Lanthanum oxide (La2O3) is of great interest as catalyst material, but is also used in applications such as the manufacturing of high-quality optical glasses and the production of lanthanum metal. Lanthanum oxide is hygroscopic and can therefore absorb water from its surroundings.
In the case shown here, 643.4 mg of La2O3, contaminated with some carbonate impurities, was weighed in a beaker (volume: 3.5 ml) and heated to 1120°C at 50 K/min in a nitrogen atmosphere. The larger crucible is ideal when measuring samples which are low in contaminant concentration or are not very homogeneous.
The TGA curve reveals several steps. There are some smaller overlapped ones in the temperature range up to 400°C, followed by two well separated steps at 510°C and 705°C (both temperature values correspond to DTG peaks). The total mass loss amounts to 0.43%. Evaluation of the experimental FT-IR spectra identifies water and carbon dioxide as the main gases released.
The plot shows that the dehydration takes place primarily in the first part of the measurement, prior to 400°C; the
formation of carbon dioxide is directly related to the two-step decomposition taking place between 400°C and 800°C.
With the help of this information, the total water loss can be specified as 0.22% (or 1.41 mg) and the amount of CO2 released as 0.21%. (measurement with PERSEUS® STA 449 F1/F3)