Control of the morphology and composition of yttrium fluoride via a salt-assisted hydrothermal method

Yttrium fluoride such as Na(Y1.5Na0.5)F-6 and alpha-NaYF4; YF3 has been successfully synthesized via a salt-assisted hydrothermal method in the presence of sodium nitrate. The morphology and chemical composition of the as-obtained products can be controlled by monitoring the reaction parameters inclusive of the time-zero concentration of salt solution, reaction temperature and time. The as-prepared products cover Na(Y1.5Na0.5)F-6, alpha-NaYF4 and YF3, while the corresponding morphology changes from spherical aggregation to octahedron, which were characterized by XRD, SEM, and TEM. Moreover, LnF(3) (Ln = La, Nd, Eu, Gd) can also be synthesized using the same method. Further studies reveal that the morphology and composition of the as-synthesized lanthanide fluoride can be determined mainly by the ionic radius of rare earth and the concentration of NaNO3. It is emphasized that the sodium nitrate plays an important role in such control of the differentiated products. Apart from these findings, the photoluminescent properties of Eu3+:YF3 octahedral crystals are further investigated.