The preparation of the single-phase perovskite LaNiO3

There is growing use of the perovskite type mixed metal oxide materials. A host of useful properties have been well known for some time. They exhibit piezoelectricity, pyroelectricity, ferroelectricity, high temperature superconductivity and also display catalytic activity. It is, thus, important to investigate preparative routes that can yield single-phase perovskite materials free of any extraneous metal oxides. This work reports the preparation of a single-phase perovskite LaNiO3 synthesised by co-precipitation from metal salt solutions using various organic precipitating reagents. A single perovskite phase was realised at low processing temperatures (800 degrees C) and this was stable to 1000 degrees C. At temperatures of 1000 degrees C and above LaNi2O4 and other unidentified mixed oxide systems were observed. Evaporation and sol-gel routes were also explored but these resulted in poor homogeneity and complex multiphase oxide systems. Phase analysis was performed using powder X-ray diffraction (PXRD). Diffractograms were Rietveld refined using the trigonal space group, R-3 C, and crystallographic parameters for the oxide system are reported. Differential scanning calorimetry (DSC) was used to probe the solid-state reaction of the precipitated metal products and scanning electron microscopy (SEM) was used to examine the morphology of the resulting particles. (C) 1999 Elsevier Science S.A. All rights reserved.