Synthesis of spherical aggregates of leaf-like YPO4 particles via hydrolysis of tri-n-butylphosphate

Spherical aggregates of leaf-like YPO4 particles have been prepared by the reactions of tri-n-butylphosphate [PO(OC4H9)3, TBP] with the acidic Y(NO3)3 aqueous solution in an autoclave at 180°C. The products of the reactions for 1, 3 and 6 h consisted of an intermediate exhibiting an intense X-ray diffraction line at d ≈ 1.28 nm, while those of reactions for 12–48 h were pure YPO4. The products of the reactions for 8 and 8.5 h were mixtures of the intermediate and YPO4. YPO4 formation thus seems to proceed via the formation of the intermediate. Since the intermediate seems to be Y[PO2(OC4H9)2]3, it is likely that TBP was hydrolyzed to form PO2(OC4H9)2− ions, which then reacted with Y3+ ions to form the solid intermediate, Y[PO2(OC4H9)2]3. Scanning electron microscopy (SEM) revealed the corresponding morphological change from the belt-like products to spherical aggregates of leaf-like particles, indicating that the solid intermediate Y[PO2(OC4H9)2]3 was hydrolyzed to form leaf-like YPO4 particles.