Preparation and Properties of Lanthanide Phosphates
Lanthanide phosphates are known as slightly soluble salts with their solubility products ranging from 10-25 to 10-27. These phosphates can be obtained a) by precipitation from aqueous solutions of their salts using, for example, sodium or ammonium phosphates or b) by crystallization from boiling phosphoric acid solution. Application of crystallization in highly acidic solution instead of precipitation method yields highly crystalline solids of the composition of LnPO4.H2O (Ln: La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu and Y). This paper presents the effect of the acidity of the solution used for the crystallization process on crystallinity and morphology of EuPO4.H2O obtained: the higher the acidity of the solution the larger the crystals obtained. The morphology of the crystals changed from sphere-like particles crystallized in 2M H3PO4 to large hexagonal rods formed 2M H3PO4 with additional 0.4 M of HCl or HNO3.
Panjian Li, Kai Zhang and Clifford W. Colwell, Jr.
R. Kijkowska and R. Z. LeGeros, "Preparation and Properties of Lanthanide Phosphates", Key Engineering Materials, Vols. 284-286, pp. 79-82, 2005