Determination of chloride and bromide in lead telluride and bismuth telluride systems

Summary An indirect analytical method, based on measurement of silver, for determining chloride and bromide in bismuth and lead tellurides was developed. The samples were dissolved in dilute nitric acid and the halides were separated as the silver salts by strong centrifugation. The excess of silver was directly determined in the sample solution by solvent extraction with dithizone in carbon tetrachloride and by spectrophotometric determination. Suitable conditions for masking interfering elements were established so that a very selective procedure for silver determination was achieved. Chloride and bromide down to 0.01 mole % could be determined. A procedure for determining chloride and bromide in the same sample with no interference from iodide, was also developed.

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Zusammenfassung Ein indirektes, auf der Messung von Silber beruhendes Verfahren zur Bestimmung von Chlorid und Bromid in Wismut- und Bleitelluriden wurde entwickelt. Die Proben werden in verd. Salpetersäure gelöst und die Halogenide als Silbersalze scharf abzentrifugiert. Der Silberüberschuß wird unmittelbar aus dem Filtrat mit Dithizonlösung extrahiert und spektro-photometrisch gemessen. Geeignete Maßnahmen zur Maskierung störender Elemente wurden angegeben, so daß ein sehr selektives Verfahren zur Silberbestimmung vorliegt. Bis zu 0,01 Molprozent Chlorid und Bromid sind noch bestimmbar. Außerdem wurde ein Verfahren zur Chlorid- und Bromidbestimmung in Gegenwart von Jodid entwickelt.

     

Mössbauer investigation of W-type hexaferrite of composition BaZn2−xCoxFe16O27

AbstractPolycrystauine samples of composition BaZn_2–xCo_{x 16}O₂₇ (O2-W undergoes a transition from planar to conical order at 515±5 K.     

Problems in the low-temperature synthesis of 92K Superconducting YBCO

Il Nuovo Cimento D - YBCO with high granulometric perfection and low dispersion can be obtained by a low-temperature reaction (≈800°C) of atomic-scale dispersed powders, produced through...     

Modifications in magnetic anisotropy of M—type strontium hexaferrite crystals by swift heavy ion irradiation.

Using vibrating sample magnetometery (VSM) 50 MeV Li³⁺ ion irradiation effects on magnetic properties of single crystals of SrGa_xIn_yFe_12−(x+y)O₁₉ (where x=0, 5, 7, 9; y=0, 0.8, 1.3, 1.0), are reported. The substitution of Ga and In in strontium hexaferrite crystals decreases the value of magnetization sharply, which is attributed to shifting of collinear magnetic order to a non-collinear one. Reduction of magnetization is also explained to be as a result of the occupation of the crystallographic sites of Fe³⁺ by Ga³⁺ and In³⁺. The Li³⁺ ion irradiation decreases the value of magnetization, irrespective of whether the crystals are Ga–In substituted or unsubstituted crystals of SrFe₁₂O₁₉. The result is interpreted in terms of the occurrence of a paramagnetic doublet in crystals replacing magnetic sextuplet as a result of irradiation. Substitution of Ga–In in Strontium hexaferrite decreases the value of anisotropy constant. Irradiation with Li³⁺ ions increases the values of anisotropy field for both substituted as well as unsubstituted crystals. Substitution with Ga–In also decreases the Curie temperature (T_c) but the irradiation with Li³⁺ ions does not affect the curie temperature of either Ga–In substituted or pure SrFe₁₂O₁₉ crystals.     

Determination of ferrous ion in microsamples of hexagonal ferrites

Summary A sensitive and accurate method is described for determining microgram amounts of ferrous iron associated with a large excess of ferric iron and various bivalent cations, in hexagonal ferrites. Ferrous iron is complexed with bathophenanthroline, extracted into a chloroform-ethanol mixture and spectrophotometrically measured at 540 nm against a 13 v/v chloroform-ethanol mixture. Ferric iron is masked with ammonium dihydrogen phosphate. The analytical conditions are stated for determination of iron(II) in both solvents used for ferrites, viz., hydrochloric and phosphoric acids. Cobalt, copper, and nickel do not interfere if the procedures suggested are used. Ferrous iron down to 0.02% can be determined in samples weighing only a few milligrams.

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Zusammenfassung Eine empfindliche und genaue Methode zur Bestimmung von Mikrogrammengen Eisen(II) in Gegenwart eines großen Überschusses von Eisen(III) und verschiedener zweiwertiger Kationen in hexagonalen Ferriten wurde beschrieben. Eisen(II) wird mit Bathophenanthrolin komplex gebunden, mit einer Chloroform-Äthanol-Mischung extrahiert und bei 540 nm gegen eine Chloroform-Äthanol-Mischung (13 v/v) spektrophotometrisch gemessen. Eisen(III) wird mit NH₄ · H₂PO₄ maskiert. Die Arbeitsbedingungen für die Bestimmung von Eisen(II) in beiden für Ferrite verwendeten Lösungsmitteln — Salzsäure und Phosphorsäure — wurden festgelegt. Co, Cu und Ni stören die empfohlenen Verfahren nicht. Bis zu 0,02% Eisen(II) können in Einwaagen von wenigen Milligramm bestimmt werden.

     

X-ray Topographic Assessment of Defects in Pure and Substituted Hexaferrite Crystals

Results of X-ray diffraction topography, in reflection and transmission scanning geometry, of flux grown single crystals of substituted and unsubstituted hexaferrites bearing composition SrGa_xIn_yFe_12-(x+y)O₁₉ (where x = 0, 5, 7, 9; y = 0, 0.8, 1.3, 1.0) are presented. Diffraction topographs reveal defects like misoriented grains, dislocations, cavities, inclusions, and the strain patterns in these crystals. The unsubstituted hexaferrites exhibit better perfection when compared to the substituted ones. The study is reported to support the results obtained by chemical etching and fractography, besides yielding additional information covering defects.     

Substitutions in YBa2Cu3O7−y and their influence on the magnetic penetration depth,its anisotropy and T c: Muon spin rotation (μSR)

Il Nuovo Cimento D - Deterioration of the superconducting properties of HTC materials, induced by different substitutions, offers a key towards the understanding of the basic HTC interactions....     

Enhanced luminescence of CuCl microcrystals in a organic-inorganic hybrid matrix

γ-CuCl microcrystals were found to segregate in self-assembled (C_nH_2n+1NH₃)₂CuCl₄ hybrid organic-inorganic films deposited by single source thermal ablation. The microcrystals dispersed in the hybrid have sizes of 35 nm, as estimated from X-ray diffraction patterns. The UV photoluminescence efficiency of the embedded microcrystals is more than 100 times higher than that of CuCl films having similar crystallite sizes. PACS 78.67.Bf; 78.55.Hx; 81.07.Pr     

Y-type hexagonal ferrites containing zinc,copper and cadmium: Magnetic properties and cation distribution

A complete magnetic and Mössbauer characterization has been worked out for the Y-type hexaferrites series with (Ba, Sr)₂Me₂Fe₁₂O₂₂ (Me = Zn, Cu, Cd) composition. The data relative to the dependence of the saturation magnetization, anisotropy, Curie temperature and cation distribution on composition and temperature could be logically interpreted as leading to the following conclusions. The magnetic order in Zn₂-Y is characterized by the presence of a “random flip” for which a quantitative model has been developed. The substitution of zinc with cadmium increases the spin flip, which, on the other hand, is reduced or eliminated by substitution of zinc with copper or of barium with strontium: the possibility of partially controlling the value of the saturation magnetization will follow. Also the planar anisotropy of Zn₂-Y can be controlled and finally turned into an axial one by substituting zinc with copper.