Investigation of Al diffusion in different oxide thin-film layers by SNMS/HFM method

Depth profiles of Ga₂O₃/a-SiO₂/Al₂O₃- substrate, Ga₂O₃/a-Si₃N₄/Al₂O₃- substrate, and Ga₂O₃/Al₂O₃ substrate thin layers were determined by the SNMS/HFM method. Al diffusion from the Al₂O₃ substrate was investigated after 50, and in some cases after 600 hours of heat treatment time at different temperatures (600 °C,850 °C,950 °C,1050 °C and 1150 °C). The diffusion coefficient of Al at 850 °C was found to be D _Al=8.7 * 10^–18 cm²/s in amorphous SiO₂; D _Al=1.5*10^–17 cm²/s in amorphous Si₃N₄ and D _Al=5.5* 10^–16 cm²/s in Ga₂O₃ at 600 °C, respectively. The possible diffusion mechanism is explained in terms of the metal-oxygen bond-strengths. Although the studied materials have high resistivity at room temperature, the applied SNMS/HFM method has proven to be an efficient surface analytical tool even in these cases.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Determination of the bond-angle distribution in vitreous B2O3 by B double rotation (DOR) NMR spectroscopy

The B–O–B bond angle distributions for both ring and non-ring boron sites in vitreous B₂O₃ have been determined by ¹¹B double rotation (DOR) NMR and multiple-quantum (MQ) DOR NMR. The [B₃O₆] boroxol rings are observed to have a mean internal B–O–B angle of 120.0±0.7° with a small standard deviation, σ_R=3.2±0.4°, indicating that the rings are near-perfect planar, hexagonal structures. The rings are linked predominantly by non-ring [BO₃] units, which share oxygens with the boroxol ring, with a mean B_ring–O–B_non-ring angle of 135.1±0.6° and σ_NR=6.7±0.4°. In addition, the fraction of boron atoms, f, which reside in the boroxol rings has been measured for this sample as f=0.73±0.01.     

Kombination wirksamer Trennverfahren mit modernen analytischen Methoden in der Naturstoffchemie

Zusammenfassung Aus Crotonöl konnten durch Anwendung multiplikativer Verteilungs- und chromatographischer Verfahren die entzündlichen und cocarcinogenen Substanzen A1–A4 und B1–B7 rein dargestellt werden. Diese Substanzen sind Diester des polyfunktionellen Diterpenalkohols Phorbol, C₂₀H₂₈O₆ mit jeweils einer kurzkettigen (Essig-, (+)-S-2-Methylbutter-, Tiglinsäure) und einer langkettigen Fettsäure (Capryl-, Caprin-, Laurin-, Myristin-, Palmitinsäure). Die Teilsynthese einiger Substanzen wird angegeben. Aus den UV-, IR- und KMR-Daten und chemischen Befunden werden Teilformeln für Phorbol abgeleitet und diskutiert.

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Summary The compounds A1–A4 and B1–B 7 have been isolated from croton oil in pure state by multiplicative distribution and chromatography. These compounds are di-esters of the polyfunctional diterpene alcohol phorbol C₂₀H₂₈O₆ each with a short chain (acetic-, (+)-S-2-methyl-butanoic-, tiglic acid) and a long chain fatty acid (octanoic-, decanoic-, dodecanoic-, tetradecanoic-, hexadecanoic acid). The partial synthesis of some compounds is described. From ultraviolet-, infrared-, nmr-spectra and from chemical evidence partial structures for phorbol are being discussed.

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Für die Messung von KMR-, Massen- und CD-Spektren und anregende Diskussionen danken wir den Herren Dr. J. Sonnenbichler, München, Dr. J. Jochems, Heidelberg, Dr. A. Mannschreck, Heidelberg, Dr. H. Budzikiewicz, Braunschweig, Dipl.-Chem. C. Wünsche, Heidelberg, Doz. Dr. G. Snatzke, Bonn, und V. Scheidel, Heidelberg.

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Vorgetragen von H. Kubinyi.     

Synthesis of Polymer Films by an Electron Emission CVD Technique

A low-pressure chemical vapor deposition (CVD) technique based on the formation of reactive film precursors by dissociation of gas-phase reactants by electron impact is described. The electrons are emitted by a hot filament and a positive bias voltage applied to the substrate provides control of the emission current. The emitted electrons are primarily responsible for the gas dissociation, but secondary electrons resulting from electron-impact ionization of the gas molecules also produce reactive species, contributing to the deposition process. This technique was used to synthesize polymer films from C₂H₂–N₂ mixtures at pressures ranging from 1–10 Pa. The dependencies of the current collected by the substrate, I_S, on the substrate bias voltage, V_S, and on the gas pressure were determined. The film deposition rate was measured as a function of several deposition variables such as I_S, V_S, and the N₂ to C₂H₂ flow rate ratio. Oxygen was present in the films as a contaminant. Analyses by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) provided insight into the film molecular structure, allowing identification of various functional groups and binding states of the C- and N–atoms. From the XPS spectra, the N/C and O/C ratios were determined.     

Solid-state synthesis of boron subnitride, B6N: myth or reality?

Solid-state synthesis of boron subnitride, B₆N, as a result of chemical interaction between boron and boron nitride at 7.5 GPa and 1700 °C has been previously reported by Hubert et al. However, a critical analysis of the results has shown that the evidence for the formation of boron subnitride with B₆O-like structure is inconclusive. We have studied in situ the interaction between boron and BN at the same p–T conditions using X-ray diffraction with synchrotron radiation. At 7.4 GPa and 1700 °C the formation of a new phase has not been observed. At the same time, HP–HT treatment has resulted in strong and unpredictable preferred orientation of boron crystallites. This leads to the rise of some weak boron reflections that might be erroneously attributed to the appearance of a new phase. To cite this article: V.L. Solozhenko et al., C. R. Chimie 9 (2006).     

Notiz zur polarographischen Bestimmung von Nickelspuren in Kobalt und Reinstkobaltsalzen

Zusammenfassung Die Stabilitätskonstante des Molybdän(V)-oxinatkomplexes wurde spektralphotometrisch und durch Austauschmessungen zu K=1,39 · 10^–12 ± 0,02 bestimmt. Beide Verfahren zeigen eine sehr gute Übereinstimmung. Der Komplex ist in 50%igem Aceton-Wasser über 3 Std stabil und kann analytisch zur Spurenbestimmung nach der Methode von Busev u. Fan verwendet werden.

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Summary The stability constant of Mo₂O₃(C₉H₆NO)₄ was determined spectrophotometrically and by displacement reactions as K=1.39 · 10^–12 ± 0.02. Both methods gave the same results. The complex is stable over three hours in 50% acetone and at pH 4.0 and can be employed for the determination of traces of molybdenum by the method of Busev and Fan.

     

Ionophoretische Trennung von ReCl62?, ReBr62? und ReO4?

Zusammenfassung Es wurde die ionophoretische Trennung von ReCl₆ ^2–, ReBr₆ ^2– und ReO₄ ^– unter Verwendung verschiedener Papiersorten untersucht. Am geeignetsten erwies sich das Papier 2045 b Gl von Schl. & Sch.

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Summary The ionophoretic separation of ReCl₆ ^2–, ReBr₆ ^2–, and ReO₄ ^– has been examined using different kinds of paper. Best results have been obtained with the paper 2045 b Gl from Schleicher & Schüll.

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Herrn Prof. G. Brauer danke ich für Förderung. Für die Überlassung von Rheniumverbindungen bin ich der Fa. W. C. Heraeus, Hanau, verpflichtet. Die Neutronenaktivierung wurde freundlicherweise von den Herren Dr. Marth und Dr. Köhler von der Reaktorstation in Garching bei München vorgenommen. Das Bundesministerium für Atomkernenergie und Wasserwirtschaft unterstützte die Untersuchung durch eine Sachbeihilfe.     

TSL and EPR studies of SrBPO5 doped with CeO2and co-doped with CeO2 and Sm2O3

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) investigations were carried out on gamma irradiated SrBPO₅ samples doped with CeO₂ and co-doped with CeO₂ and Sm₂O₃. On gamma-irradiation at room temperature, BO₃ ^2–, O₂ ^– and O^– radicals were produced. It was seen that the O^– radical ion disappeared in the sample annealed at 500 K. It is proposed that the recombination between trapped electrons and O^– radical ions results in transfer of recombination energy to the impurity centre Ce³⁺ resulting in TSL glow peak at 485 K. In the case of co-doped samples energy transfer occurs between Ce³⁺ to Sm³⁺ resulting in increase in the intensity of glow peak at 485 K.The authors are grateful to Dr. V. K. Manchanda, Head, Radiochemistry Division, BARC for his keen interest and encouragement during the course of this work.     

TSL and EPR studies of SrBPO5 doped with CeO2 and co-doped with CeO2 and Sm2O3

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) investigations were carried out on gamma irradiated SrBPO₅ samples doped with CeO₂ and co-doped with CeO₂ and Sm₂O₃. On gamma-irradiation at room temperature, BO₃ ^2–, O₂ ^– and O^– radicals were produced. It was seen that the O^– radical ion disappeared in the sample annealed at 500 K. It is proposed that the recombination between trapped electrons and O^– radical ions results in transfer of recombination energy to the impurity centre Ce³⁺ resulting in TSL glow peak at 485 K. In the case of co-doped samples energy transfer occurs between Ce³⁺ to Sm³⁺ resulting in increase in the intensity of glow peak at 485 K.The authors are grateful to Dr. V. K. Manchanda, Head, Radiochemistry Division, BARC for his keen interest and encouragement during the course of this work.     

Magnetic structure of the UCuxSi2−x system

Neutron powder diffraction experiments were performed on selected compositions of the UCu_xSi_2−x system exhibiting an interesting magnetic phase diagram towards the composition: spin fluctuation behaviour for x<0.49, ferromagnetism for 0.49≤x<0.80, spin glass state for 0.80<x<0.92 and finally antiferromagnetism for 0.92<x≤0.96. At 1.5 K, the compounds UCu_0.49Si_1.51 (hexagonal AlB₂ modification) and UCu_0.65Si_1.35 show a collinear ferromagnetic structure where the uranium magnetic moments equal to 1.1(1) and 2.5(1)μ_B, respectively, are aligned in the basal plane of the [U₆] trigonal prisms. On the contrary, UCu_0.96Si_1.04 adopts a non-collinear antiferromagnetic structure similar to that observed for UCuSn. Moreover, the study confirms the absence of long range magnetic order for UCu_0.90Si_1.10.     

Zur metall-ring-bindung in sandwich-komplexen

Zusammenfassung Die Anwendung des einfachen LCAO-MO-Näherungsverfahrens von Wolfsberg und Helmholz auf Sandwich-Komplexe liefert für Ferrocen und Dibenzolchrom im Bereich bindender MO's bemerkenswerte Übereinstimmungen mit SCF-Rechnungen von Schustorowitsch und Djatkina.Die mittels SCF-Wellenfunktionen gefundenen Überlappintegrale von Komplexen des Typs (C _nH_n)₂Me(n=4–8) weisen auch für n=7 und 8 noch relativ günstige Überlappungsbedingungen auf.Die prinzipiell mögliche Beteiligung von f-Orbitals an der Bindung des hypothetischen Komplexes (C ₈H₈)₂U wird diskutiert.

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The application of the simple LCAO-MO-approach of Wolfsberg and Helmholz on sandwich-complexes leads for ferrocene and dibenzenechromium to remarkable agreements with SCF-calculations of Shustorovich and Dyatkina as far as bonding MO's are concerned.The overlap integrals obtained for complexes of the type (C _nH_n)₂Me (n=4–8) from simplified SCF wave functions turn out to present fairly favourable overlap conditions even for n=7 and 8.The participation of f-orbitals which should in principle be possible in the bonds of the hypothetical complex (C ₈H₈)₂U is discussed.

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Résumé La méthode d'approximation simple LCAO-MO de Wolfsberg et Helmholz, appliquée aux complexes sandwich, donne, pour les orbitales moléculaires liantes du ferrocène et du dibenzènechrome, des résultats en bon accord avec des calculations SCF de Shustorovich et Dyatkina.D'après les intégrales de recouvrement, obtenus pour des complexes (C _nH_n)₂Me (n=4–8) en utilisant les fonctions ondulatoires SCF simplifiées on trouve des conditions de recouvrement relativement favorables même dans les cas n=7 et 8.On discute la participation d'orbitales f qui, en principe, est possible dans la liaison du complexe hypothétique (C ₈H₈)₂U.

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Herrn Prof. Dr. C. J. Ballhausen sei herzlich gedankt für wertvolle Anregungen und Diskussionen sowie für die Durchsicht des Manuskripts. — Herr Dr. J. Voitländer stellte uns freundlicherweise noch unveröffentlichte Ergebnisse zur Verfügung. — Der Deutsche Akademische Austauschdienst ermöglichte die Arbeit durch die Vermittlung eines- NATO-Forschungsstipendiums.     

Nonaqueous electrochromatography on continuous bed columns of sol–gel bonded large-pore C18 material: separation of retinyl esters

A nonaqueous electrochromatographic reversed-phase separation method for retinyl esters using continuous bed columns has been developed. The packing material 7 μm Nucleosil 4000 Å C₁₈ was sol–gel bonded in 180 μm I.D. capillaries. The mobile phase used was 2.5 mM lithium acetate in N,N-dimethylformamide–acetonitrile–methanol (2+7+1, v/v). At 350 V/cm and 30°C, this mobile phase composition gave rise to an electroosmotic flow of 1 mm/s. No Joule heating nor bubble formation were observed even at 625 V/cm (17 μA). With a 36 cm L_eff column complete separation of the commercially available and synthesized standards (all-trans-retinyl acetate, palmitate, heptadecanoate, stearate, oleoate, and linoleoate) was obtained within 10 min. The within-day and between-day variations of retention times of all-trans-retinyl palmitate were <0.3% relative standard deviation (RSD) (n=3) and <2% RSD (n=6), respectively. The within-day and between-day variations of peak areas were both <2% (both n=3). The columns were used for more than 1 month without degradation. Liver extracts from arctic seal were analyzed.     

Polarographische Bestimmung kleiner Wolframmengen

Zusammenfassung Sehr kleine Wolframkonzentrationen von etwa 0,1–20 g/ml werden am besten in Grundlösungen mit 9–10 m PerchlorsÄure + 0,6–0,7 m WeinsÄure polarographisch bestimmt. Für höhere Konzentrationen von etwa 20–100 g/ml sind Lösungen mit 9–10 m SalzsÄure + 0,3 m WeinsÄure (oder 0,1 m CitronensÄure) + 0,01% Gelatine vorzuziehen.

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Summary For the determination of very small concentrations of tungsten (0.1 to 20 g/ml) solutions with 9–10 M perchloric + 0.6–0.7 M tartaric acid are especially suitable. The determination of higher concentrations (20–100 g/ml) should be preferably performed in solutions with 9–10 M hydrochloric + 0.3 M tartaric acid (or 0.1 M citric acid) + 0.01% gelatin.

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Herrn Prof. Dr., Dr. h.c. Dr. h.c. Dr. h.c. Wilhelm Klemm zum 70. Geburtstag gewidmet.     

Photometrische Bestimmung von Anionen mit Chloranils?ure I

Zusammenfassung Es wird eine übersicht über die Anwendbarkeit der ChloranilsÄure für photometrische Bestimmungen von Kationen und Anionen gegeben. ChloranilsÄurelösungen sind nur begrenzt haltbar; im allgemeinen sind die Extinktionen solcher Lösungen über mindestens 5 Std konstant. Es werden die Dissoziationskonstanten der ChloranilsÄure bestimmt und zwar in wÄ\rigen Lösungen und in wÄ\rig-alkoholischen Lösungen, die 41,6 Gew.-% Äthanol enthalten. In rein wÄ\rigen Lösungen wird für T=25 C und I=1,0 gefunden: K ₁=1 · 10^–1 und K ₂=2,3 · 10^–3. In wÄ\rig-alkoholischen Lösungen wird für T=25 C und I=0,1 gefunden K ₁=4 · 10^–2 und K ₂=1,56 · 10^–4.

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Summary A report is given on the applicability of chloranilic acid for photometric determinations of cations and anions. Solutions of chloranilic acid are of limited stability only; the extinctions of these solutions remain constant for at least 5 hours. The dissociation constants of chloranilic acid have been determined in aqueous and in aqueous-alcoholic solutions containing 41.6% (w/w) ethanol. The following results have been obtained: K ₁=1 · 10^–1 and K ₂=2,3 · 10^–3 for purely aqueous solutions (T=25 C; I=1.0); K ₁=4 · 10^–2 and K ₂=1.56 · 10^–4 for aqueous-alcoholic solutions (T=25 C; I=0.1).

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Herrn Prof. Dr., Dr. h. c. W. Klemm zum 70. Geburtstag gewidmet.

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Die Arbeit wurde durch die Deutsche Forschungsgemeinschaft und den Fonds der Chemie durch Sachbeihilfen gefördert.     

Space-time chaos in reactions of NADH with atmospheric oxygen in the presence of copper(II) complexes

In the oxidation of aqueous solutions of NADH by atmospheric oxygen in the presence of certain copper(II) compounds, an irregularly oscillating timewise change has been observed in the potential of a point platinum electrode (PPE), relative to either a silver chloride electrode or a second PPE located in the same solution. Phase portraits have been constructed on the basis of experimental data for all of the systems that have been investigated. It has been shown that the existence of chaotic oscillations, and also the form of the phase portrait of the systems, depend on the magnitude of the redox potential of the CuL²⁺/CuL⁺ pair. For compounds with E₀=0.60–0.64 V, the phase portrait has the form of a screw-type chaos, which then changes over to Lorentz-type chaos. Only for this group of complexes is chaotic behavior observed when the solution is stirred. For compounds with E₀=0.15–0.41 V, screw-type chaos is observed; and for compounds with E₀<0, no chaotic behavior has been detected.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 26, No. 2, pp. 175–184, March–April, 1990.     

Chelatometrie. VI

Zusammenfassung Mit 0,1 m Äthylendiamintetraessigsäure (EDTA) lassen sich in Lösungen, die viel Natriumacetat und Ammoniumrhodanid enthalten, bis zu 150 mg Kupfer(II)-Ionen gegen den Redoxindicator Variaminblau B-Base titrieren. Der optimale Arbeitsbereich liegt bei p_H 5,5. Eisen(III) stört nicht, wenn es mit Ammoniumfluorid getarnt wird. Nicht zu große Erdalkalikonzentrationen sind ohne Einfluß auf das Titrationsergebnis.Die inverse Titration von EDTA mit Kupfer(II)-chloridmaßlösung ermöglicht die indirekte Bestimmung einiger Metall-Ionen, die vorher bei p_H 4,5–6,0 mit überschüssiger EDTA umgesetzt werden.Ferner werden weitere Untersuchungsergebnisse zur Verwendung des Kupfer(II)/Kupfer(I)-Redoxsystems in der Chelatometrie mitgeteilt.Über direkte Titrationen von Zink- und Bleisalzlösungen mit EDTA, die in Gegenwart von etwas Kupfer(II)-rhodanid und von Variaminblau B-Base bei p_H 5,5 möglich sind, soll später berichtet werden.Mitteilung V dieser Reihe: diese Z. 140, 241 (1956).Herrn Prof. Dr. L. Erdey, Budapest, sei vielmals für die Überlassung von Variaminblau B-Base gedankt. Dem freundlichen Entgegenkommen der Badischen Anilin- & Sodafabrik A.G., Ludwigshafen a. Rhein, verdanke ich das Trilon BS. Herrn W. Johannsen, Leiter des Laboratoriums der Metallhütte Mark A. G., bin ich für das dieser Arbeit entgegengebrachte Interesse verpflichtet.     

Structures, phase transitions and microwave dielectric properties of the 6H perovskites Ba3BSb2O9, B=Mg, Ca, Sr, Ba

We present a complete temperature-composition phase diagram for Ba₃BSb₂O₉, B=Mg, Ca, Sr, Ba, along with their electrical behavior as a function of B. These compounds have long been recognized as 6H-type perovskites, but (with the exception of B=Mg) their exact structures and properties were unknown due to their low symmetries, temperature-dependent phase transitions, and difficulties in synthesizing pure samples. The full range of possible space group symmetries is observed, from ideal hexagonal P6₃/mmc to monoclinic C2/c to triclinic . Direct second-order transitions between these phases are plausible according to group theory, and no evidence was seen for any further intermediate phases. The phase diagram with respect to temperature and the effective ionic radius of B is remarkably symmetrical for B=Mg, Ca, and Sr. For B=Ba, a first-order phase transition to a locally distorted phase allows a metastable hexagonal phase to persist to lower temperatures than expected before decomposing around 600 K. Electrical measurements revealed that dielectric permittivity corrected for porosity does not change significantly as a function of B and is in a good agreement with the values predicted by the Clausius-Mossotti equation.     

Eine Methode zur schnellen Bestimmung von Bromid, sowie von Bromid und Jodid nebeneinander in Anwesenheit von Chlorid

Zusammenfassung Bromid reagiert mit Hypochlorit bei p _h 10–11 quantitativ nach der Gleichung: ClO^–+Br^–=Cl^–+BrO^–. Auf Grund dieser Reaktion kann Bromid einfach und schnell bestimmt werden. Die Arbeitsweise entspricht der der früher beschriebenen Methode der Jodidbestimmung mit der Abänderung, daß das in der Lösung vorhandene Hypobromit vor der Rücktitration des Hypochloritüberschusses mittels Natriumphenolat selektiv reduziert wird.Zur Bestimmung von Bromid und Jodid nebeneinander stellt man in einer Probe nach der vorstehenden Arbeitsweise die Summe der beiden Halogene fest. In einer zweiten Probe ermittelt man nach derselben Methode, jedoch ohne Phenolatzusatz, das Jodid allein. Der Bromidgehalt ergibt sich dann aus der Differenz.Ist auch Chlorid neben den beiden anderen Halogenen zu bestimmen, so wird in einer dritten Probe die argentometrische Titration zur Bestimmung des Gesamthalogengehaltes durchgeführt.Ich fühle mich verpflichtet, Herrn Professor Dr. Johann Proszt, dem Leiter des Institutes, meinen aufrichtigsten Dank auch an dieser Stelle auszusprechen für die Liebenswürdigkeit, womit er meine Versuche ermöglicht hat.