Study of interaction between neutral molybdates of rare earths K2CrO4

Interactions in the systems K2CrO4-Ln2(MoO4)3 where Ln=La, Nd have been studied by X-ray phase analysis, thermogravimetry and i.r.-spectroscopy. The interaction begins at 300 deg - 350 deg. Double chromates-molybdates of composition 5K2CrO4xLn2(MoO4)3 and K2CrO4xLn2(MoO4)3 have been obtained. The lattice parameters of these compounds are given, as well as the frequencies of i.r. absorption spectra. Chromates-molybdates of composition K2CrO4xLn2(MoO4)3 have been found to undergo thermal decomposition beginning from 480 deg C due to a redox-process associated with reduction of Cr(6) into Cr(3). The melting temperature of 5K2CrO4xLn2(MoO4)3 chromates-molybdates is 790 deg for La and 820 deg C for Nd. Up to the melting temperature the extent of Cr(6) oxidation in these compounds is stable