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  • 1
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The dielectrical properties of glass ceramics derived from SrO–B2O3–Al2O3–TiO2 glasses are improved by doping the starting material with Nb2O5 and judicious choice of heat treatment conditions. In order to understand this effect the local environment of the niobium ions is studied by EXAFS (extended X-ray absorption fine structure) investigations at the Nb-K edge. For comparison purposes Ti-K and Sr-K EXAFS spectra have also been measured. The experiments suggest that the niobium ions are incorporated onto titanium sites in the crystalline SrTiO3 phase formed during the thermal treatment.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 435 (1977), S. 61-68 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Rearrangement of Alkyl Groups in N-phosphorylated AlkoxyphosphazenesWith diazomethane the tetrachloride as well as the tetraethylester of imidodiphosphoric acid form mixtures of O- and N-methyl derivatives. However diazoethane reacts with the tetraethyl ester only by O-ethylation yielding triethoxyphosphazene phosphoryl diethyl ester. Trichlorophosphazene phosphoryl dichloride reacts with methyl or ethyl alcohol in the molar ratio of 1:1 forming alkoxydichlorophosphazene phosphoryl dichlorides. The rearrangement of the O-alkyl derivatives to the N-alkyl isomers has been proved by 1H- and 31P-n.m.r. spectroscopy. In the case of triethoxyphosphazene phosphoryl diethyl ester it only occurs in the presence of ethyl iodide as catalyst.
    Notes: Sowohl das Tetrachlorid als auch der Tetraäthylester der Imidodiphosphorsäure bilden mit Diazomethan Gemische der O- und N-Methylderivate. Diazoäthan jedoch reagiert mit dem Tetraäthylester ausschließlich unter O-Äthylierung zum Triäthoxyphosphazenphosphoryldiäthylester. Trichlorphosphazenphosphoryldichlorid reagiert mit Methanol bzw. Äthanol im Molverhältnis 1:1 zu den Alkoxydichlorphosphazenphosphoryldichloriden. Die Umlagerung der O-Alkylderivate in die N-Alkylisomeren wurde mittels 1H- und 31P-NMR-Spektroskopie bewiesen. Im Falle des Triäthoxyphosphazenphosphoryldiäthylesters erfolgt sie nur in Gegenwart von Äthyljodid als Katalysator.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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