SYNTHESIS AND CHARACTERIZATION OF LANTHANUM PHOSPHATE: EFFECT OF STARTING PRECURSOR

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Three powder samples of lanthanum phosphate were prepared via the precipitation method. La₂O₃, LaCL₃, (NH₄)₃PO₄ and H₃PO₄ were used as precursor materials. Chemical and thermal analyses, infrared spectra, X-ray diffraction and particle size techniques were used for characterization. The results of chemical analysis indicated that the three samples are in non-stoichiometric state which attributed to the solubility of the products in the aqueous medium and/or to the partial precipitate of HPO₄^2- and H₂PO₄^- species. The results of infrared spectra exhibited the specific bands of phosphate salts such OH, O=P-O, P-O and O-P-O. A band at 1380 cm^-1 corresponding to PO₂^2- is observed in sample I and II which may due to make complexation species between the phosphates and the metal ions.
The X-ray diffraction indicated the formation of lanthanum phosphates of hexagonal structure of rhabdophane LaPO₄.0.5H₂O. DTA/TGA curves show that the prepared samples remain thermally stable at high temperatures.