STRUCTURAL AND MAGNETIC PROPERTIES OF (R0.5A0.5)NIO3 PEROVSKITES (R = GD, YB AND A = CE, TH)

Abstract

Four perovskite compounds with nominal compositions of ( Gd 0.5 Th 0.5) NiO 3, ( Gd 0.5 Ce 0.5) NiO 3, ( Yb 0.5 Th 0.5) NiO 3 and ( Yb 0.5 Ce 0.5) NiO 3 were prepared by a polymeric citrate precursor method. They were either slow-cooled in the furnace or quenched to room temperature. All of them have monoclinic symmetry. Quenched samples have a slightly bigger unit cell volume and longer Ni-O bond length, and a smaller grain size than that of the furnace-cooled compounds. All samples are paramagnetic insulators in the range of 2 K to 300 K. The Th containing compounds have larger tolerance factor and Ni (1)– O (1)– Ni (2) bond angle than that of the Ce containing compounds. No mixed valence of Ce, Th and Ni is observed in these samples.