PREPARATION AND CHARACTERIZATION OF LNPRO(3- A SERIES OF MIXED LANTHANIDE OXIDES(Y) (LN = Y AND LANTHANIDE) )

Citrate gel method has been employed to produce a series of praseodymi um based homogeneous mixed rare-earth oxides, LnPrO(3+y) (Ln = Y and l anthanide ion). The ionic size of Ln determines the crystal structure of the mixed oxides. LnPrO(3+y) and CePrO3+y crystallise in the fluori te structure, whereas the remaining oxides adopt the C-type structure. The crystal structure and the unit cell parameters of the oxides obta ined at 1173 K in static air have been reported. Wet-chemical analysis suggests that the compositions adopting the fluorite structure are no n-stoichiometric, whilst the compositions crystallising in the C-type structure are stoichiometric. The surface area has been measured and t he adsorption-desorption isotherms obtained for the compositions. The BET surface area of the oxides are in the range 1.5 to 3.5 m(2) g(-1) and the isotherms reveal that the oxides are free from porosity. (C) 1 998 Elsevier Science B.V. All rights reserved.