Synthesis of anhydrous lanthanum acetate. Analysis of it’s structural, thermal and electronic properties

Abstract

Acetate complexes of rare earth elements are extensively studied compounds known for their diverse properties and potential applications and lanthanum acetate hydrate is commercially available. In this work, a powdered anhydrous lanthanum acetate (La(CH3COO)3) sample was prepared by dissolving lanthanum oxide (La2O3) in an excess of acetic acid (CH3COOH) and distilled water (H2O), followed by direct evaporation at 150 °C. The decomposition of La(CH3COO)3 was studied, showing initiation around 300 °C and conclusion at ≥700 °C, with four distinct thermal events (I–IV) of mass loss. Gas phase identification revealed acetone and carbon dioxide as decomposition products, indicating pyrolytic decarboxylation. The final thermal effect (IV) is linked to the decomposition of La2O2CO3 to La2O3. The DFT refinement of atomic coordinates of hydrogen atoms, which were unavailable from experiment, was successfully performed. Obtained structural data was checked using vibrational spectroscopy method. The calculated electronic band structure of La(CH3COO)3 indicates it as an indirect wide band gap material with values of direct transition close to indirect. The optical bandgap is found to be 5.49 eV, suggesting that the charge transfer in La(CH3COO)3 can be optically activated with wavelengths shorter than 226 nm, which falls within the deep UV (DUV) region.