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- Fors, Rickard, et al.
(författare)
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Comparison of Sol-Gel Derived and Pulsed Laser Deposited Epitaxial La0.67Ca0.33MnO3 Films for IR Bolometer
- 2004
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Ingår i: Mat. Res. Soc. Symp. Proc.. - : Springer Science and Business Media LLC. ; 811, s. E2.5.1-E2.5.6, s. 379-384
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial La0.67Ca0.33MnO3 films have been prepared on LaA1O3 crystals by pulsed laser deposition (PLD) and by a novel all-alkoxide sol-gel technique. Different out-of-plane lattice parameters are found for the as-prepared films, and scanning electron microscopy shows a more porous structure for sol-gel films as compared to PLD films. These differences are largely removed by post-annealing at 1000 °C. Transport measurements show maximum temperature coefficient of resistivity of 8.2 % K-1 at 258 K (PLD) and 6.1 % K-1 at 241 K (sol-gel) and :colossal magnetoresistance at 7 kOe of 35 % at 263 K (PLD) and 32 % at 246 K (sol-gel).
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- Pohl, Annika, et al.
(författare)
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Body mass index influences plasma concentration of neuropeptide Y in healthy female volunteers : A pilot study
- 2003
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Ingår i: Gynecological Endocrinology. - : Informa UK Limited. - 0951-3590 .- 1473-0766. ; 17:5, s. 409-412
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Tidskriftsartikel (refereegranskat)abstract
- Neuropeptide Y (NPY) was measured in plasma obtained from healthy female volunteers twice in the natural menstrual cycle or the hormonal cycle caused by oral contraceptives about 2 weeks apart. The ratio between the NPY plasma concentration in the second sample and the first sample was influenced negatively by body mass index (BMI). There were no differences in NPY plasma concentrations on comparing the first and second samples. Age and the use or non-use of oral contraceptives did not exert any influence. BMI might be a confounding factor when determining NPY in the plasma of healthy women.
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| 10. |
- Pohl, Annika, 1972-
(författare)
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Sol−Gel Synthesis of CMR Manganites
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of more advanced materials forms the basis of technological progress. One group of fascinating compounds with many potential applications in spintronic devices are the mixed-valence perovskite manganites. These have attracted considerable interest during the last decade through their very large magnetoresistance near the Curie Temperature. Although the properties of a material determinie any application, the development of reliable and flexible synthesis methods is crucial, as is the understanding of these methods. Knowledge of how different materials are formed is also of general importance in tailoring new materials. The aim of this project has therefore been not only to develop a new synthesis route, but also to understand the mechanisms involved.This thesis describes the synthesis and characterization of a novel manganese alkoxide and its use in sol–gel processing of magnetoresistive perovskite manganites. In searching for a soluble manganese alkoxide for sol–gel processing, we found that the methoxy-ethoxide, [Mn19O12(moe)14(moeH)10]·moeH, has a high solubility in appropriate organic solvents. Being 1.65 nm across, it is one of the largest alkoxides reported; it is also of interest because of its (for oxo-alkoxides) rare planar structure. After mixing with La, Nd, Ca, Sr, and Ba methoxy-ethoxides, [Mn19O12(moe)14(moeH)10]·moeH was used in the first purely alkoxide based sol–gel processing of perovskites manganites. The phase evolution on heating xerogel powders to 1000°C was studied, and thin films were prepared by spin-coating.It was found that the easily oxidised Mn-alkoxide facilitates the formation of high oxygen-excess modifications of the perovskites. The reactive precursor system yields fully hydrolysed gels almost without organic residues, but the gel absorbs CO2 from the air, leading to carbonate formation. The carbonate decomposition is the limiting step in oxide formation. Transport measurements of La0.67Ca0.33MnO3 films on LaAlO3 substrate show that all-alkoxide sol–gel derived films can compete with PLD films in terms of quality of epitaxy and transport. The somewhat different behaviour of the sol–gel derived films compared to PLD films is attributed to differences in morphology and oxygen stoichiometry.
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| 11. |
- Westin, Gunnar, et al.
(författare)
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All Alkoxide Sol-Gel Route to CoO-TiO2 Nano-Powders
- 2004
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Ingår i: Journal of Sol-Gel Science and Technology. ; :31, s. 25-29
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Tidskriftsartikel (refereegranskat)abstract
- CoO-TiO2 anatase materials have become highly interesting after the discovery of ferromagnetism above room-temperature, which makes them promising candidates for spintronic devices. There is however still uncertainty, and even contradictory ideas on the origin of the ferromagnetism and detailed microstructures ofthese materials. Here the synthesis and studies of CoO-doped TiO2 nano-phase powders with 0-12 mol% CoO using Co-methoxy-ethoxide and Ti(OPri)4 as precursors is presented. The amorphous precipitates or gels obtained by: (1) air hydrolysis and (2) quench hydrolysis with excess of water were amorphous and completely homogeneous in their Co:Ti ratio. Infrared (IR) spectroscopic and thermo-gravimetric (TG) studies showed that the air-hydrolysed samples Containrd a small amount of methoxy-ethoxide groups, besides coordinated water, while the quench-hydrolysed samples contained large amounts of coordinated water and lacked organic groups. According to the X-ray diffraction (XRD) patterns, the air-hydrolysed samples heated to 600°C contained both anatase and rutile. The rutile formationis ascribed to influence from the residual organic groups. The quench-hydrolysed precipitates yielded phase pure anatase at 480 and 600°C for the 0-6.7 mol% CoO range. At CoO contents of 8-12 mol%, the XRD i studies showed that anatase was obtained at 600°C, but in the 12% case, CoTiO3 was also detected. In addition, the 8-12 mol% samples showed two peaks in the Raman spectrum that might be due to CoO dissolved in anatase at high concentration. The studies were performed with TGA, IR and Raman-spectroscopy, XRD, scanning and transmission electron-microscopes (SEM and TEM, respectively) equipped with energy-dispersive X-ray spectrometers (EDS).
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| 12. |
- Westin, Gunnar, et al.
(författare)
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Preparation and Studies of ZnO:Al Films and Powders
- 2004
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Ingår i: Journal of Sol-Gel Science and Technology. ; 31, s. 283-286
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Tidskriftsartikel (refereegranskat)abstract
- ZnO:Al (0–10 at% Al) films and powders were produced using acac-modified methoxy-ethoxide precursors, obtained from Zn(C2H5)2 and Al4(OPri)12. The conversion to oxide powders was monitored with TGA and DSC, and the phase development was investigated with XRD, FT-IR spectroscopy, and TEM-EDS. The gels obtained by air-hydrolysis contained ca 0.5 acac/(Zn + Al) and a small amount of water and hydroxyls. All residual groups were removed to yield ZnO:Al by heating to ca 400°C. The powders obtained at 400 and 500°C were elementally homogeneous, and consisted of hex-ZnO:Al as ca 3–5 (10 at% Al) or 20–30 (3 at% Al) nm sized crystalline particles. Spin-coating on quartz, Si/SiO2, and window glass, followed by heating to 500°C resulted in 150–200 nm thick films of hex-ZnO:Al. 500 nm thick films were obtained by repeating the deposition and heat-treatment twice. The films were visually very clear and the measured transmittance high over the 400–800 nm range (91–93% at 800 nm) for ca 300 nm thick films.
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