Durability tests of solution-chemically derived spectrally selective absorbers
2005 (English)In: Solar Energy Materials and Solar Cells, Vol. 89, 197-207 p.Article in journal (Refereed) Published
A detailed neutron powder diffraction and calorimetric study was conducted to determine the influence of increasing Mn-substitution on the crystal and the magnetic structures of hematite, α-Fe2O3. The study was initiated to determine, if Mn substitution may be responsible for unusual ferromagnetic properties of natural hematite samples from the Kalahari Mn field, South Africa. Natural as well as synthetic Mn-bearing hematite samples with the compositional range Fe2−xMnxO3 (x=0 to 0.176) were examined. Calorimetric measurements were performed to determine the Néel TN and the Morin TM temperature transitions. All studied hematite samples, irrespective of chemical composition, display weak ferromagnetism at 295 K and coexistence of weak ferromagnetic and antiferromagnetic phases at 10 K. A slight decrease of the total magnetic moment and TM but a drastic decrease of TN can be attributed to increasing Mn-substitution. The results illustrate that Mn substitution may contribute but cannot be the sole reason for the unusual magnetic properties of natural hematite samples.
Place, publisher, year, edition, pages
2005. Vol. 89, 197-207 p.
Hematite, Substitution, Neutron powder diffraction, Calorimetry, Magnetic structure
IdentifiersURN: urn:nbn:se:uu:diva-77649OAI: oai:DiVA.org:uu-77649DiVA: diva2:105561
Cu3N is a promising material for optical data storage and copper metallisation. Upon heating the metastable Cu3N decomposes into metallic copper and nitrogen gas. Films have been grown with a novel ALD (Atomic Layer Deposition) process using copper(II) hexafluoroacetylacetonate (Cu(hfac)2), water and ammonia as precursors. By adding an intermediate water pulse the growth rate was enhanced on oxide substrates. The water was used with the purpose of producing sacrificial oxide layers. The mass changes during the deposition cycles were measured by in-situ Quartz Crystal Microbalance (QCM) technique. Extensive hfac removal was observed during Cu(hfac)2 adsorption, yielding a surface composition of Cu(hfac) 0.4 (ad) for short pulses.2006-03-212006-03-212011-01-11