Abstract

Lanthanum carbonate particles, which can be used as precursors to lanthanum oxide, have been synthesised from lanthanum nitrate and urea in the presence and absence of ultrasound irradiation. The use of ultrasound irradiation was found to have a remarkable effect on the morphology of the lanthanum carbonate particles formed. Needle-shaped particles were found to be formed in the presence of ultrasound irradiation, whereas spherical carbonate particles were produced in the absence of ultrasound irradiation. Characterization by powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, FT-IR spectroscopy, as well as elemental analysis was carried out on the materials synthesised. The effect of heating on the chemistry and the morphology of the carbonate particles was also investigated. The carbonate particles were found to be completely converted into lanthanum oxide at ca. 725 °C. In the case of the needle-shaped lanthanum carbonate particles, the shape was found to be deformed to a small extent on heating, whereas a larger degree of deformation was observed for the spherical lanthanum carbonate particles.