High temperature orthorhombic/tetragonal transition and oxygen content of Pr2-xNdxNiO4+δ (x= 0, 0.3, 1, 1.7 and 2) solid solutions

Abstract

Single-phase Ruddlesden popper of Pr2-xNdxNiO4þδ with x ¼ 0, 0.3, 1, 1.7 and 2, were successfully synthesized by a sol-gel route. The thermal behavior of the prepared samples has been studied at the temperature range 25–800 C in air using Differential Thermal Analysis (DTA), Thermogravimetric Analysis (TGA) and High Temperature X-ray diffraction (HT-XRD). These results show that Pr2-xNdxNiO4þδ (PNNO) solid solutions undergo a transition from an orthorhombic phase to a tetragonal one at temperatures depending of Nd content. Samples with high content of Pr (x ¼ 0 and 0.3) decompose to a mixture of phases after heated up to 800 C. This happens due to the partial oxidation of Pr3þ leading to segregation of secondary phases. Thermal stability below 800 C was observed for PNNO samples with x ¼ 1, 1.7 and 2.