Preparation of undoped and Tb3+-doped fluorescent HfO2 spherical particles

Undoped and Tb3+-doped HfO2 spherical particles were prepared by a sol-gel method, by using hafnium tetra-l-butoxide (Hf(O-t-C4H9)(4))) as a precursor of hafnium dioxide, SPAN85 (R) as a surfactant, mixed solvent of C2H5OH and n-C4H9OH, and H2O, followed by investigation of their structural and optical properties. Spherical particles with good morphology and comparatively high dispersibility were obtained from solutions with the molar ratio SPAN85 (R):H2O = 1:8-17.5, their sizes being 0.2-5 mu m in diameter. Particles became small and aggregated when the molar ratio of H2O was more than 17.5, but became large when it was less than 8. Spherical particles heat treated at 400 degrees C or below were amorphous, and those heat treated at 600 degrees C or above were crystallized. Tb3+-doped HfO2 spherical particles showed green luminescence due to the D-5(4)-> F-7(J) (J = 6, 5, 4, 3) transitions of the Tb3+ ion, and relatively strong luminescence was observed both in dried gel particles and particles heat treated at 1000 degrees C. These Tb3+-doped HfO2 Spherical particles can be expected for new optical materials.