AN INVESTIGATION OF THE HIGH-TEMPERATURE REACTION OF THE ALKALI-METAL METAVANADATES MVO3 (M=NA,K) WITH THE LANTHANIDE OXIDES LN2O3 (LN=ND,ER)

The changes occurring in the dielectric constant of an alkali metal metavanadate after it has been treated at high temperatures with a small percentage of a lanthanide oxide were previously ascribed to solid solution formation [R.T. Patil, N.B. Patil, A.P. Kashid and S.H. Shavan, Mat. Res Bull. 25, 57 (1990).]. Analysis of the products obtained by means of Raman spectroscopy, X-ray powder diffraction, SEM and EDX-analysis, however, revealed that a small amount of the lanthanide orthovanadate is formed in the metavanadate mass. The reaction that takes place could be described by the following equation: 2MVO3 + Ln2O3 --> DELTA 2LnVO4 + M2O. With stoichiometric amounts of the reagents under vacuum conditions full conversion occurs to the lanthanide orthovanadate.