Thermal stability of rare-earth nickelates. Part II: hole and electron doped RNiO3 (R=La,Nd) perovskites

Hole and electron doped RNiO3 nickelates have been synthesized by partially replacing the rare earths by alkali-earth or thorium cations, respectively, in samples of composition R0.9A0.1NiO3 (R = La, Nd; A Ca, Sr, Th), and characterized by X-ray powder diffraction and thermal analysis under reducing conditions (H2/N2). The thermograms show two consecutive reduction processes, with formation of intermediate Ni(II) phases, giving finally R2O3 + AO + Ni mixtures. The variation of the reduction temperatures upon the nature of the R and A cations has been correlated with the basicity of the different cations, as well as with the stability of the perovskite structure. (authors). 8 refs., 3 figs