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Die Synthese von Boraziten mit Hilfe Chemischer Transportreaktionen

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Published in Journal of Physics and Chemistry of Solids. 1965, vol. 26, no. 6, p. 973-988
Abstract A new method of prepg. boracites (M3B7O13X, M = a bivalent metal, X = Cl, Br, or I)is described. The process takes place in sealed quartz tubes with the aid of chem. transport reactions and permitted the prepn. of the Cr-Br-, Cr-I-, Cu-Cl-, and Cu-Br-boracites. In most cases, single crystals were obtained. The transport of MO to the growing boracite crystal can be achieved by the reaction MO + 2HX(g) = MX2(g) + H2O(g), or MO + X2(g) = MX2(g) + 0.5O2, and that of CuO via the cuprous halides. B2O3 is transported preferably via a liquid film to the growing crystal. At high HX and H2O pressure, the formation of boracite based on the transport of B2O3 via the gas phase was observed. Thermodynamic estns. of the transport reaction equil. of MO and B2O3 were made. The results were discussed with respect to the observed crystn. properties of the different boracites. With transport of MeO and B2O3 via the gas phase, some transition metal borates were obtained. In an orienting expt., Mg-Cl boracite was prepd. at .apprx.150 Deg to 180 Deg by transport reactions in aq. soln. The lattice parameters and a,b-transition temps. of all the boracites were detd. On Co-I boracite, an alexandrite effect is observed. The Fe-Cl-, Fe-Br-, Ni-Cl-, Ni-Br-, Ni-I, and Cu-Br boracites show thermochroism.
Keywords Chemical transport reactionsCrystal growthBoracites
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SCHMID, Hans. Die Synthese von Boraziten mit Hilfe Chemischer Transportreaktionen. In: Journal of Physics and Chemistry of Solids, 1965, vol. 26, n° 6, p. 973-988. https://archive-ouverte.unige.ch/unige:32488

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