IPG Photonics

About: IPG Photonics is a based out in . It is known for research contribution in the topics: Laser & Fiber laser. The organization has 903 authors who have published 1241 publications receiving 63339 citations.

Behavior of paramagnetic iron during the thermal transformations of kaolinite

Abstract: Kaolinites with various degrees of structural order and iron content were heated and subsequently analyzed via electron paramagnetic resonance. Iron was present in two different states in the heated materials, either as dilute structural Fe 3+ ions or in concentrated Fe 3+ phases. During metakaolinization, the environment of dilute Fe 3+ ions changed, following modifications of the Al 3+ coordination, and the Fe 3+ concentration increased. With the breakdown of metakaolinite, the diffusion of Fe 3+ ions induced their exsolution in superparamagnetic iron-rich domains (Fe 3+ clusters in γ-Al 2 O 3 and/or Fe 3+ oxide nanophases), which produced a decrease in the dilute Fe 3+ concentration. The subsequent breakdown of γ-Al 2 O 3 and the formation of mullite made the dilute Fe 3+ concentration increase again, because of the incorporation of Fe 3+ ions in the mullite structure.

X‐ray magnetic circular dichroïsm provides strong evidence for tetrahedral iron in ferrihydrite

Abstract: [1] Ferrihydrite is an important iron oxyhydroxide for earth and environmental sciences, biology, and technology. Nevertheless, its mineral structure remains a matter of debate. The stumbling block is whether a significant amount of tetrahedrally coordinated iron is present. Here we present the first X-ray magnetic circular dichroism (XMCD) measurements performed on a well characterized synthetic sample of 6-line ferrihydrite, at both K and L2,3energy edges of iron. XMCD results demonstrate unambiguously the presence of tetrahedrally coordinated Fe(III) in the mineral structure, in quantities compatible with the latest extended X-ray absorption fine structure (EXAFS) analyses suggesting a concentration of 20–30%. Moreover, we find an antiferromagnetic coupling between tetrahedral and octahedral sublattices, with the octahedral sublattice parallel to the external magnetic field.

The structure of SiO2–GeO2 glasses: A spectroscopic study

Abstract: FourglassesoftheSiO2–GeO2binarysystemhavebeensynthesizedviaasol–gel routefollowedbyaheattreatmentandaquench. GlassstructurehasbeendeterminedbyGeK-edgeX-rayabsorptionspectroscopy(XAS)atlowtemperatureandRamanspectroscopy. ThesemixedglassespresentacontinuousrandomnetworkofinterconnectedGeO4andSiO4tetrahedra,withGeO4tetrahedrasimilarto theGeO4unitsinGeO2glassandcontinuouscompositional variationsfromGeO2-richregionstoSiO2-richregions. Sucharandom mixtureisconsistent withphysical propertiesof thesebinaryglassesaswell aswiththechemical dependenceof theirpolyamorphism athighpressure.ThisEXAFS-derivedmeanGe–O–SianglesareclosetotheGe–O–GemeanangleinGeO2glass,134