1. |
- Pedersen, K, et al.
(författare)
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Texture and microstructure of Cr2O3 and (Cr,Al)2O3 thin films deposited by reactive inductively coupled plasma magnetron sputtering
- 2010
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Ingår i: THIN SOLID FILMS. - : Elsevier Science B.V., Amsterdam.. - 0040-6090. ; 518:15, s. 4294-4298
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Tidskriftsartikel (refereegranskat)abstract
- Cr2O3 and (Cr,Al)(2)O-3 films were grown using reactive dc and inductively coupled plasma magnetron sputtering at substrate temperatures of 300-450 degrees C. For pure chromia, alpha-Cr2O3 films with fiber texture were grown; the out-of-plane texture could be controlled from andlt; 0001 andgt; to andlt;10andlt;(1)over barandgt;4andgt;. The former texture was obtained as a consequence of competitive growth with no applied bias or inductively coupled plasma, while the latter was obtained at moderate bias ( - 50 V), probably due to recrystallization driven by ion-bombardment-induced strain. By reactive codeposition of Cr and Al, a corundum-structured metastable solid solution alpha-(Cr,Al)(2)O-3 with Cr/Al ratios of 2-10 was grown with a dense, fine-grained morphology. Hardness and reduced elastic modulus values were in the ranges 24-27 GPa and 190-230 GPa, respectively.
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2. |
- Sillassen, M., et al.
(författare)
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Ionic conductivity and thermal stability of magnetron-sputtered nanocrystalline yttria-stabilized zirconia
- 2009
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 105:10, s. 104907-
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Tidskriftsartikel (refereegranskat)abstract
- Thermally stable, stoichiometric, cubic yttria-stabilized zirconia (YSZ) thin-film electrolytes have been synthesized by reactive pulsed dc magnetron sputtering from a Zr-Y (80/20 at. %) alloy target. Films deposited at floating potential had a ‹111› texture. Single-line profile analysis of the 111 x-ray diffraction peak yielded a grain size of ~20 nm and a microstrain of ~2% regardless of deposition temperature. Films deposited at 400 °C and selected bias voltages in the range from -70 to -200 V showed a reduced grain size for higher bias voltages, yielding a grain size of ~6 nm and a microstrain of ~2.5% at bias voltages of -175 and -200 V with additional incorporation of argon. The films were thermally stable; very limited grain coarsening was observed up to an annealing temperature of 800 °C. Temperature-dependent impedance spectroscopy analysis of the YSZ films with Ag electrodes showed that the in-plane ionic conductivity was within one order of magnitude higher in films deposited with substrate bias corresponding to a decrease in grain size compared to films deposited at floating potential. This suggests that there is a significant contribution to the ionic conductivity from grain boundaries. The activation energy for oxygen ion migration was determined to be between 1.14 and 1.30 eV.
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3. |
- Sun, Y., et al.
(författare)
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Low-Cost High-Performance Zinc Antimonide Thin Films for Thermoelectric Applications
- 2012
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 24:13, s. 1693-1696
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Tidskriftsartikel (refereegranskat)abstract
- Zinc antimonide thin films with high thermoelectric performance are produced by a simple sputtering method. The phase-pure Zn4Sb3 and ZnSb thin films fulfill the key requirements for commercial TE power generation: cheap elements, cheap fabrication method, high performance and thermal stability. In addition, two completely new meta-stable crystalline phases of zinc antimonide have been discovered.
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4. |
- Sillassen, M, et al.
(författare)
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Concentration-dependent ionic conductivity and thermal stability of magnetron-sputtered nanocrystalline scandia-stabilized zirconia
- 2010
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Ingår i: SOLID STATE IONICS. - : Elsevier Science B.V., Amsterdam.. - 0167-2738. ; 181:23-24, s. 1140-1145
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Tidskriftsartikel (refereegranskat)abstract
- Nanocrystalline (nc) scandia-stabilized zirconia (SSZ) electrolytes with scandia contents of 5.9 to 15.9 mol% ere synthesized by reactive magnetron sputtering. For scandia content andgt;= 9.1 mol%, the as-deposited films were pure cubic phase with andlt; 111 andgt; texture, while traces of tetragonal phase was found for lower Sc content. Single-line profile analysis of the 111 X-ray diffraction peak yielded an out-of-plane grain size of similar to 10 nm and a microstrain of 2.0-2.2%, regardless of scandia content, for films deposited at 400 degrees C and a bias of -70 V. Films deposited at higher bias voltages showed a reduced grain size, yielding a grain size of similar to 6 nm and a microstrain of similar to 2.5% at -200 V and -250 V with additional incorporation of argon. Temperature-dependent impedance spectroscopy of the SSZ films showed that the in-plane ionic conductivity had a maximum close to 10.7 mol% and decreased almost an order of magnitude as the scandia - content was increased to 15.9 mol%. The activation energy for oxygen ion migration was determined to be between 130-1.43 eV. In addition, no dependence on grain size was observed. The above observations suggest a bulk mechanism for ionic conduction.
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5. |
- Sillassen, M, et al.
(författare)
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Effects of dopant concentration and impurities on the conductivity of magnetron-sputtered nanocrystalline yttria-stabilized zirconia
- 2010
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Ingår i: SOLID STATE IONICS. - : Elsevier Science B.V., Amsterdam.. - 0167-2738. ; 181:19-20, s. 864-867
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Tidskriftsartikel (refereegranskat)abstract
- Cubic yttria-stabilized zirconia (YSZ) films with yttria concentrations of 8.7, 9.9, and 11 mol% have been deposited by reactive pulsed DC magnetron from Zr-Y alloy targets. The overall microstructure and texture in the films showed no dependence on the yttria concentration. Films deposited at floating potential had a andlt; 111 andgt; texture. Single-line profile analysis of the 111 X-ray diffraction peak yielded a grain size of similar to 18 nm and a microstrain of similar to 2%. regardless of deposition temperature. Films deposited at 400 degrees C and selected bias voltages in the range from -70 V to -200 V showed a reduced grain size for higher bias voltages, yielding a grain size of similar to 7 nm and a microstrain of similar to 2.5% at a bias voltage of -200 V with additional incorporation of argon. Furthermore, the effect of impurities on the ionic conductivity has been investigated, since Hf impurities were found in the samples with yttria concentrations of 8.7, and 9.9 mol%. Temperature-dependent impedance spectroscopy of the YSZ films, deposited at 400 degrees C and floating potential, showed no variation of the in-plane ionic conductivity with yttria concentration. However, for films deposited at 400 degrees C and a bias -70 V. the in-plane ionic conductivity decreased systematically for samples with yttria concentrations of 8.7 and 9.9 mol% compared to the sample with 11 mol% yttria. This suggests that ionic conduction is not a purely bulk mechanism, but mainly related to the grain boundaries. The activation energy for oxygen ion migration was determined to be between 1.25 and 1.32 eV.
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6. |
- Su, R., et al.
(författare)
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How the Anatase-to-Rutile Ratio Influences the Photoreactivity of TiO2
- 2011
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:49, s. 24287-24292
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Tidskriftsartikel (refereegranskat)abstract
- In 1991, Bickley et al. proposed a synergetic effect between anatase and rutile in Degussa P25. Since then, there has been an intensive debate about the correctness of this proposal, the origin of the synergism, and the right polymorph composition. However, a comparison of pure titanium dioxide samples with various anatase-to-rutile ratios, but otherwise identical properties, is missing. In this paper, we report about a series of utterly pure, highly porous titanium dioxide films with identical grain sizes, surface areas, and crystallinity, but varying polymorph compositions. Photocatalytic oxidation of methylene blue was utilized to investigate the influence of the anatase-to-rutile ratio on the photoreactivity. We clearly observe the synergetic effect within a well-defined range of anatase-to-rutile ratios. A film with similar to 60% anatase and similar to 40% rutile exhibits optimal performance at a 50% improved activity compared with pure anatase.
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7. |
- Sun, Y, et al.
(författare)
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Thermoelectric transport properties of highly oriented FeSb2 thin films
- 2009
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Ingår i: JOURNAL OF APPLIED PHYSICS. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 106:3
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Tidskriftsartikel (refereegranskat)abstract
- Highly textured FeSb2 films were produced on quartz wafers by a sputtering method. Their resistivity and Seebeck coefficient (S) were measured and a maximum absolute value of S similar to 160 mu V K-1 at 50 K was obtained. Hall measurements were employed to study the charge carrier concentrations and Hall mobilities of the FeSb2 films. By comparing with the transport properties of FeSb2 single crystals and an extrinsically doped FeSb1.98Te0.02 single crystal, the thermoelectric properties of the FeSb2 films are demonstrated to be dominated by the intrinsic properties of FeSb2 at a high charge carrier concentration.
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