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

Abstract

Yttrium fluoride such as Na(Y_1.5Na_0.5)F₆ and α-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(Y_1.5Na_0.5)F₆, α-NaYF₄ and YF₃, while the corresponding morphology changes from spherical aggregation to octahedron, which were characterized by XRD, SEM, and TEM. Moreover, LnF₃ (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.