20 at.%, are reported and discussed. A reduction in V and a constancy of Tg are observed as Cu varies from 0 to 3 at.%. To this stage, the Cu atoms occupy interlayer positions in the layered network of the parent As0.4Te0.6 glass. The σ of glasses with ⩽3 at.% of Cu, are less than that of the parent glass. For Cu>3 at.%, Cu forms bonds with Te and the glasses become regular three component As–Te–Cu glasses. Due to this bonding, changes in slope occur in the V as a function of composition and Tg as a function of composition at Cu content of 3 at.%. The results are examined using a model which envisages the formation of Cu2Te, As2Te3 and As structural units in these glasses. For Cu>3 at.%, a decrease of the conductivity activation energy and an increase of σ occur with increasing Cu content.

  • Cu as an additive in the As0.4Se0.2Te0.4 glass: mean Atomic Volume and Tg
    Journal of Non-crystalline Solids, 1997
    Co-Authors: Sudha Mahadevan, A Giridhar
    Abstract:

    Data on the mean Atomic Volume (V) and the glass transition temperature (Tg) of the As0.4Se0.3Te0.3 glass, modified with Cu are reported and discussed. The V and Tg of the parent glass are invariant with addition of ≤1 Atomic percent (at.%) of Cu up to which clusters of Cu atoms occupy interlayer positions in the layered network of the parent glass. For additions of Cu>1 at.%, a decrease in V and an increase in Tg are observed. The composition dependencies of V and Tg are consistent with a model according to which, with progressive increase in the Cu content, some of the original As2Se3 and As2Te3 structural units of the parent glass are replaced, respectively, by CuAsSe2 and CuAsTe structural units. For Cu≥23.08 at.%, after the formation of CuAsSe2 structural units, there is no free Se available for the formation of As2Se3 structural units; as no free Se is available, a change of slope occurs in the V–composition and Tg–composition data at the Cu content of 23.08 at.%. The increase in Tg with increasing Cu content is due to an increase in the average coordination number brought about by an increase in cross linking due to the formation of tetrahedral CuAsSe2 and CuAsTe complexes in the glasses.

Hanns-peter Liermann - One of the best experts on this subject based on the ideXlab platform.

  • Influence of the critical Fe Atomic Volume on the magnetism of Fe-rich metallic glasses evidenced by pressure-dependent measurements
    Physical Review B, 2016
    Co-Authors: L. F. Kiss, T. Kemény, Jozef Bednarcik, Jana Gamcová, Hanns-peter Liermann
    Abstract:

    Despite the intensive studies for decades, it is still not well understood how qualitatively different magnetic behaviors can occur in a narrow composition range for the Fe-rich Fe-transition metal (TM) amorphous alloys. In this study of amorphous Fe$_{100−x}$Zr$_x$ (x=7, 9, 12) metallic glasses, normal ferromagnetism (FM) is found at 12 % Zr where only the FM-paramagnetic (PM) transition is observed at the Curie temperature, T$_C$. In contrast, spin-glass (SG)-PM transition at a temperature, T$_g$, called SG temperature, is only observed at 7 % Zr, while in the transient re-entrant composition range (x=8−11), an SG-FM transition at a temperature, T$_f$, called spin-freezing temperature, is also observed at low temperature besides the normal FM-PM transition at T$_C$. In order to understand this unusual behavior, a detailed characterization of pressure (Atomic Volume), composition, and temperature dependence of the magnetic properties is coupled with high pressure synchrotron x-ray diffraction determination of the pressure dependence of the Atomic Volume. The results on Fe$_{100−x}$Zr$_x$(x=7, 9, 12) are compared to those obtained for the FM Co$_{91}$Zr$_9$ metallic glass not showing any kind of anomalous magnetic properties. It is confirmed that the unusual behavior is caused by a granularlike magnetic structure where weakly coupled magnetic clusters are embedded into a FM bulk matrix. Since the mechanism of the magnetization reversal was found to be of the curling type rather than homogeneous rotation, the energy barrier determining the blocking temperature of the clusters is calculated as AR, where A is the exchange constant and R is the cluster size, in contrast to the usual characterization of the energy barrier by KV where K is the anisotropy energy and V is the cluster Volume. The Volume fraction of the FM part is a fast changing function of the bulk composition: Almost 100% FM fraction is found at 12 % of Zr while no trace of real FM is observed at 7 at % Zr. The driving force of this surprising magnetic character is the Atomic Volume: The lower the Zr content, the higher is the fraction of Fe atoms with compressed Atomic Volume having low magnetic moment. The percolation of their network separates the clusters from the FM bulk. The complex magnetic behavior of the Fe-rich Fe-Zr amorphous system at low temperatures can thus be interpreted with the only assumption of a cluster-size distribution and a weak coupling of the clusters to the FM matrix. The introduction of this coupling is able to explain the opposite pressure dependence of T$_g$ and T$_f$. The threshold Atomic Volume in the low magnetic moment regions is found to be comparable to the Atomic Volume characteristic to the low-spin limit of the face-centered-cubic Fe alloys. The extensive literature results on the anomalous magnetism for various Fe-rich Fe-TM amorphous alloys and especially for the Fe-rich Fe-Zr glassy system are also found to be in agreement with this granular magnetic behavior