SYNTHESIS AND PHYSICO-CHEMICAL STUDIES OF BINARY RARE EARTH VANADATES

摘要

The Interaction between compounds in ternary systems Ln_2O_3 -M_2CO_3 -V_2O_5(Ln = La,Sm, Gd,Ho,Y:M=Na,K ,Rb)was studied by X-ray diffraction and DTA methods. The starting molar ratios for syntheses were Ln_2O_3:M_2CO_3:V_2O_6=1:3:2(4 for NH_4VO_3) at temperatures (20°-1000°) Transformation features of polyvanadate groups were found to be depended on temperature and heating rate at initial stage (≤450°) as well as on character of starting compounds (V_2O_5 or NH_4VO_3) . All the obtained compounds has glazerite derived structures. They possess the property of H_2O vapors absorbing. The most absorbability was observed for Rb compounds and in this case the amount of absorbed water increased in series of isostructure compounds La-Sm-Gd-Ho(Y).