SYNTHESIS OF AND APPLICATIONS FOR THE CURIENITE-FRANCEVILLITE MINERAL SERIES
The crystal structures of these minerals are composed of sheets containing dimers of edge sharing V+5O5 pyramids which share oxygen atoms with either one or two uranyl pentagonal bipyramids. Interlayer space in Curienite and Francevillite is populated by Pb and Ba, respectively, as well as water molecules. Although commonly found in nature with variable amounts of Pb and Ba, pure end member compositions have been obtained synthetically. Hydrothermal methods utilizing uranyl pyrovanadate as a starting reagent and the appropriate alkali hydroxide form pure powders of the desired mineral phase after 5 days at 170 ̊C with starting pH<3. Characterized using powder X-ray diffraction, thermogravimetric analysis, and inductively coupled plasma optical emission spectrophotometry, formation enthalpies for these mineral phases will be determined by high temperature oxide melt drop-solution calorimetry. Differences in thermodynamic properties resulting from variable composition will be investigated.