| 1. |
- Andersson, Magnus, et al.
(författare)
-
CA AND PR SUBSTITUTION IN Y-BASED AND SM-BASED 1-2-3 COMPOUNDS
- 1993
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 48:10, s. 7590-7597
-
Tidskriftsartikel (refereegranskat)abstract
- Substitution with equal amounts of Ca and Pr has been studied mainly in Y- and Sm-based 1:2:3 samples and with some results also for Nd-based samples. Structural and chemical analysis and measurements of the superconducting T(c) and the upper critical magnetic field were performed. It was found that Ca and Pr can be dissolved in the orthorhombic structure up to about 25 at. % each in both Y- and Sm-based samples while for larger concentrations, only Pr continued to enter into the 1:2:3 structure. The depression of T(c) with Ca-Pr doping was found to be linear in concentration in contrast to the accelerated decrease in samples doped with only Pr. The rate of depression of T(c) increased in the sequence Y-, Sm-, and Nd-based hosts. The results suggest that Ca-Pr doping isolates a characteristic Pr-impurity effect in 1:2:3 samples. The critical magnetic-field slopes of Y- and Sm-based samples were almost independent of Ca-Pr content in the cosolubility region while a strong decrease was observed for larger Pr content, similar to 1:2:3 samples doped with Pr only. These results suggest an almost-temperature-independent magnetic pair-breaking effect by Pr.
|
|
| 2. |
|
|
| 3. |
- Andersson, Magnus, et al.
(författare)
-
STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF Y1-2XCAXPRXBA2CU3O7-GAMMA
- 1992
-
Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 190:3, s. 255-260
-
Tidskriftsartikel (refereegranskat)abstract
- Samples of the nominal composition Y1-2xCaxPrxBa2Cu3O7-delta with 0 less-than-or-equal-to x less-than-or-equal-to 0.4 have been studied by X-ray diffraction techniques, chemical analyses, and measurements of the super conducting transition temperature and the upper critical magnetic field. For x less-than-or-equal-to 0.25, the results indicate that Ca and Pr can both replace Y in agreement with the nominal composition, while for x > 0.25 only Pr enters the orthorhombic unit cell. Compared to Pr substitution in 1:2:3 we observe small changes in the depression of T(c) and strong changes in the critical field slopes. These results suggest that if Pr has a magnetic pair-breaking effect, it is close to being temperature independent.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Skoglundh, Magnus, 1965, et al.
(författare)
-
Characterization and catalytic properties of perovskites with nominal compositions La1-xSrxAl1-2yCuyRuyO3
- 1994
-
Ingår i: Applied Catalysis B: Environmental. ; 3:4, s. 259-274
-
Tidskriftsartikel (refereegranskat)abstract
- Nine different metal oxide catalysts were prepared by impregnating alumina washcoats with water solutions containing La3+, Sr2+, Cu2+ and Ru3+ ions and calcining them at 900-degrees-C. The produced samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) studies combined with energy-dispersive spectroscopy (EDS) analysis, X-ray powder diffraction and specific surface area measurements. A perovskite phase of the nominal composition La1-xSrxAl1-2yCuRuyO3 was found in all samples, in increasing amount in the samples with increasing contents of strontium and ruthenium. The catalysts were evaluated with respect to light-off temperatures and redox characteristics using two gas mixtures, one containing NO/CO/C3H6/O2/N2 and the other NO/CO/N2. The light-off temperatures for nitric oxide reduction decreased from 534 to 333-degrees-C for the catalysts without and with strontium and ruthenium, respectively. In the presence of oxygen the conversion of nitric oxide declined rapidly under oxidative conditions whereas in absence of oxygen this decline was less pronounced and found to be linear over the entire redox interval studied. These studies suggest that the perovskite phase takes an active part in the conversion of nitric oxide and carbon monoxide to nitrogen and carbon dioxide.
|
|
| 7. |
|
|
