Phase transformation of mixed lanthanide oxides in an aqueous solution

Abstract

were synthesized at 1000 °C for 4 h, followed by characterization using X-ray diffraction (XRD) techniques before and after contact with an aqueous solution at neutral pH and 60 °C for 4 weeks. The XRD patterns of the mixed oxides confirmed a tendency to form oxide or hydroxide solid solutions depending on their mixing ratios. A complete solid solution of (La,Nd) 2 O 3 underwent transformation to (La,Nd)(OH) 3 , while the separated La 2 O 3 + Nd 2 O 3 were converted to La(OH) 3 + Nd(OH) 3 . A similar trend was observed for (La,Eu) 2 O 3 , while (Eu,Tm) 2 O 3 resulted in separate Eu(OH) 3 and Tm 2 O 3 after contact with an aqueous solution because of the resistance of Tm 2 O 3 to the hydration reaction. The formation of ternary oxide solid solutions and their transformation in an aqueous solution could be satisfactorily explained by the trends observed for binary mixed lanthanides.