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1
Content available remote Structure and electrical properties of oxide-ion conductors in the Bi3NbO7-Bi3YO6 system
Kozanecka-Szmigiel A., Krok F., Abrahams I., Wrobel W., Chan S.C.M., Dygas J.R.
Materials Science Poland
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2006
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Vol. 24, No. 1
31--37
EN
A study of the structure and electrical conductivity of Bi3Nb1-xYxO7-x is presented. X-ray diffraction confirms full solid solution formation in this system, with the adoption of a fluorite-type structure. Superlattice ordering of the anion sublattice is evident in neutron diffraction data, the nature of which varies with composition. At low values of x, long-range ordering is present, whereas above x = 0.4 only local ordering is observed. Arrhenius plots of the total electrical conductivity of all samples containing yttrium show two linear regions with different activation energies, with evidence for a phase transition between 450 and 680 °C.
2
Content available remote Structural and transport properties of LiFe0.45Mn0.55PO4 as a cathode material in Li-ion batteries
Ojczyk W., Marzec J., Dygas J., Krok F., Liu R.S., Molenda J.
Materials Science Poland
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2006
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Vol. 24, No. 1
103--113
EN
The paper presents investigations on structural, electrical and electrochemical properties of phosphoolivine, LiFe0.45Mn0.55PO4, synthesized at high temperatures. Moessbauer spectroscopy measurements confirmed the occurrence of iron(II), and X-ray absorption near edge structure (XANES) measurements evidenced manganese(II) and iron(II). Impedance spectroscopy enabled the separation of electrical conductivity into electronic and ionic components. The substitution of manganese for iron led to a noticeable increase in the electronic component of conductivity and only to a slight increase in the ionic component, compared to pure LiFePO4. Also, the chemical diffusion coefficient of lithium measured by GITT turned out larger in LixFe0.45Mn0.55PO4. It has been stated that the increased electronic conductivity in manganese-doped phospho-olivine activates the diffusional mechanism of lithium deintercalation.
3
Content available remote Oxide-ion conductors for fuel cells
Krok F., Abrahams I., Wrobel W., Kozanecka-Szmigiel A., Dygas J.R.
Materials Science Poland
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2006
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Vol. 24, No. 1
13--22
EN
The principal materials used in the construction of solid oxide fuel cells (SOFCs) are discussed. Some of the problems encountered with high temperature fuel cells (HT-SOFCs) might be overcome by lowering the operating temperature to 500-700 °C, through the development of suitable materials for intermediate temperature fuel cells IT-SOFCs. Candidate electrolyte materials are discussed, including cerium gallium oxide, lanthanum strontium gallium magnesium oxide, and electrolytes based on doped bismuth oxide. While high ionic conductivities can readily be achieved in these materials at intermediate temperatures, stability in reducing atmosphere is still a problem. This might be overcome by careful chemical design of electrolytes containing stabilising dopants. Two zirconia-doped bismuthate systems are discussed in this respect. In both cases, the obtained materials exhibit different structures - one is Bi3Nb1-xZrxO7-x/2 of the ?-Bi2O3 type, and the other, Bi4V2-2xZrxO11-x, has a layered structure of the Aurivillius type.
4
Content available remote Ionic conductivity of polymer electrolytes comprising acrylonitrile-butyl acrylate copolymer and a lithium salt
Łasińska A., Dygas J.R., Krok F., Marzantowicz M., Florjańczyk Z., Tomaszewska A., Zygadło-Monikowska E.
Materials Science Poland
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2006
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Vol. 24, No. 1
187--194
EN
New polymer electrolytes were prepared by mixing random copolymers of acrylonitrile and butyl acrylate (poly(AN-co-BuA)) with lithium bis(trifluoromethanesulfone) imide (LiTFSI). Electrical properties were studied by the impedance spectroscopy. The glass transition temperature was studied by DSC. Presented results concern a broad range of compositions, from a pristine copolymer to the system with 98 wt. % of salt. Correlation was established between the glass transition temperature, ionic conductivity, and salt content in the system. Mixtures of poly(AN-co-BuA) and LiTFSI exhibit much lower glass transition temperatures than the parent copolymer. Effects of ageing were observed for electrolytes with high salt content.
5
Content available remote In-situ study of the influence of crystallization on the ionic conductivity of polymer electrolytes
Marzantowicz M., Dygas J.R., Krok F., Zygadło-Monikowska E., Florjańczyk Z.
Materials Science Poland
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2006
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Vol. 24, No. 1
195--203
EN
Simultaneous impedance measurements and optical observations of polymer electrolytes were conducted in an automated experimental setup, combining an impedance analyser, polarizing microscope with a heating stage and a digital camera. The polymer film was placed between glasses with indium tin oxide conductive layers, forming a transparent cell mounted in a custom-designed holder, which preserved an argon atmosphere. Results of in-situ studies for various compositions of poly(ethylene oxide) (PEO) with LiN(CF3SO2)2 salt (LiTFSI), as well as pure PEO, are presented. In the investigated systems, crystallization had a strong impact on ionic conductivity. It was found that the initial growth of crystalline structures caused only a small fraction of the total decrease of conductivity. A large decrease in conductivity was observed during the second stage of crystallization, when no significant changes in microscope picture were observed. In pure PEO and the PEO:LiTFSI 6:1 system, a dense crystalline structure developed, resulting in a decrease in conductivity of over two orders of magnitude. In dilute PEO:LiTFSI systems, a "loose" structure was formed, with amorphous areas preserved between crystallites, and conductivity decreased by only a factor of about 6.
6
Content available remote Bi8V2O17 - a stable phase in the Bi2O3-V2O5 system
Wrobel W., Krok F., Abrahams I., Kozanecka-Szmigiel A., Malys M., Chan S.C.M., Dygas J.R.
Materials Science Poland
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2006
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Vol. 24, No. 1
23--30
EN
Bi8V2O17 is commonly observed as an intermediate phase in the synthesis of compounds in ternary systems of the type Bi2O3-V2O5-MexOy. It is also seen as an end product at particular compositions in these systems. A rhombohedral substructure model for this phase is presented along with electrical parameters. Evidence from the Arrhenius plot suggests a phase transition at around 550 °C. The existence of a limited solid solution of Bi8V2O17 with ZrO2 is also discussed.
7
Content available remote Low energy ion beam-induced modification of InSb surface studied at nanometric scale
Krok F., Kołodziej J.J., Such B., Piątkowski P., Szymoński M., Odendaal R.Q., Malherbe J.B.
Optica Applicata
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2002
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Vol. 32, nr 3
221-226
EN
Atomically flat InSb(001) surface has been prepared with cycles of sputter-cleaning and annealing. The surface structure has been characterized by low energy electron diffraction (LEED) and by atomic force microscopy (AFM). Then the surface has been bombarded with 4 keV Ar+ ions incident 50° off normal, and the morphological changes have been studied with the AFM as a function of the ion dose. It was found that the surface was amorphized already for low ion doses (~2×1015/cm2). At higher ion doses (of 2×1016/cm2) the surface appeared to be covered with the system of parallel nanowires running along surface projection of the ion beam direction. Typical sizes of the nanowires were: 1.5–2 mm length, 50–70 nm width and height 5–7 nm.
8
Modyfikacja powierzchni w procesie elektronowo symulowanej desorpcji
Such B., Kołodziej J., Krok F., Meisel K., Czuba P., Piątkowski P., Struski P., Szymoński M.
Elektronika : konstrukcje, technologie, zastosowania
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2001
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Vol. 42, nr 8-9
48-50
EN
Alkali halide surface modification due to electron irradiation was investigated with the use of dynamic force microscopy (DFM) and quadrupole mass spectroscopy (QMS). As a result of desorption of atoms from the surface, rectangular pits are created in the topmost layer of the crystal. During irradiation the pits are growing and linking with others what leads to layer-by-layer desorption. Desorption yields of both components exhibit oscillatory dependence on the dose of impinging electrons. Moreover, a correlation has been found between the number of low-coordinated sites on the surface and desorption efficiency. The model is proposed, in which the phenomenon is explained by creation of dynamic equilibrium between competitive processes: (i) desorption and recombination of pairs of defects and (ii) accumulation of F centres in proximity of the surface, which is directed by the topography of the surface.
9
Atomic force microscopy imaging of the paper surface subjected to process of artificial ageing
Krok F., Piątkowski P., Czuba P., Konieczna A., Barański A., Szymoński M.
Electron Technology
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2000
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Vol. 33, No. 3
361-365
EN
The influence if the ageing process on the paper surface topography has been examined by means of the Atomic Force Microscopy (AFM). The AFM images of thr native and artificially aged paper exhabit different surface strucure and various abilities to bond water. The surface of native paper consist of the cellulose macrofibres with a spine-like structure, and the elementary fibres of about 10 ÷ 20 nm in diameter. It was found that the ageing process did not change the spine-like structure of the cellulose macrofibres, although it induced the swelling of the elementary fibres. In addition, the images of the aged paper showed that multilayers of water were formed on its surface whereas for non-aged samples such effect was not observed. This behaviour was confirmed by using a technique of "phase-imaging". We argue that swelling of the cellulose fibres and formation of water multilayers is caused by water molecules which are permanently bound to the cellulose chains of the aged paper.
10
Content available remote Przemysł górniczo-hutniczy rejonu olkuskiego
Krok F.
Przegląd Górniczy
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1999
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T. 55, nr 12
41-43
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