| 1. |
|
|
| 2. |
- Nygren, Mats, et al.
(författare)
-
The effect of Mg doping on the thermoelectric performance of Zn4Sb3 : International Conference on Thermoelectrics
- 2008
-
Ingår i: Institute of Electrical and Electronics Engineers. - 1094-2734. ; , s. 382-385
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of Mg doping of Zn4Sb3 on thermal and thermoelec. properties has been studied on 4 samples with a doping degree ranging from 0.1 to 2 at.% Mg, and compared to a pure, undoped sample. Lab. X-ray powder diffraction shows that all samples are pure single phase materials as further evidenced with higher confidence by Rietveld refinement of high resoln. synchrotron powder diffraction of the as synthesized 1 at.% and 2 at.% Mg doped samples. Zn4Sb3 undergoes a transition from the room temp. disordered phase to an ordered ' phase, going over an intermediate phase; differential scanning calorimetry show only small effects of doping on the phase transition temp. Phys. properties have been evaluated from 2-400 K for all samples. Some phys. property parameters are affected by doping, but no immediate improvement of ZT was achieved by the doping procedure. The reason for this is discussed in relation to differences in sample compaction.
|
|
| 3. |
- Nyström, Per, et al.
(författare)
-
The declining spadefoot toad Pelobates fuscus: calling site choice and conservation
- 2002
-
Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 25:4, s. 488-498
-
Tidskriftsartikel (refereegranskat)abstract
- We investigated whether local biotic and abiotic conditions could explain the occurrence of calling males of the declining spadefoot toad Pelobates fuscus in 72 ponds in southern Sweden. The ponds covered the entire distribution range of P. fuscus and were monitored during the breeding season in 2000. Calling males were found in 33 ponds. representing ca 50% of all known ponds for the species ill Sweden. They had a non-random distribution and a discriminant analysis including 19 environmental variables successfully classified 86% of the ponds as with or without calling males A stepwise discriminant analysis selected eight of these variables and classified 85% of the ponds correctly. ponds with calling males were classified mainly on characteristics of the ponds, whereas composition of the terrestrial habitat close to the ponds and traffic load within 500 in had little influence on the distribution of calling males. Ponds with P. fuscus were large, permanent and eutrophic with high concentrations of oxygen and high spring temperatures. They also had a high proportion of shoreline with steep banks. Permanent ponds with calling males typically had a low abundance of predatory fish and crayfish: only two of the ponds with P. fuscus contained predatory fish. The results of this study indicate that interactions between physical factors (e.g. pond drying) and predation determine the presence of P. fuscus. Because P. fuscus has specific habitat requirements necessary for its survival and high site fidelity, it is particularly vulnerable to local changes in the condition of its natural breeding ponds. The situation is particularly serious for this species because the majority of the ponds that are within its dispersal range do not seem to be suitable for P. fuscus because of physical constraints.
|
|
| 4. |
- Pedersen, Birgitte L., et al.
(författare)
-
Substitution in MxZn4-xSb3 : Effect on Thermal Stability, Crystal Structure, Phase Transitions, and Thermoelectric Performance
- 2010
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 22:7, s. 2375-2383
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of Cd substitution in MxZn4−xSb3 on the high-temperature thermal stability, low-temperature phase transitions and thermoelectric properties have been studied on three samples with a substitution degree of 0.1, 1, and 2 at % Cd (x = 0.004, 0.04, 0.08). The high-temperature thermal stability in atmospheric air of a 1% substituted sample is compared with an unsubstituted Zn4Sb3 sample. Multitemperature synchrotron powder diffraction data reveals that while only ∼42 wt % of the original Zn4Sb3 phase remains in the unsubstituted sample after three heating cycles to 625 K, 78 wt % is preserved in the Cd-substituted sample. Thus, Cd-substitution provides a significant improvement of the thermal stability of Zn4Sb3. Multitemperature synchrotron powder diffraction data measured between 90 and 300 K reveal that Cd substitution has a suppressing effect on the α′−α−β phase transitions. With increasing substitution, there is also a significant change in the individual Zn site occupancies. Differential scanning calorimetry shows an apparent correlation between Cd content and phase transition temperature. Thermoelectric properties have been measured from 2 to 400 K for all samples, and although some physical properties are significantly affected by doping, no immediate improvement of ZT was achieved.
|
|
| 5. |
- Pedersen, Birgitte L., et al.
(författare)
-
The effect of Mg doping on the thermoelectric performance of Zn4Sb3
- 2009
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 105:1, s. 13517-
-
Tidskriftsartikel (refereegranskat)abstract
- Cation doping studies of high performance thermoelectric (ZnSb3)-Sb-4 have so far focused on elements with larger electronegativity than Zn. Mg has a lower electronegativity than Zn, and, in the present paper, the effect of Mg doping of Zn4Sb3 on phase transition temperatures and thermal and thermoelectric properties have been studied on five samples with a doping degree ranging from 0.1 to 2 at. % Mg. The results are compared with data obtained for a pure, undoped sample. Laboratory x-ray powder diffraction shows that all samples are single phase materials as further evidenced with higher confidence by Rietveld refinement of high resolution synchrotron powder diffraction of as synthesized 1 and 2 at. % Mg doped samples. Multitemperature synchrotron powder diffraction and differential scanning calorimetry reveal a significant effect of Mg-doping on the low temperature phase transitions in one sample (0.5 at. % Mg), whereas the other samples showed only small or no effect. Physical properties have been evaluated from 2-400 K for all samples. Some physical property parameters are affected by doping but no immediate improvement of ZT was achieved. The reason for this is discussed in relation to differences in sample compaction.
|
|
