TY - JOUR A1 - Grohmann, I. A1 - Kemnitz, E. A1 - Lippitz, Andreas A1 - Unger, Wolfgang T1 - Curve Fitting of Cr2p Photoelectron Spectra of Cr2O3 and CrF3 JF - Surface and interface analysis KW - Photoelektronenspektroskopie KW - Kurvenglättung KW - Chrom PY - 1995 SN - 0142-2421 SN - 1096-9918 VL - 23 SP - 887 EP - 891 PB - Wiley CY - Chichester AN - OPUS4-678 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Grohmann, I. A1 - Hess, A. A1 - Kemnitz, E. A1 - Frentrup, W. A1 - Unger, Wolfgang T1 - XANES-Investigations of coprecipitated AIF3/MgF2 phases T2 - BESSY Jahresbericht 1995 KW - XANES-Spektrum KW - Kalzienieren KW - Magnesium PY - 1996 SN - 0179-4159 SP - 222 EP - 223 PB - Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung CY - Berlin AN - OPUS4-682 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mehner, Hartmut A1 - Witke, Klaus A1 - Feist, M. A1 - Troyanov, S.I. A1 - Kemnitz, E. T1 - Halogenometallate von Übergangselementen mit Kationen stickstoffhaltiger heterozyklischer Basen. VII Zwei Oxidationsstufen und vier verschiedene Koordinationen von Eisen in einer Verbindung. Synthese, Kristallstruktur und spektroskopische Charakterisierung von 1,4-Dimethylpiperazinium-Chloroferrat(II, III), (dmpipzH2)6[FeIICl4]2[FeIIICl4]2[FeIICl5] [FeIIICl6] JF - Zeitschrift für anorganische und allgemeine Chemie = Journal of inorganic and general chemistry KW - Halogenometallate KW - Spektroskopische Charakterisierung PY - 1999 SN - 0044-2313 SN - 1521-3749 SN - 0372-7874 SN - 0863-1786 SN - 0863-1778 N1 - Sprachen: Deutsch/Englisch - Languages: German/English VL - 625 IS - 1 SP - 141 EP - 146 PB - Wiley-VCH CY - Weinheim AN - OPUS4-738 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Feist, M. A1 - Troyanov, S.I. A1 - Mehner, Hartmut A1 - Witke, Klaus A1 - Kemnitz, E. T1 - Zwei Oxidationsstufen und vier verschiedene Koordinationen von Eisen in einer Verbindung. Synthese, Kristallstruktur und spektroskopische Charakterisierung von 1,4-Dimethylpiperazinium-Chloroferrat(II, III), (dmpipzH2)6[FeIICl4]2[FeIIICl4]2[FeIICl5] [FeIIICl6] JF - Zeitschrift für anorganische und allgemeine Chemie = Journal of inorganic and general chemistry KW - 1,4-Dimethylpiperazinium chloroferrate(II,III) KW - Crystal Structure KW - Trigonal-bipyramidal pentachloroferrate(II) KW - Mössbauer, Raman spectroscopy PY - 1999 SN - 0044-2313 SN - 1521-3749 SN - 0372-7874 SN - 0863-1786 SN - 0863-1778 IS - 625 SP - 141 EP - 146 PB - Wiley-VCH CY - Weinheim AN - OPUS4-2305 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Witke, Klaus A1 - Kunze, Ralf A1 - Neubert, Dietmar A1 - Mehner, Hartmut A1 - Feist, M. A1 - Kemnitz, E. T1 - Two oxidation states and four different coordinations of iron in an unusual chloro complex: TG-MS, Raman and Mössbauer spectroscopic investigations of the thermal behaviour JF - Thermochimica Acta N2 - Conventional simultaneous thermal analysis, capillary-coupled TG–MS, in situ and ex situ Raman and Mössbauer spectroscopy, as well as chemical analysis have been used for the investigation of the first decomposition step of the mixed valence chloroferrate (dmpipzH2)6[Fe(II)Cl4]2[Fe(III)Cl4]2[Fe(II)Cl5][Fe(III)Cl6]. Under argon at ca. 200°C, an almost complete reduction proceeds in a solid state reaction forming Fe(II). It is accompanied by the release of HCl and, to a minor degree, carbon containing species. A multi-phase product with at least two chloroferrate species, coke, and C,H,N-containing polymers is formed. Binuclear iron complexes, such as (dmpipzH)2[Fe(II)2Cl6], and small amounts of (dmpipzH)[Fe(III)Cl4] have been proposed to be the major and minor component of the product mixture, respectively. KW - Mixed valence chloroferrate KW - Thermal decomposition KW - Intramolecular reduction PY - 2000 DO - https://doi.org/10.1016/S0040-6031(00)00546-3 SN - 0040-6031 SN - 1872-762X VL - 361 IS - 1-2 SP - 53 EP - 60 PB - Elsevier CY - Amsterdam AN - OPUS4-988 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lippitz, Andreas A1 - Unger, Wolfgang A1 - Boese, O. A1 - Kemnitz, E. T1 - y-Al2O3 by Au 4f7/2-referenced XPS and XAES JF - Surface science spectra N2 - Powder x-ray diffraction (XRD) defined -Al2O3 has been investigated by x-ray photoelectron spectroscopy (XPS) and x-ray excited Auger electron spectroscopy (XAES). The Au 4f7/2 orbital is used for static charge referencing. This feature originates from well-defined and chemically inert 20 nm highly dispersed gold particles deposited on the sample surface. The particles, with a narrow particle size distribution, were obtained from a highly purified colloidal solution (sodium concentration below 1 mg/l). This procedure allows a determination of gold-referenced XPS and XAES data sets. ©2001 American Vacuum Society. KW - Au 4f referenced XPS data KW - Aluminium KW - Oxide PY - 2001 UR - http://scitation.aip.org/vsearch/servlet/VerityServlet?KEY=SSSPEN&ONLINE=YES&smode=strresults&sort=chron&maxdisp=25&threshold=0&possible1zone=article&possible4=lippitz&possible4zone=author&bool4=and&fromyear=2001&OUTLOG=NO&viewabs=SSSPEN&key=DISPLAY&docID DO - https://doi.org/10.1116/11.20020305 SN - 1055-5269 SN - 1520-8575 VL - 8 IS - 1-4 SP - 214 EP - 219 PB - AIP CY - Woodbury, NY AN - OPUS4-1910 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mehner, Hartmut A1 - Feist, M. A1 - Stößer, R. A1 - Scholz, G. A1 - Kemnitz, E. A1 - Dwelk, H. T1 - Halogeno metallates of transition elements with cations of nitrogen-containing heterocyclic bases, IX. Moessbauer and ESR spectroscopic investigation of aquachloro- and bromoferrates(III). On the compatibility of structural information obtained by spectroscopic and diffraction methods JF - Solid state sciences N2 - The 57Fe-Moessbauer spectrum of (dmpipzH2)2[FeIII(H2O)2Cl4][FeIII Cl4]Cl2 (1) consists of two doublets caused by a strongly distorted octahedral and a non-distorted tetrahedral component. Both (dmpipzH2)[FeIIIBr4]2 (2) and (trienH2)[FeIIIBr4]Br (3) show only one doublet indicating a more strongly distorted iron(III) species for 2 and a less-distorted one in the case of 3. For all compounds investigated, the ESR spectra reveal the existence of ground states with predominant antiferromagnetic coupling. The Néel temperatures amount to <4.2 K for 1, 4 K for 3 and 48 K for 2. In the case of 2, both the Moessbauer and the ESR spectra reveal the formation of exchange-coupled {FeBr4} units which has been attributed to a significant cation influence. The fine structure of residual paramagnetic [FeBr4]- subunits remaining in the crystalline matrix could be directly determined. Temperature dependent AC and DC susceptibility measurements of 2 and 3 confirmed the results. KW - Iron coordination KW - Antiferromagnetic coupling KW - Exchange-coupled units KW - ESR fine structure KW - Magnetic susceptibility PY - 2002 DO - https://doi.org/10.1016/S1293-2558(01)01193-1 SN - 1293-2558 SN - 1873-3085 VL - 4 IS - 1 SP - 109 EP - 115 PB - Elsevier CY - Amsterdam AN - OPUS4-1311 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kemnitz, E. A1 - Zhu, Y. A1 - Adamczyk, Burkart T1 - Enhanced Lewis acidity by aliovalent cation doping in metal fluorides JF - Journal of fluorine chemistry N2 - A model regarding the generation of acidity in binary metal fluorides has been proposed and its validity has been examined for several binary fluoride systems with the general compositions MF3/M'F3 and MF2/M'F3. In accordance with this hypothesis, the binary systems (CrF3/AlF3, CrF3/FeF3 and AlF3/VF3) do not show acidities larger than the sum of the acidities of the component fluorides. The hypothesis predicts the generation of Lewis acidity when MF2 is the major component (host) and generation of Brønsted acidity when MF3 acts as the host for the MF2/M'F3. The experimental results (surface acidity and catalytic activity) confirmed the predictions made from this hypothesis for binary combinations MgF2/ M'F3 (M'=Cr, Al, Fe, V). The application of this model is discussed in terms of other parameters: ionic radii and the fluoride affinity of the metal fluorides involved. PY - 2002 DO - https://doi.org/10.1016/S0022-1139(02)00022-2 SN - 0022-1139 SN - 1873-3328 VL - 114 SP - 163 EP - 170 PB - Elsevier CY - Amsterdam AN - OPUS4-1661 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Böse, Olaf A1 - Unger, Wolfgang A1 - Kemnitz, E. A1 - Schroeder, S. L. M. T1 - Active sites on an oxide catalyst for F/Cl-exchange reactions: X-ray spectroscopy of fluorinated y-Al2O3 JF - Physical chemistry, chemical physics N2 - The dismutation of CHClF2 to CHF3 and CHCl3 was used to probe the effect of γ-Al2O3 fluorination on fluorine-against-chlorine (Cl/F) exchange reactions. X-ray photoelectron spectroscopy (XPS), X-ray excited Auger electron spectroscopy (XAES) and X-ray absorption near edge structure (XANES) spectroscopy were employed to probe the modifications at the surface of γ-Al2O3 accompanying the initial stages of fluorination. The results suggest that fluorine uptake by γ-Al2O3 starts initially at the surface of the oxide particles, with the formation of a fluorine species that is characterised by a single bond and a high effective charge q. Catalytic Cl/F-exchange is only observed after accumulation of higher fluorine concentrations, for which insertion of fluorine into the sub-surface region of the oxide crystallites has commenced. Quantitative XPS shows that the fluorination level must exceed approximately 10 atom% of the anions to achieve catalytic activity. The spectroscopic evidence suggests that the formation of aluminium oxofluorides is sufficient to provide catalytic activity. The presence of an AlF3 phase is not a condition for the observation of catalytic activity, even though defect-rich AlF3 is ultimately the endpoint of the fluorination process and is itself a Cl/F exchange catalyst. PY - 2002 DO - https://doi.org/10.1039/b110792e SN - 1463-9076 SN - 1463-9084 VL - 4 IS - 12 SP - 2824 EP - 2832 PB - The Royal Soc. of Chemistry CY - Cambridge AN - OPUS4-6940 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ünveren, Ercan A1 - Kemnitz, E. A1 - Hutton, S. A1 - Lippitz, Andreas A1 - Unger, Wolfgang T1 - Analysis of highly resolved x-ray photoelectron Cr 2p spectra obtained with a Cr2O3 powder sample prepared with adhesive tape JF - Surface and interface analysis KW - High-resolution XPS KW - Cr2O3 powder KW - Multiplet splitting PY - 2004 SN - 0142-2421 SN - 1096-9918 VL - 36 SP - 92 EP - 95 PB - Wiley CY - Chichester AN - OPUS4-3427 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scheurell, K. A1 - Hoppe, E. A1 - Brzezinka, Klaus-Werner A1 - Kemnitz, E. T1 - Bulk and surface properties of highly dispersed VOx/ZrO2, VOx/SiO2 and VOx/TiO2/SiO2 systems and their relevance for propane oxidation JF - Journal of materials chemistry N2 - Highly dispersed vanadium-doped metal oxides such as VOx/ZrO2, VOx/SiO2 and VOx/TiO2/SiO2 with vanadium contents between 0 and 25 mole% were prepared by special bulk preparation methods (coprecipitation and sol–gel, followed by freeze-drying). Bulk and surface properties of the obtained mixed oxide solid solutions were thoroughly investigated by different analytical methods (Raman and FTIR spectroscopy, TPD, H2-TPR, oxygen isotope measurements etc.). Moreover, the catalytic behaviour of the oxides was studied for the example of the oxidative dehydrogenation (ODH) of propane to propylene. Independent of the preparation method, the catalytic behaviour of vanadium-doped ZrO2 and TiO2 phases is very similar. Both metal oxide solid solutions are very active in propane ODH whereas the catalytic activity of VOx/SiO2 is relatively low. On the other hand, the reduction of the catalytic activity is accompanied by an improved selectivity for the formation of propylene. The correlation between the catalytic activity and the acidity of the oxide systems is discussed. Oxidation experiments with 18O2 clearly show that the ODH reaction occurs according to the Mars–van Krevelen mechanism. KW - Vanadium-doped metal oxides KW - Solid solutions KW - Coprecipation KW - Sol-gel-method KW - Propan oxidation KW - Catalytic activity KW - Oxygen mobility PY - 2004 DO - https://doi.org/10.1039/b402924k SN - 0959-9428 SN - 1364-5501 VL - 14 IS - 16 SP - 2560 EP - 2568 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-4152 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ünveren, Ercan A1 - Kemnitz, E. A1 - Oran, Umut A1 - Unger, Wolfgang T1 - Static TOF-SIMS Surface Analysis of a CCl2F2 Activated Chromia Catalyst Used for a Cl/F Exchange Reaction JF - The journal of physical chemistry / B N2 - Static TOF-SIMS results strongly underpin earlier conclusions from ESCA, XANES, and tracer studies that the accumulation of fluorine and chlorine at the surface of chromia by a heterogeneous reaction with a chlorofluorocarbon compound results in the formation of mixed chromium oxide halide species and not in the nucleation of CrCl3 and/or CrF3 phases. KW - Oberflächenanalytik KW - Katalyse PY - 2004 DO - https://doi.org/10.1021/jp046773h SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 108 SP - 15454 EP - 15456 PB - Soc. CY - Washington, DC AN - OPUS4-4718 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krishna Murthy, J. A1 - Gross, U. A1 - Rüdiger, St. A1 - Ünveren, Ercan A1 - Unger, Wolfgang A1 - Kemnitz, E. T1 - Synthesis and characterization of chromium(III)-doped magnesium fluoride catalysts JF - Applied physics A N2 - Cr3+-doped MgF2 systems are synthesised by a novel non-aqueous soft chemistry route using different Cr precursors and varying Cr loading. These systems have been characterized by X-ray powder diffraction (XRD), BET surface area, TPD of ammonia, FT-IR pyridine adsorption analysis and X-ray photoelectron spectroscopy, and tested for their catalytic activity in dismutation of CCl2F2 and CF3–CHClF. Catalysts synthesised starting from CrO3 or (CH3CO2)7Cr3(OH)2 showed better catalytic activity than those prepared with CrCl3. FT-IR pyridine adsorption studies reveal that the catalytic activity is highly correlated with the Lewis acid strength. In TPD of NH3 catalysts prepared from CrO3 and (CH3CO2)7Cr3(OH)2, precursors showed a similar behaviour, different from that of catalysts prepared from CrCl3. KW - Lewis acid KW - Heterogeneous catalysis KW - Metal fluoride KW - Doped systems PY - 2005 UR - http://www.sciencedirect.com/science/journal/0926860X DO - https://doi.org/10.1016/j.apcata.2004.12.004 SN - 0947-8396 VL - 282 IS - 1-2 SP - 85 EP - 91 PB - Springer CY - Berlin AN - OPUS4-7442 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ünveren, Ercan A1 - Kemnitz, E. A1 - Lippitz, Andreas A1 - Unger, Wolfgang T1 - Surface Characterization of Chromia for Chlorine/Fluorine Exchange Reactions JF - The journal of physical chemistry / B N2 - The dismutation of CCl2F2 was used to probe the effect of halogenation of chromia by Cl/F exchange reactions to find out the difference between the halogenated inactive and active catalysts. The heterogeneous reactions were performed in a continuous flow Ni reactor and also under simulated reaction conditions in a reactor where after the reaction X-ray photoelectron spectroscopy (XPS) and X-ray excited Auger electron spectroscopy (XAES) analyses are possible without air exposure of the catalyst, i.e., under so-called "in situ" conditions. The Cr(III) 2p XP spectra, which revealed multiplet splitting features and satellite emission, were used for chemical analysis by using a simple evaluation procedure which neglects this inherent complexity. Chemical analysis was also applied by using chemical state plots for Cr 3s in order to cross-check Cr 2p related results. Both ex and in situ XPS show that as soon as Cr2O3 is exposed to CCl2F2 at 390°C fluorination as well as chlorination takes place at the catalyst surface. When the XPS surface composition reaches approximately 4 at. % fluorination and 6 at. % chlorination, maximum catalytic activity was obtained. Application of longer reaction times did not change significantly the obtained surface composition of the activated chromia. The fluorination and chlorination of chromia was further investigated by various HF and HCl treatments. The activated chromia samples and the Cr2O3, Cr(OH)3, CrF2OH, CrF3·H2O, α-CrF3, β-CrF3, and CrCl3 reference samples with well-known chemical structures were also characterized by X-ray absorption near edge structure (XANES), time-of-flight secondary ion mass spectroscopy (TOF-SIMS), pyridine-FTIR, wet chemical (F and Cl) analysis, X-ray powder diffraction (XRD), and surface area (BET) analysis. The results suggest that the formation of chromium oxide chloride fluoride species, e.g., chromium oxide halides, at the surface is sufficient to provide catalytic activity. The presence of any CrF3 and/or CrCl3 phases on the activated chromia samples was not found. PY - 2005 DO - https://doi.org/10.1021/jp045902r SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 109 IS - 5 SP - 1903 EP - 1913 PB - Soc. CY - Washington, DC AN - OPUS4-10531 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Murthy, J.K. A1 - Gross, U. A1 - Rüdiger, S. A1 - Ünveren, Ercan A1 - Unger, Wolfgang A1 - Kemnitz, E. T1 - Synthesis and characterization of chromium(III)-doped magnesium fluoride catalysts JF - Applied catalysis / A N2 - Cr3+-doped MgF2 systems are synthesised by a novel non-aqueous soft chemistry route using different Cr precursors and varying Cr loading. These systems have been characterized by X-ray powder diffraction (XRD), BET surface area, TPD of ammonia, FT-IR pyridine adsorption analysis and X-ray photoelectron spectroscopy, and tested for their catalytic activity in dismutation of CCl2F2 and CF3–CHClF. Catalysts synthesised starting from CrO3 or (CH3CO2)7Cr3(OH)2 showed better catalytic activity than those prepared with CrCl3. FT-IR pyridine adsorption studies reveal that the catalytic activity is highly correlated with the Lewis acid strength. In TPD of NH3 catalysts prepared from CrO3 and (CH3CO2)7Cr3(OH)2, precursors showed a similar behaviour, different from that of catalysts prepared from CrCl3. KW - Lewis acid KW - Heterogeneous catalysis KW - Metal fluoride KW - Doped systems PY - 2005 SN - 0926-860X SN - 1873-3875 VL - 282 IS - 1-2 SP - 85 EP - 91 PB - Elsevier CY - Amsterdam AN - OPUS4-11953 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - König, R. A1 - Scholz, G. A1 - Kemnitz, E. A1 - Jäger, Christian A1 - Pawlik, Alf A1 - van Rossumm, B. A1 - Oschkinat, H. T1 - Crystalline aluminium hydroxy fluorides: Structural insights obtained by high field solid state NMR and 27Al chemical shift trend analysis T2 - Gesellschaft Deutscher Chemiker T2 - Gesellschaft Deutscher Chemiker CY - Regensburg, Germany DA - 2008-09-22 PY - 2008 AN - OPUS4-17956 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - König, R. A1 - Scholz, G. A1 - Kemnitz, E. A1 - Jäger, Christian A1 - Pawlik, Alf A1 - van Rossumm, B. A1 - Oschkinat, H. T1 - Crystalline aluminium hydroxyl fluorides: Structural insights obtained by high-field solid state NMR and 27Al chemical shift trend analysis T2 - Gesellschaft Deutscher Chemiker T2 - Gesellschaft Deutscher Chemiker CY - Regensburg, Germany DA - 2008-09-22 PY - 2008 AN - OPUS4-17957 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krüger, Hannes A1 - Kemnitz, E. A1 - Hertwig, Andreas A1 - Beck, Uwe T1 - Transparent MgF2-films by sol-gel coating: Synthesis and optical properties JF - Thin solid films N2 - Dielectric, anti-reflective or high reflective systems consist of low and high refractive index layers. Common systems are oxides. The preparation of low refractive index MgF2-films of optical quality by means of an anhydrous low temperature sol–gel synthesis is presented. The MgF2-sol is prepared by spin-coating on silicon and glass substrates. Various film thicknesses between 20 nm and 435 nm have been deposited. It has been shown that the thickness increase is proportional to the number of coating steps. The deposited MgF2-films consist of 10 nm to 20 nm large nanoparticles and have smooth surfaces with an average roughness (Ra) of (1.7 ± 0.3) nm. The optical constants n and k of the films are in agreement with the literature data of bulk-MgF2. KW - Sol-gel KW - Nano-MgF2 KW - Spin coating KW - Optical properties KW - Nanoparticles PY - 2008 DO - https://doi.org/10.1016/j.tsf.2007.10.126 SN - 0040-6090 VL - 516 IS - 12 SP - 4175 EP - 4177 PB - Elsevier CY - Amsterdam AN - OPUS4-17375 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - König, R. A1 - Scholz, G. A1 - Pawlik, Alf A1 - Jäger, Christian A1 - van Rossumm, B. A1 - Oschkinat, H. A1 - Kemnitz, E. T1 - Crystalline Aluminium Hydroxy Fluorides: Structural Insights Obtained by High Field Solid State NMR and Trend Analyses JF - The journal of physical chemistry / C N2 - A series of crystalline aluminum hydroxy fluorides in cubic pyrochlore structure AlFx(OH)3-x·H2O with variable F-content x were investigated by solid-state NMR by applying different magnetic fields up to 21.1 T. Distinguishable octahedral species AlFx(OH)6-x (x = 1-6) were identified in the crystalline aluminum hydroxy fluorides. The subsequent analysis of the highfield 27Al MAS NMR data allows the derivation of the trend analysis graphs giving correlations between the 27Al chemical shifts and the quadrupolar frequencies and the F-content x in AlFx(OH)6-x. Clear trends were obtained for both, which are, along with the 19F MAS chemical-shift trend analysis presented earlier, valuable tools for the interpretation of MAS NMR spectra of amorphous AlFx(OX)3-x compounds (X = H, alkyl). Following the dehydration of the pyrochlores by solid-state NMR eventually reveals a remarkable influence of the incorporated solvent molecules (H2O) on the 19F chemical shift. On that basis, a new chemical-shift trend analysis for 19F chemical shifts in correlation with x in AlFx(OH)6-x units for proton-poor substances (in the Al, F, O, H system) was determined. By using this correlation, high-surface AlF3 has a mean bulk Al:F ratio similar to that found for ACF, namely, AlF2.8(O/OH)0.2. KW - Aluminium-27 KW - Crystalline aluminium hydroxy fluorides KW - Chemical shift trend analysis KW - High field solid state NMR KW - Quadrupolar nuclei PY - 2008 DO - https://doi.org/10.1021/jp804662f SN - 1932-7447 SN - 1089-5639 VL - 112 IS - 40 SP - 15708 EP - 15720 PB - Soc. CY - Washington, DC AN - OPUS4-18365 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krüger, Hannes A1 - Kemnitz, E. A1 - Hertwig, Andreas A1 - Beck, Uwe T1 - Moderate temperature sol-gel deposition of magnesium fluoride films for optical UV-applications: A study on homogeneity using spectroscopic ellipsometry JF - Physica status solidi A N2 - Thin films of MgF2 have been deposited on silicon wafers in optical quality with a novel sol-gel deposition process at temperatures as low as 100 °C. The properties of the fluoride layers are compared to bulk MgF2 with respect to the optical constants. By employing spectroscopic mapping ellipsometry, the uniformity of the thickness of fluoride layers is confirmed to be within acceptable limits for optical applications. The optical constants are close to the bulk data. High-quality low-index films of suitable and homogeneous thickness have already been produced on a laboratory scale. KW - 78.20.-e KW - 78.66.Li KW - 78.68.+m KW - 81.20.Fw PY - 2008 DO - https://doi.org/10.1002/pssa.200777856 SN - 1862-6300 SN - 0031-8965 VL - 205 IS - 4 SP - 821 EP - 824 PB - Wiley-VCH CY - Berlin AN - OPUS4-17330 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -