Józef Dygas - Academia.edu (original) (raw)

Papers by Józef Dygas

Superionic Conductor Physics - Proceedings of the 1st International Discussion Meeting on Superionic Conductor Physics, 2007

Materials for Lithium-Ion Batteries, 2000

Solid State Ionics, 2005

The impedance of the polycrystalline oxide ion conductor BIMGVOX (Bi 2 Mg x V 1Àx O 5.5À1.5xÀd ) ... more The impedance of the polycrystalline oxide ion conductor BIMGVOX (Bi 2 Mg x V 1Àx O 5.5À1.5xÀd ) for composition x = 0.13 was measured in the frequency range from 10 MHz to 0.01 Hz at temperatures between 20 -C and 680 -C using an automated set-up which allowed measurements of high impedance. Impedance spectra were analysed by non-linear least squares fitting of equivalent circuit, which models grain interiors conductivity with charge carrier relaxation represented by the Cole -Cole function, grain boundaries resistance with parallel non-ideal capacitance, and impedance of platinum electrodes. Determination of electrical properties of the polycrystalline sample was possible up to about 300 -C. At higher temperature, electrode impedance dominated the impedance spectrum and only the total ionic conductivity of the sample could be estimated. Temperature dependence of the intragrain conductivity and charge carrier relaxation was studied as well as of the macroscopic grain boundary conductance and capacitance.

Solid State Ionics, 2005

A combination of variable temperature X-ray powder diffraction, ac impedance spectroscopy and dif... more A combination of variable temperature X-ray powder diffraction, ac impedance spectroscopy and differential thermal analysis (DTA) has been used to characterise phase transitions in the Bi2ZrxV1−xO5.5−(x/2)−δ, BIMEVOX system. At low substitution levels α-, β-, and γ-phase BIMEVOX structures are observed as a function of temperature with some evidence for an intermediate phase, ɛ, seen between β and γ phases on

Materials Science Forum, 2004

Key Engineering Materials, 1991

Solid State Phenomena, 1994

Solid State Phenomena, 1994

ECS Transactions, 2007

ABSTRACT

Physica Status Solidi (a), 2003

Phase transitions in BIMGVOX, Bi2MgxV1−xO5.5−3x/2−δ, have been studied using a combination of a.c... more Phase transitions in BIMGVOX, Bi2MgxV1−xO5.5−3x/2−δ, have been studied using a combination of a.c. impedance spectroscopy, differential thermal analysis and variable temperature X-ray powder diffraction. Two composition regions were examined. In the first, below x = 0.10, phase transitions associated with the α, β and γ-phases are observed. In the second region above x = 0.10 the γ′ ⟷ γ transition is clearly observable. Trends in the refined unit cell parameters were particularly indicative of the phase transitions. The results are compared to those obtained for parent compound Bi4V2O11−δ.

Solid State Ionics, 2011

Electrolytes based on star-branched poly(ethylene oxide) with lithium bis(trifluoromethanesulfone... more Electrolytes based on star-branched poly(ethylene oxide) with lithium bis(trifluoromethanesulfone)imide LiTFSI and lithium iodide salts were prepared by casting from solution. The electrical properties of electrolytes subjected to various heating and cooling runs were studied by impedance spectroscopy and impedance spectroscopy simultaneous with optical microscope observation. Differential scanning calorimetry was used for additional characterization. The results indicate that in electrolytes with high content of salt, values of ionic conductivity comparable to that of dilute electrolytes can be achieved. Moreover, electrolytes with high amount of salt seem to show weaker temperature dependence of conductivity. Promising results in terms of ionic conductivity were obtained for mixture of LiTFSI and lithium iodide. A few problems which may decrease the performance of studied system as a solid electrolyte were also identified, from which changes of physical properties of samples subjected to thermal cycles and aging seem to be the most important ones.

Solid State Ionics, 2011

... 11], [12], [13] and [14]. The study of this system dates back to 1938, with the description o... more ... 11], [12], [13] and [14]. The study of this system dates back to 1938, with the description of the mineral russellite (Bi 2 WO 6 ) [15], the structure of which was later shown to be that of an n = 1 Aurivillius phase [16]. A review of the ...

Solid State Ionics, 2008

A detailed investigation using X-ray and neutron powder diffraction as well as ac impedance spect... more A detailed investigation using X-ray and neutron powder diffraction as well as ac impedance spectroscopy in the substituted bismuth oxide system Bi7Nb2 − 2xY2xO15.5 − 2x is presented. Combined refinement of variable temperature X-ray and neutron powder diffraction data reveal both compositional and temperature dependencies of the oxide ion distribution in this system. Oxide ions are found to be distributed over three crystallographically distinct sites, with one site exclusively associated with the dopant cations Nb5+ and Y3+ leading to a distorted octahedral geometry for these ions. Changes in the oxide ion distribution are correlated with a non-linear thermal expansion as well as non-Arrhenius behaviour of total conductivity at high temperatures.

Ionics, 2010

Li1.3Al0.15Y0.15Ti1.7(PO4)3 compound was synthesized by solid-state reaction, and ceramics were s... more Li1.3Al0.15Y0.15Ti1.7(PO4)3 compound was synthesized by solid-state reaction, and ceramics were sintered. The surfaces of the ceramics were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. Li1.3Al0.15Y0.15Ti1.7(PO4)3 samples were tested in solid galvanic cells Ag|O2+CO2|Li2CO3|Li1.3Al0.15Y0.15Ti1.7(PO4)3|LiMnO2+Mn2O3|O2|Ag. The electromotive force measurements of this cell indicated that investigated samples are practically pure Li-ion conductors. Impedance spectroscopy studies have been performed in the frequency range 10−2–3·109 Hz and temperatures from −57 °C to 334 °C. Three dispersion regions related to Li+ ionic transport in bulk, grain boundaries of the ceramics and to polarization of electrodes have been found. Total conductivity changes according to Arrhenius law in the studied temperature range, but an anomalous behavior was observed for the bulk conductivity of the ceramics.

Simultaneous impedance measurements and optical observations of polymer electrolytes were conduct... more 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(CF 3 SO 2 ) 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.

Journal of Physics-condensed Matter, 2012

A study of phase and electrical behaviour in the bismuth niobate, Bi(4)NbO(8.5), using x-ray and ... more A study of phase and electrical behaviour in the bismuth niobate, Bi(4)NbO(8.5), using x-ray and neutron powder diffraction, thermogravimetric analysis (TGA), x-ray photoelectron spectroscopy (XPS) and ac impedance spectroscopy is presented. Two polymorphs were identified in this composition, a tetragonal phase (type III), which can appear at temperatures above 800 °C and a pseudo-cubic phase (type II) evident at lower temperatures. The defect structure analysis of the type II phase is consistent with the existence of chains of niobate polyhedra, which facilitate electronic conduction at low temperatures. The appearance of the type III phase is strongly dependent on experimental conditions and TGA and XPS measurements suggest a likely association with change in oxygen stoichiometry.

Journal of Physics and Chemistry of Solids, 2008

Li1+xMn2-xO4Li1+xMn2-xO4 spinels have been prepared by wet route technique in the whole concentra... more Li1+xMn2-xO4Li1+xMn2-xO4 spinels have been prepared by wet route technique in the whole concentration range 0⩽x⩽13. Structural analysis has been performed by X-ray diffraction and scanning electron microscopy and Raman spectroscopy. The investigation of impurity phases by magnetic experiments complete the sample characterization, allowing for a comparison with samples obtained by other chemical routes. The analysis of the intrinsic magnetic properties show that the magnetic interactions are Mn3+–O–Mn3+Mn3+–O–Mn3+ interactions in a geometrically frustrated lattice, while the Mn4+Mn4+–Mn4+Mn4+ interactions are negligible, with the consequence that the paramagnetic Curie temperature vanishes in the limit x≃13 where only Mn4+Mn4+ ions remain. A consistent description of both the extrinsic and the intrinsic properties including former investigations of electron paramagnetic resonance has been achieved in relation to the electrochemical properties.

Solid State Ionics, 2005

Electrical conductivity and dielectric properties of lithium manganese spinels, Li1+dMn2−dO4, d=0... more Electrical conductivity and dielectric properties of lithium manganese spinels, Li1+dMn2−dO4, d=0 and d=0.005, obtained by sol–gel method, were studied by impedance spectroscopy. Parameters of relaxation function were obtained by fitting model response to the measured impedance. As evidenced by the X-ray powder diffraction, samples heat-treated at 800 °C undergo upon cooling a phase transition from cubic to an orthorhombic structure

Superionic Conductor Physics - Proceedings of the 1st International Discussion Meeting on Superionic Conductor Physics, 2007

Materials for Lithium-Ion Batteries, 2000

Solid State Ionics, 2005

The impedance of the polycrystalline oxide ion conductor BIMGVOX (Bi 2 Mg x V 1Àx O 5.5À1.5xÀd ) ... more The impedance of the polycrystalline oxide ion conductor BIMGVOX (Bi 2 Mg x V 1Àx O 5.5À1.5xÀd ) for composition x = 0.13 was measured in the frequency range from 10 MHz to 0.01 Hz at temperatures between 20 -C and 680 -C using an automated set-up which allowed measurements of high impedance. Impedance spectra were analysed by non-linear least squares fitting of equivalent circuit, which models grain interiors conductivity with charge carrier relaxation represented by the Cole -Cole function, grain boundaries resistance with parallel non-ideal capacitance, and impedance of platinum electrodes. Determination of electrical properties of the polycrystalline sample was possible up to about 300 -C. At higher temperature, electrode impedance dominated the impedance spectrum and only the total ionic conductivity of the sample could be estimated. Temperature dependence of the intragrain conductivity and charge carrier relaxation was studied as well as of the macroscopic grain boundary conductance and capacitance.

Solid State Ionics, 2005

A combination of variable temperature X-ray powder diffraction, ac impedance spectroscopy and dif... more A combination of variable temperature X-ray powder diffraction, ac impedance spectroscopy and differential thermal analysis (DTA) has been used to characterise phase transitions in the Bi2ZrxV1−xO5.5−(x/2)−δ, BIMEVOX system. At low substitution levels α-, β-, and γ-phase BIMEVOX structures are observed as a function of temperature with some evidence for an intermediate phase, ɛ, seen between β and γ phases on

Materials Science Forum, 2004

Key Engineering Materials, 1991

Solid State Phenomena, 1994

Solid State Phenomena, 1994

ECS Transactions, 2007

ABSTRACT

Physica Status Solidi (a), 2003

Phase transitions in BIMGVOX, Bi2MgxV1−xO5.5−3x/2−δ, have been studied using a combination of a.c... more Phase transitions in BIMGVOX, Bi2MgxV1−xO5.5−3x/2−δ, have been studied using a combination of a.c. impedance spectroscopy, differential thermal analysis and variable temperature X-ray powder diffraction. Two composition regions were examined. In the first, below x = 0.10, phase transitions associated with the α, β and γ-phases are observed. In the second region above x = 0.10 the γ′ ⟷ γ transition is clearly observable. Trends in the refined unit cell parameters were particularly indicative of the phase transitions. The results are compared to those obtained for parent compound Bi4V2O11−δ.

Solid State Ionics, 2011

Electrolytes based on star-branched poly(ethylene oxide) with lithium bis(trifluoromethanesulfone... more Electrolytes based on star-branched poly(ethylene oxide) with lithium bis(trifluoromethanesulfone)imide LiTFSI and lithium iodide salts were prepared by casting from solution. The electrical properties of electrolytes subjected to various heating and cooling runs were studied by impedance spectroscopy and impedance spectroscopy simultaneous with optical microscope observation. Differential scanning calorimetry was used for additional characterization. The results indicate that in electrolytes with high content of salt, values of ionic conductivity comparable to that of dilute electrolytes can be achieved. Moreover, electrolytes with high amount of salt seem to show weaker temperature dependence of conductivity. Promising results in terms of ionic conductivity were obtained for mixture of LiTFSI and lithium iodide. A few problems which may decrease the performance of studied system as a solid electrolyte were also identified, from which changes of physical properties of samples subjected to thermal cycles and aging seem to be the most important ones.

Solid State Ionics, 2011

... 11], [12], [13] and [14]. The study of this system dates back to 1938, with the description o... more ... 11], [12], [13] and [14]. The study of this system dates back to 1938, with the description of the mineral russellite (Bi 2 WO 6 ) [15], the structure of which was later shown to be that of an n = 1 Aurivillius phase [16]. A review of the ...

Solid State Ionics, 2008

A detailed investigation using X-ray and neutron powder diffraction as well as ac impedance spect... more A detailed investigation using X-ray and neutron powder diffraction as well as ac impedance spectroscopy in the substituted bismuth oxide system Bi7Nb2 − 2xY2xO15.5 − 2x is presented. Combined refinement of variable temperature X-ray and neutron powder diffraction data reveal both compositional and temperature dependencies of the oxide ion distribution in this system. Oxide ions are found to be distributed over three crystallographically distinct sites, with one site exclusively associated with the dopant cations Nb5+ and Y3+ leading to a distorted octahedral geometry for these ions. Changes in the oxide ion distribution are correlated with a non-linear thermal expansion as well as non-Arrhenius behaviour of total conductivity at high temperatures.

Ionics, 2010

Li1.3Al0.15Y0.15Ti1.7(PO4)3 compound was synthesized by solid-state reaction, and ceramics were s... more Li1.3Al0.15Y0.15Ti1.7(PO4)3 compound was synthesized by solid-state reaction, and ceramics were sintered. The surfaces of the ceramics were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. Li1.3Al0.15Y0.15Ti1.7(PO4)3 samples were tested in solid galvanic cells Ag|O2+CO2|Li2CO3|Li1.3Al0.15Y0.15Ti1.7(PO4)3|LiMnO2+Mn2O3|O2|Ag. The electromotive force measurements of this cell indicated that investigated samples are practically pure Li-ion conductors. Impedance spectroscopy studies have been performed in the frequency range 10−2–3·109 Hz and temperatures from −57 °C to 334 °C. Three dispersion regions related to Li+ ionic transport in bulk, grain boundaries of the ceramics and to polarization of electrodes have been found. Total conductivity changes according to Arrhenius law in the studied temperature range, but an anomalous behavior was observed for the bulk conductivity of the ceramics.

Simultaneous impedance measurements and optical observations of polymer electrolytes were conduct... more 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(CF 3 SO 2 ) 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.

Journal of Physics-condensed Matter, 2012

A study of phase and electrical behaviour in the bismuth niobate, Bi(4)NbO(8.5), using x-ray and ... more A study of phase and electrical behaviour in the bismuth niobate, Bi(4)NbO(8.5), using x-ray and neutron powder diffraction, thermogravimetric analysis (TGA), x-ray photoelectron spectroscopy (XPS) and ac impedance spectroscopy is presented. Two polymorphs were identified in this composition, a tetragonal phase (type III), which can appear at temperatures above 800 °C and a pseudo-cubic phase (type II) evident at lower temperatures. The defect structure analysis of the type II phase is consistent with the existence of chains of niobate polyhedra, which facilitate electronic conduction at low temperatures. The appearance of the type III phase is strongly dependent on experimental conditions and TGA and XPS measurements suggest a likely association with change in oxygen stoichiometry.

Journal of Physics and Chemistry of Solids, 2008

Li1+xMn2-xO4Li1+xMn2-xO4 spinels have been prepared by wet route technique in the whole concentra... more Li1+xMn2-xO4Li1+xMn2-xO4 spinels have been prepared by wet route technique in the whole concentration range 0⩽x⩽13. Structural analysis has been performed by X-ray diffraction and scanning electron microscopy and Raman spectroscopy. The investigation of impurity phases by magnetic experiments complete the sample characterization, allowing for a comparison with samples obtained by other chemical routes. The analysis of the intrinsic magnetic properties show that the magnetic interactions are Mn3+–O–Mn3+Mn3+–O–Mn3+ interactions in a geometrically frustrated lattice, while the Mn4+Mn4+–Mn4+Mn4+ interactions are negligible, with the consequence that the paramagnetic Curie temperature vanishes in the limit x≃13 where only Mn4+Mn4+ ions remain. A consistent description of both the extrinsic and the intrinsic properties including former investigations of electron paramagnetic resonance has been achieved in relation to the electrochemical properties.

Solid State Ionics, 2005

Electrical conductivity and dielectric properties of lithium manganese spinels, Li1+dMn2−dO4, d=0... more Electrical conductivity and dielectric properties of lithium manganese spinels, Li1+dMn2−dO4, d=0 and d=0.005, obtained by sol–gel method, were studied by impedance spectroscopy. Parameters of relaxation function were obtained by fitting model response to the measured impedance. As evidenced by the X-ray powder diffraction, samples heat-treated at 800 °C undergo upon cooling a phase transition from cubic to an orthorhombic structure