Study of the formation of perovskite type lanthanum ruthenates by heating their hydrous precursor

Abstract

Emanation thermal analysis (ETA), differential thermal analysis (DTA), thermogravimetry (TG), evolved gas analysis with mass spectrometric detection (EGA-MS), and X-ray diffraction (XRD) were used to investigate the formation of perovskite type lanthanum ruthenates on heating their hydroxide precursor in argon from 20 to 1200 ◦C. The co-precipitated lanthanum–ruthenium mixed hydroxide containing a small amount of carbonates was used as a precursor. The mass loss corresponding to the release of water and CO2 from the precursor was determined by TG and EGA (MS), respectively. The ETA characterized the exposure of sample surface after release of water and CO2, as well as microstructure development corresponding to the crystallization and structure ordering of LaRuO3 and La3.5Ru4.0O13 perovskite phases. The obtained information on formation of phases and their transformation is useful for optimizing their synthesis protocols for achieving the desired physical properties, and to estimate the thermal stability of these materials to be used as catalysts