Low-temperature flux growth of sulfates, molybdates, and tungstates of Ca, Sr, and Ba and investigation of doping with $Mn^{6+}$

Romanyuk, Y.E. and Ehrentraut, D. and Pollnau, M. and Garcia-Revilla, S. and Valiente, R. (2004) Low-temperature flux growth of sulfates, molybdates, and tungstates of Ca, Sr, and Ba and investigation of doping with $Mn^{6+}$ . Applied physics A: Materials science & processing, 79 (3). pp. 613-618. ISSN 0947-8396

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Abstract:	The growth of undoped and $Mn^{6+}$ -doped molybdates and tungstates of alkali-earth metals and BaSO4 has been investigated. Single crystals were grown by the flux method within the temperature range of 600–475 °C, using the ternary NaCl–KCl–CsCl solvent. Sizes of undoped crystals increase within the series tungstates < molybdates < sulfate and, depending on the cation, within the series $Ca^{2+}Sr^{2+} < Ba^{2+}$ . The $Mn^{6+}$ ion tends to be reduced to $Mn^{5+}/Mn^{4+}$ with time in the chloride solution, but can be partly stabilized by the addition of alkali-metal carbonates or hydroxides. The incorporation of $Mn^{6+}$ is governed by the coordination of the $MnO^{2-}_{4}$ tetrahedron in the crystal. No significant doping was found for Ca and Sr compounds and only small amounts of Mn6+ were incorporated into $BaMoO{_4}$ and ${BaWO}_4$ . Crystals with orthorhombic space group Pnma such as ${BaSO}_4$ exhibit significantly higher doping levels. The $Mn^{6+}$ distribution in each crystal varies due to manganese reduction with growth time. Temperature-, time-, and concentration-dependent spectroscopy of ${BaSO}_4$ : $Mn^{6+}$ was performed.
Item Type:	Article
Copyright:	© 2004 Springer
Faculty:	Electrical Engineering, Mathematics and Computer Science (EEMCS)
Link to this item:	http://purl.utwente.nl/publications/61941
Official URL:	http://dx.doi.org/10.1007/s00339-004-2555-8
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