Synthesis and Phase Composition of Lanthanide Phosphate Nanoparticles LnPO4 (Ln=La, Gd, Tb, Dy, Y) and Solid Solutions for Fiber Coatings

Rare earth phosphates with rare earths of Gd, Tb, and Dy can form either monazite or xenotime. Hydrated lanthanide phosphate precursors to monazite and xenotime were made in aqueous solution. The particles were formed by adding dilute phosphoric acid (H3PO4) to either; (a) lanthanide citrate (Ln-Cit) or (b) lanthanide nitrate (LnNO(3)) [Ln=La, Gd, Tb, Dy, and Y] solutions followed by altering the pH from similar to 1 to similar to 10 with ammonium hydroxide. Precursor particle size and morphology was characterized by scanning electron microscopy, (SEM) and weight loss was characterized by thermogravimetric analysis (TGA). The phase presence at temperature was determined by differential thermal analysis (DTA) and X-ray diffraction. The influence of precursor preparation method on the presence of either monazite or xenotime after heat treatment is discussed.