A study of nonstoichiometric oxides in the Ln-Ni-O (Ln=La, Pr, Nd) system

Abstract

The non-stoichiometric compositions Ln2-xNiO4-3x/2+ (Ln=La, Pr, Nd, 0x0,4) were obtained using coprecipitation method from nitrates solutions by K2CO3 followed by calcination of the obtained blend at 950С. According to X-ray phase analysis compositions in the range La2NiO4.17 -La1.6NiO3.63 are monophase and crystallize in tetragonal symmetry K2NiF4, space group I4/mmm. Nd2-xNiO4-y and Pr2-xNiO4-y in the range 0x0,2 are monophase and have orthorombic and monoclinic(correspodingly) distorted K2NiF4 structure. Samples with 0,2<x0,4 are polyphase and contain Ln2NiO4 (Ln=Pr, Nd), NiO and rare earth oxides. Electrical conductivity of obtained samples has semiconducting behavior and it is strongly depended to nonstoichiometric oxygen content. Results and discussionThe combined thermogravimetric and IRspectroscopic studies showed that the Experimental partTo prepare solutions, we used La, Ni and Ca nitrates ("pure for analysis") as starting substances. A trilonometric analysis of the metal content in the solutions was performed