Controllable hydrothermal synthesis and morphology evolution of Zn4B6O13:Tb/Eu phosphors with tunable luminescent properties

A series of Tb, Eu single or co-doped Zn₄B₆O₁₃ phosphors with tetrahedral morphology were synthesized by facile hydrothermal method. The influences of reaction temperature and the pH value of the reaction system on the structures and compositions of product were also investigated, in which four kinds of zinc borates with different structures and compositions (Zn₄B₂O₇·H₂O, Zn₄B₆O₁₃, Zn(H₂O)B₂O₄·0.12H₂O, and H(Zn₆O₂(BO₃)₃)) were obtained. A possible growth mechanism of tetrahedral morphology of Zn₄B₆O₁₃ has been proposed according to reaction time. The obtained samples were characterized by XRD, EDS, SEM, TEM, XPS, BET, DR, PL and QY. XPS results indicate that Eu²⁺ and Tb⁴⁺ are present in Tb/Eu co-doped Zn₄B₆O₁₃, which might be generated from charge transfer between Tb³⁺ and Eu³⁺. The PL results shows that Eu³⁺, Tb³⁺ ion single-doped Zn₄B₆O₁₃ microstructure exhibit orange and green emission under ultraviolet excitation, respectively. Compared to Eu³⁺ and Tb³⁺ single doped Zn₄B₆O₁₃ phosphors, the Eu/Tb co-doped Zn₄B₆O₁₃ phosphors showed stronger blue emission of Eu²⁺. These results imply that the tetrahedral morphology of Eu³⁺, Tb³⁺ ion single-doped and Eu^2+/3+/Tb^3+/4+ co-doped Zn₄B₆O₁₃ phosphors have the promise application for nano/micro-optical functional devices.