Raman and infrared spectroscopic studies of (NaF-KF)-K2MoO4-B2O3 melts andthe mechanism of electrodeposition of molybdenum

The structure of molybdenum and boron species in the ternary system (NaF-KF )-K2MoO4-B2O3 and the quasi-binaries (NaF-KF)-K2MoO4, (NaF-KF)-B2O3, K2MoO4 -B2O3 were investigated by Raman (melts and solids) and IR (solids) spectro scopy. The Raman spectra of the melts show the Mo-containing species MoO42- only in K2MoO4-oxofluoride melts. When B2O3 is added the B2O3 network is b roken down and anions of the BO3F4- and BO2 F-2(3-) types may form. These a nions may play a crucial role in the MoO42- reduction mechanism by complexi ng O2- ions liberated when molybdenum metal is depositing. The spectra of t he fluoride-containing melts and solids do not show hetero-poly anions or o xide bridging molybdenum complexes. Such complexes have been suggested in t he literature in order to explain the electroreduction of molybdate.