Thermal analysis of lanthanum hydroxide

Lanthanum oxide (La2O3) is of great interest as catalyst material. When La2O3 particles are prepared from lanthanum hydroxide (La(OH)3) by thermal processes under air, various oxycarbonate phases are formed which are resistant to thermal hydroxylation. This phenomenon has not yet been extensively investigated, even though oxycarbonate phases at the particle surfaces cause a change in lanthanum oxide’s catalytic activity. The carbonate phases formed cannot be detected by means of XRD or REM-EDX investigations due to their detection limits. Thermal analysis, particularly TG-FT-IR, allows not only for the detection of the carbonate phases in La(OH)3, but also for the tracking of the entire dehydration process from La(OH)3 via LaOOH to La2O3 as well as the correct interpretation of mass changes during the thermal transformations. Pursuant to the investigations here carried out, it was determined that carbonate-free lanthanum hydroxide compounds can only be prepared and stored in a CO2-free protective gas atmosphere (e.g., argon).