Four perovskite compounds with nominal compositions of (Gd0.5Th0.5)NiO3, (Gd0.5Ce0.5)NiO3, (Yb0.5Th0.5)NiO3 and (Yb0.5Ce0.5)NiO3 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.
International Journal of Modern Physics B 21(18-19), pp.3443-3447