W. Sadowski - Academia.edu (original) (raw)
Papers by W. Sadowski
Acta Physica Polonica A, 2008
Granular metals and superconductors are very interesting materials thanks to their untypical elec... more Granular metals and superconductors are very interesting materials thanks to their untypical electrical properties caused by the presence of the Coulomb effects, electron and Cooper pair tunnelling and various aspects of disorder. Most typical and widely studied representatives of this group consist of low T c superconductor granules distributed in insulating matrix (e.g. lead in germanium matrix). In comparison with them a system of granules of high-T c superconductors embedded in an insulating matrix is more difficult to be experimentally realised. (Bi,Pb)-Sr-Ca-Cu-O materials obtained with solid state crystallisation method may be considered as an example of granular and disordered metals and superconductors. Solid state crystallisation of initially amorphous material leads to formation of 2201 and 2212 granules embedded in the insulating or semiconducting matrix. Further annealing causes increase in size and/or the number of conducting grains and decrease in the width of the insulating barriers between them. In both cases of low-and high-T c granular materials the main parameters, which determine their properties, are the amount of metallic phases and the tunnelling conductivity between the neighbouring grains. In this work some properties of low-and high-T c granular materials are discussed and compared.
Solid State Communications, 1990
ABSTRACT
Radiation Effects and Defects in Solids, 2003
ABSTRACT
Physica C: Superconductivity, 2000
Phases Bi2Sr2CaCu2Ox (2212) and Bi2Sr2Ca2Cu3Ox (2223) were grown by a crystallization of the BiS... more Phases Bi2Sr2CaCu2Ox (2212) and Bi2Sr2Ca2Cu3Ox (2223) were grown by a crystallization of the BiSrCaCuO glass. The crystallisation was carried out between 820°C and 879°C. Both normal and superconducting properties were influenced by the conditions of crystallisation. Very short annealing time was sufficient to obtain superconducting phases. Appearance of 2223 phase as a result of only a few minutes' annealing been observed.
Physica C: Superconductivity, 1994
ABSTRACT
Physical Review B, 1996
High-temperature positron two-dimensional angular correlation of annihilation radiation ͑2D-ACAR͒... more High-temperature positron two-dimensional angular correlation of annihilation radiation ͑2D-ACAR͒ measurements have recently been succesfully applied to map parts of the Fermi surface of YBa 2 Cu 3 O 7Ϫ␦. Using the same principle, we have been able to observe with a bulk sensitive method, the Fermi surface of Nd 2Ϫx Ce x CuO 4Ϫ␦. Although positron trapping by defects and correlation effects are strong, positron 2D-ACAR measurements provide a signal from the Fermi surface which agrees with band-structure calculations, confirming earlier surface sensitive photoemission experiments.
Journal of the Less Common Metals, 1990
Physica C: Superconductivity, 1991
ABSTRACT
Physica C: Superconductivity, 1994
It is found that the frequency dependence R(f) of the resistance of HTS samples at T< Tc i... more It is found that the frequency dependence R(f) of the resistance of HTS samples at T< Tc is nonmonotomic in the range 0 - 108 Hz. It is also found that the dc magnetic field produces different influence on different parts of the R(f) dependence.
Journal of Applied Physics, 1990
X-ray photoelectron spectroscopy was used to examine vapor deposited Ag overlayers on YBa2Cu3O7−x... more X-ray photoelectron spectroscopy was used to examine vapor deposited Ag overlayers on YBa2Cu3O7−x thin films and cleaved single-crystal surfaces (x=1), including the effects of subsequent heat treatment in oxygen. The core level spectra of the present tetragonal crystals were found to closely resemble those previously reported for nominally orthorhombic superconducting samples. Minor differences, notably an increased fraction of Cu in
Europhysics Letters (EPL), 1992
Using a forced torsion pendulum we have investigated the frequency, amplitude and orientation dep... more Using a forced torsion pendulum we have investigated the frequency, amplitude and orientation dependence of the vortex response in untwinned single crystals of YBa2Cu3O7−δ. A new thermally activated dissipation peak which appears at high amplitude, accompanied by a crossover in the pinning, has been observed in addition to the one associated to the controversial vortex melting. The shape and mass
Crystal Research and Technology, 2001
Crystal growth of Ca-doped PrBa 2 Cu 3 O 7-δ (Pr-123) single crystals by slow cooling of Pr 3 O 1... more Crystal growth of Ca-doped PrBa 2 Cu 3 O 7-δ (Pr-123) single crystals by slow cooling of Pr 3 O 11 -CaCO 3 -BaCO 3 -CuO melts (self-flux technique) in ambient air atmosphere was studied. As the first approach the growth of Ca-free crystals in Al 2 O 3 and ZrO 2 crucibles was investigated. The best quality crystals with the average size of 5 x 5 x 0.2mm 3 were obtained from Al 2 O 3 crucibles for Ba/Cu = 0.41 and 15 wt.% (2.41 mol.%) of stoichiometric Pr-123 solute in the melt. Next, using CaCO 3 as calcium source (0.09 -12.68 wt.%), the good quality Pr 1-x Ca x Ba 2 Cu 3 O 7-δ crystals with 0 ≤ x ≤ 0.26 were grown in the Al 2 O 3 crucibles from the solution with fixed value of Ba/Cu = 0.41. The oxygenated single crystals with size up to 5 x 8 x 0.2 mm 3 were used for electric transport investigations from four-probe resistivity measurements. The temperature dependence of resistivity of Ca-doped Pr-123 crystals is typical for systems with locallized states and, in principle, follows the Mott law for variable-range hopping (VRH).
Physica C: Superconductivity, 2000
Phases Bi2Sr2CaCu2Ox (2212) and Bi2Sr2Ca2Cu3Ox (2223) were grown by a crystallization of the BiS... more Phases Bi2Sr2CaCu2Ox (2212) and Bi2Sr2Ca2Cu3Ox (2223) were grown by a crystallization of the BiSrCaCuO glass. The crystallisation was carried out between 820°C and 879°C. Both normal and superconducting properties were influenced by the conditions of crystallisation. Very short annealing time was sufficient to obtain superconducting phases. Appearance of 2223 phase as a result of only a few minutes' annealing been observed.
Acta Physica Polonica A, 2008
Granular metals and superconductors are very interesting materials thanks to their untypical elec... more Granular metals and superconductors are very interesting materials thanks to their untypical electrical properties caused by the presence of the Coulomb effects, electron and Cooper pair tunnelling and various aspects of disorder. Most typical and widely studied representatives of this group consist of low T c superconductor granules distributed in insulating matrix (e.g. lead in germanium matrix). In comparison with them a system of granules of high-T c superconductors embedded in an insulating matrix is more difficult to be experimentally realised. (Bi,Pb)-Sr-Ca-Cu-O materials obtained with solid state crystallisation method may be considered as an example of granular and disordered metals and superconductors. Solid state crystallisation of initially amorphous material leads to formation of 2201 and 2212 granules embedded in the insulating or semiconducting matrix. Further annealing causes increase in size and/or the number of conducting grains and decrease in the width of the insulating barriers between them. In both cases of low-and high-T c granular materials the main parameters, which determine their properties, are the amount of metallic phases and the tunnelling conductivity between the neighbouring grains. In this work some properties of low-and high-T c granular materials are discussed and compared.
Solid State Communications, 1990
ABSTRACT
Radiation Effects and Defects in Solids, 2003
ABSTRACT
Physica C: Superconductivity, 2000
Phases Bi2Sr2CaCu2Ox (2212) and Bi2Sr2Ca2Cu3Ox (2223) were grown by a crystallization of the BiS... more Phases Bi2Sr2CaCu2Ox (2212) and Bi2Sr2Ca2Cu3Ox (2223) were grown by a crystallization of the BiSrCaCuO glass. The crystallisation was carried out between 820°C and 879°C. Both normal and superconducting properties were influenced by the conditions of crystallisation. Very short annealing time was sufficient to obtain superconducting phases. Appearance of 2223 phase as a result of only a few minutes' annealing been observed.
Physica C: Superconductivity, 1994
ABSTRACT
Physical Review B, 1996
High-temperature positron two-dimensional angular correlation of annihilation radiation ͑2D-ACAR͒... more High-temperature positron two-dimensional angular correlation of annihilation radiation ͑2D-ACAR͒ measurements have recently been succesfully applied to map parts of the Fermi surface of YBa 2 Cu 3 O 7Ϫ␦. Using the same principle, we have been able to observe with a bulk sensitive method, the Fermi surface of Nd 2Ϫx Ce x CuO 4Ϫ␦. Although positron trapping by defects and correlation effects are strong, positron 2D-ACAR measurements provide a signal from the Fermi surface which agrees with band-structure calculations, confirming earlier surface sensitive photoemission experiments.
Journal of the Less Common Metals, 1990
Physica C: Superconductivity, 1991
ABSTRACT
Physica C: Superconductivity, 1994
It is found that the frequency dependence R(f) of the resistance of HTS samples at T< Tc i... more It is found that the frequency dependence R(f) of the resistance of HTS samples at T< Tc is nonmonotomic in the range 0 - 108 Hz. It is also found that the dc magnetic field produces different influence on different parts of the R(f) dependence.
Journal of Applied Physics, 1990
X-ray photoelectron spectroscopy was used to examine vapor deposited Ag overlayers on YBa2Cu3O7−x... more X-ray photoelectron spectroscopy was used to examine vapor deposited Ag overlayers on YBa2Cu3O7−x thin films and cleaved single-crystal surfaces (x=1), including the effects of subsequent heat treatment in oxygen. The core level spectra of the present tetragonal crystals were found to closely resemble those previously reported for nominally orthorhombic superconducting samples. Minor differences, notably an increased fraction of Cu in
Europhysics Letters (EPL), 1992
Using a forced torsion pendulum we have investigated the frequency, amplitude and orientation dep... more Using a forced torsion pendulum we have investigated the frequency, amplitude and orientation dependence of the vortex response in untwinned single crystals of YBa2Cu3O7−δ. A new thermally activated dissipation peak which appears at high amplitude, accompanied by a crossover in the pinning, has been observed in addition to the one associated to the controversial vortex melting. The shape and mass
Crystal Research and Technology, 2001
Crystal growth of Ca-doped PrBa 2 Cu 3 O 7-δ (Pr-123) single crystals by slow cooling of Pr 3 O 1... more Crystal growth of Ca-doped PrBa 2 Cu 3 O 7-δ (Pr-123) single crystals by slow cooling of Pr 3 O 11 -CaCO 3 -BaCO 3 -CuO melts (self-flux technique) in ambient air atmosphere was studied. As the first approach the growth of Ca-free crystals in Al 2 O 3 and ZrO 2 crucibles was investigated. The best quality crystals with the average size of 5 x 5 x 0.2mm 3 were obtained from Al 2 O 3 crucibles for Ba/Cu = 0.41 and 15 wt.% (2.41 mol.%) of stoichiometric Pr-123 solute in the melt. Next, using CaCO 3 as calcium source (0.09 -12.68 wt.%), the good quality Pr 1-x Ca x Ba 2 Cu 3 O 7-δ crystals with 0 ≤ x ≤ 0.26 were grown in the Al 2 O 3 crucibles from the solution with fixed value of Ba/Cu = 0.41. The oxygenated single crystals with size up to 5 x 8 x 0.2 mm 3 were used for electric transport investigations from four-probe resistivity measurements. The temperature dependence of resistivity of Ca-doped Pr-123 crystals is typical for systems with locallized states and, in principle, follows the Mott law for variable-range hopping (VRH).
Physica C: Superconductivity, 2000
Phases Bi2Sr2CaCu2Ox (2212) and Bi2Sr2Ca2Cu3Ox (2223) were grown by a crystallization of the BiS... more Phases Bi2Sr2CaCu2Ox (2212) and Bi2Sr2Ca2Cu3Ox (2223) were grown by a crystallization of the BiSrCaCuO glass. The crystallisation was carried out between 820°C and 879°C. Both normal and superconducting properties were influenced by the conditions of crystallisation. Very short annealing time was sufficient to obtain superconducting phases. Appearance of 2223 phase as a result of only a few minutes' annealing been observed.