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1
Content available remote

Thermoelectric Promise of (In_xSn_x)Co_4Sb_{12} Materials

100%
Godart C., Lopes E., Gonçalves A.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
403-406
EN
We report on a new series of filled skutterudites derived from CoSb_3 with double filling of the cage (by In, Sn) in order to lower the thermal conductivity. As expected for Co-rich side samples, the Seebeck coefficient indicates n-type, with surprisingly high values at 300 K.
2
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Discrete Tomography: Magic Numbers for N-Fold Symmetry

100%
Huck C., Moll M., Nilsson J.
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vol. 126
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issue 2
486-489
EN
We consider the problem of distinguishing convex subsets of n-cyclotomic model sets Λ by (discrete parallel) X-rays in prescribed Λ-directions. In this context, a 'magic number' m_{Λ} has the property that any two convex subsets of Λ can be distinguished by their X-rays in any set of m_{Λ} prescribed Λ-directions. Recent calculations suggest that (with one exception in the case n=4) the least possible magic number for n-cyclotomic model sets might just be N+1, where N=lcm(n,2).
3
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Ionic Conductivity in Multiphase Li₂O-7GeO₂ Compounds

80%
Nesterov O., Trubitsyn M., Nedilko S., Volnianskii M., Plyaka S., Rybak Y.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
892-896
EN
Crystallization of Li₂O-7GeO₂ glass was carried out on heating, simultaneously differential scanning calorimetry and electric properties were studied. Morphology of the phase states obtained at glass devitrification was examined by atomic force microscopy. It was shown that amorphous phase of Li₂O-7GeO₂ was crystallized in stages through the intermediate state with increased conductivity σ . In the intermediate state the sample volume was occupied by nanometer-sized nuclei with ordered structure surrounded by internuclear amorphous medium. Complete glass crystallization occurred through transformation of nanometer-sized nuclei into micrometer-sized crystallites and was accompanied by a sharp and irreversible decrease of conductivity. Atomic force microscopy of the samples heat-treated in different ways showed that Li₂O-7GeO₂ glass crystallization was suppressed near the surface and mainly proceeded within the sample bulk. Charge transfer in amorphous, nanocrystalline intermediate and polycrystalline phases of Li₂O-7GeO₂ was associated with motion of the weakly bound Li ions.
4
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Mechanical Alloying - a Novel Method for Synthesis and Processing of Materials

80%
Oleszak D.
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vol. 96
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issue 1
101-112
EN
High energy ball milling (mechanical alloying) has recently become a popular research topic. As the non-equilibrium processing method, this technique may be used for the synthesis of many materials, including metastable ones. In many cases these materials exhibit the structure and properties quite different from materials prepared by conventional methods. In this paper some examples of metastable structures synthesized by mechanical alloying are described. The results of mechanical alloying in the Fe-Al system are presented as well.
5
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Disorder and Diffusion in Mayenite

80%
Boysen H., Kaiser-Bischoff I., Lerch M., Berendts S., Hoelzel M., Senyshyn A.
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issue 1
38-41
EN
Mayenite, Ca_{12}Al_{14}O_{33}, has attracted enormous attention for novel technological applications after the discovery of its high oxygen ionic conductivity. The crystal structure consists of a calcium-aluminate framework, comprising 32 of the 33 oxygen anions. The remaining oxygen is distributed over 1/6 of large cages within the framework. The true structure is heavily disordered and usually non-stoichiometric due to the presence of extra anions and is presented for four samples: pure oxygen mayenite (O-mayenite), partly (O/N-mayenite) and fully (N-mayenite) exchanged by nitrogen and doped with iron (Fe-mayenite). All samples were investigated by neutron powder diffraction up to 1050°C. Data were analysed by the Rietveld method and by difference Fourier methods. As prepared O-mayenite contains O_{2}^{-} and OH^{-}, N- and O/N-mayenite also NH_{2}^{-}, NH^{2-} and N^{3-}, while Fe-mayenite was free of extra radicals. In O- and N-mayenite the extra species are lost under vacuum conditions above ca. 700°C, whereas O/N-mayenite retained NH_{2}^{-} up to high temperatures. Diffusion of oxygen proceeds via a jump-like interstitialcy process involving exchange of the "free" oxygen with framework oxygen, coupled to relaxations of Ca ions. In O/N-mayenite NH_{2}^{-} diffuses via interstitial process. In Fe-mayenite encaged oxygen is "invisible" due to extreme delocalisation or loss.
6
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How Random Is a Random Polymer Coil?

80%
Zając W.
Acta Physica Polonica A
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2012
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vol. 121
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issue 2
464-467
EN
Short range order within amorphous, random polymer structures is a well known and widely studied property of disordered systems. An aggregate of five random atactic chains, each comprising 400 building units was computer-generated and then used to calculate neutron coherent scattering intensity for 0.01 < Q < 30 nm^{-1} (0.001 < Q < 3 Å^{-1}). The latter was compared with experimental data within the diffuse scattering range. On the grounds of quantum chemical calculations for an atactic polystyrene tetramer and the above information it is concluded that interactions among phenyl rings are responsible for the onset of the local order in this polymer.
7
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The Moment Series Expansion for Quasicrystal with Phason Disorder

80%
Buganski I., Strzalka R., Wolny J.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
833-835
EN
The novel method for structural analysis of quasicrystals with phason flips is presented. The correction for diffraction peaks' intensities can be made within average unit cell approach by modification of the statistical distribution of atomic positions. Characteristic function of the distribution expanded into moment series, involving only even moments, estimates the envelope function and therefore the flip ratio can be evaluated.
8
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Structural Stabilities and Elastic Constants of EuX (X = O, S, Se, and Te) Compounds at High Pressure

80%
Kong B., Zhou Z., Sun X., Zhang L., Ling-Hu R.
Acta Physica Polonica A
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2013
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vol. 123
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issue 4
720-727
EN
The structural stabilities, elastic properties and charge transfers of EuX (X = O, S, Se, Te) compounds as a function of pressure are investigated extensively using first-principles calculations. The ground-state parameters, such as lattice constants, bulk modulus are predicted and compared with the available data, our results are satisfactory. The calculated phase transition pressures from the NaCl-type (B1) structure to the CsCl-type (B2) structure for EuX (X = O, S, Se, Te) also accord with the experiments. Particularly, the elastic constants of EuX (X = O, S, Se, Te) under zero pressure and high pressure are simulated appropriately for the first time via density functional theory. The softening behaviors of the elastic shear modulus C_{44} under pressure for the B1 phase of EuX (X = O, S, Se, Te) are captured, which should be responsible for the pressure-induced structural phase transition in the EuX system. It is also suggested that the softening behavior might be induced partly by the p → d and f → d electron transfers of Eu atom under pressure. In addition, the aggregate elastic modulus (B, G, E), Poisson's ratio (σ), Debye temperature Θp_{D} are also successfully obtained for both B1 and B2 phases of EuX.
9
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Study of the Effect of Boron Concentration on Magnetic and Structural Properties of Nd_{7.5}Pr_{2.5}Fe_{90-x}B_x Melt-Spun Alloys

80%
Siddique M., Ahmad I., Kanwal M., Ahmed E.
Acta Physica Polonica A
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2015
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vol. 128
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issue 3
353-357
EN
The Mössbauer spectroscopy and X-ray diffraction techniques have been used to investigate the effect of boron concentration on the structural and magnetic properties of as-quenched and heat-treated melt-spun alloys Nd_{7.5}Pr_{2.5}Fe_{90-x}B_x (x=6, 8, 10) produced by melt-spinning technique. X-ray diffraction and Mössbauer spectroscopy results indicate that as-prepared samples are completely amorphous in nature. The X-ray diffraction patterns of samples heat-treated at 700°C are indexed as Fe_{3}B, α -Fe, (NdPr)_{2}Fe_{14}B and Fe_{23}B_{6} phases. The Mössbauer spectra of heat-treated samples are very complex and constituted a number of sextets and a quadrupole doublet. Two main phases are (NdPr)_{2}Fe_{14}B hard and t-Fe_{3}B soft magnetic phases while α -Fe and Nd_{23}Fe_{6} are detected as minor phases. The average internal magnetic field decreases with the increase of boron content; more sharply in as-prepared and comparatively slowly in heat-treated samples. The X-ray diffraction and Mössbauer spectroscopy results are in good agreement with each other.
10
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Scaling of the Thue-Morse Diffraction Measure

80%
Baake M., Grimm U., Nilsson J.
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vol. 126
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issue 2
431-434
EN
We revisit the well-known and much studied Riesz product representation of the Thue-Morse diffraction measure, which is also the maximal spectral measure for the corresponding dynamical spectrum in the complement of the pure point part. The known scaling relations are summarised, and some new findings are explained.
11
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Characterization of Structural Properties of LiM_xFe_{5-x}O_8 (M=Al, Cr, Mn), Spinel Solid Solutions

80%
Darul J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 2
367-373
EN
The structural properties of series spinel oxides with the general formula, LiM_{0.5}Fe_{4.5}O_8 (M = Mn, Cr, Al), are investigated. The effect of limited substitution of manganese, chromium and aluminum ions in the lithium ferrite samples on the order-disorder phase transition in the spinel crystal lattice at room temperature is presented. In these materials it is found that the ordered structures have not been isolated as single phases under the present experimental conditions and this fact will certainly influence the magnetic behavior of the compounds. The Rietveld refinements of the synchrotron X-ray diffraction data revealed that transition metal ions hinders the ordering process and Al^{3+} ion was shown to be least effective in removing of order.
12
Content available remote

Dynamical Properties of k-Free Lattice Points

80%
Huck C., Baake M.
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vol. 126
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issue 2
482-485
EN
We revisit the visible points of a lattice in Euclidean n-space together with their generalisations, the k-th-power-free points of a lattice, and study the corresponding dynamical system that arises via the closure of the lattice translation orbit. Our analysis extends previous results obtained by Sarnak and by Cellarosi and Sinai for the special case of square-free integers and sheds new light on previous joint work with Peter Pleasants.
13
Content available remote

Laboratory Dispersive EXAFS Spectrometer

80%
Mosset A., Lecante P., Baules P., Jaud J., Galy J., Burian A.
Acta Physica Polonica A
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1997
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vol. 91
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issue 4
825-828
EN
We report on a laboratory EXAFS spectrometer optimized for transmission dispersive mode. Absorption edges ranging from 6 to 20keV can be studied. Factors determining energy range and resolution are detailed. A new asymmetric geometry which allows to use all the lattice planes of the dispersing crystal is described and the choice of the best plane analysed. EXAFS spectra of Cu metal and Cu acetate, obtained on this laboratory facility, are compared to the corresponding spectra recorded on the French synchrotron facility (LURE).
14
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Recent Progress in Mathematical Diffraction

80%
Grimm U., Baake M.
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vol. 126
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issue 2
474-478
EN
A brief summary of recent developments in mathematical diffraction theory is given. Particular emphasis is placed on systems with aperiodic order and continuous spectral components. We restrict ourselves to some key results and refer to the literature for further details.
15
Publication available in full text mode
Content available

Structure Factor for Quasicrystals - 1D Case

80%
Kozakowski B., Wolny J.
Acta Physica Polonica A
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2003
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vol. 104
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issue 1
55-66
EN
Using a statistical approach a simple formula for the structure factor of decorated Fibonacci chain was derived. Although the used method operates in the physical space only, its equivalence to the higher-dimensional analysis was proved. Applications of the analysis to different decorated structures were also discussed.
16
Content available remote

Short Range Order in Polymers within Neutrons' Eyeshot

80%
Zając W.
Acta Physica Polonica A
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2009
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vol. 115
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issue 2
594-598
EN
The paper presents a short review of neutron scattering results obtained during investigation of short range order in bulk polymers. Neutron scattering proves exceptionally powerful in this type of study through (i) large penetration depth of bulk samples, (ii) isotope sensitivity, and (iii) the use of spin polarization technique. The examples provided deliver results that can hardly be obtained from e.g. X-ray diffraction.
17
Content available remote

Study of Local Structure of Fe_{84}B_{16} Amorphous Alloy by Electron Diffraction

80%
Hrabčáková V., Michalik Š., Borisenko K., Girman V., Nemcová V., Sovák P.
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vol. 126
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issue 1
130-131
EN
Local atomic structure in Fe_{84}B_{16} metallic glass, prepared by melt-spinning technique in He atmosphere, was studied by electron diffraction (ED) reduced density function (RDF) analysis. RDF curves were also obtained from X-ray diffraction (XRD) patterns and compared with the data from ED. Atomic reduced density functions, G(r), calculated from ED and XRD patterns showed good agreement. Atomic structure model has been fitted to the experimental ED data using Reverse Monte Carlo (RMC) simulation.
18
Content available remote

Structure Refinement of Amorphous Cd-As by Analysis of Partial Radial Distribution Functions

80%
Burian A.
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EN
The anomalous wide angle X-ray scattering technique was used to determine the partial structure factors and then the partial radial distribution functions for vacuum evaporated Cd-As amorphous films containing 41 and 74% at. As. The experiments were performed using synchrotron radiation tuned near the As and Cd absorption edges. The obtained structural information about the individual Cd-Cd, Cd-As and As-As correlations shows that As and Cd remain almost tetrahedrally coordinated and suggest a certain degree of chemical disorder of the investigated samples.
19
Publication available in full text mode
Content available

Spectroscopic Ellipsometry of Porphyrin Adsorbed in Porous Silicon

80%
Babonas G., Snitka V., Rodaitė R., Šimkienė I., Rėza A., Treideris M.
Acta Physica Polonica A
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2005
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vol. 107
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issue 2
319-323
EN
Aqueous solution of meso-tetra(4-sulfonatophenyl)porphine was deposited on electrochemically etched n-Si wafers. The morphology of the hybrid systems was investigated by scanning electron microscope and atomic force microscope techniques. The optical response of the hybrid systems was studied by spectroscopic ellipsometry in the range of 1-5 eV. Particular features in adsorption process were revealed for meso-tetra(4-sulfonatophenyl)porphine deposited on variously chemically treated Si substrates. It was found that porphyrin J-aggregates can be intercalated into large pores formed in a bulk n-Si as well as into nanopores of luminescent oxide layer.
20
Content available remote

Analysis of Chemical Disorder in Pb_{1-x}Ge_{x}Te

80%
Radzyński T., Łusakowski A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1317-1322
EN
The PbGeTe crystal lattice is locally deformed due to different ionic radii of cations and their random placement in the lattice. It is important to quantitatively characterize such microscopic disorder because local deformations have significant influence on the properties of magnetic ions introduced to such crystal. The simples method to study microscopic disorder is to consider purely classical model of the lattice in which neighboring atoms are connected by springs with properly chosen spring constant and equilibrium lengths. In the present work, using ab initio methods we discuss applicability of the springs-atoms model to the real crystal. We also explain results of extended X-ray absorption fine structure experiments performed on PbGeTe mixed crystals.
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