Influence of Zr4+ doping impurity on crystal phase and upconversion luminescence of Er3+/Yb3+ codoped NaYF4 microcrystals

Abstract

Er3+/Yb3+ codoped NaYF4 microcrystals were prepared via a facile hydrothermal approach assisted with oleic acid. The cubic-to-hexagonal phase transition and enhancement of up-conversion luminescence of Er3+ ions were simultaneously achieved by the gradual addition of Zr4+ ions in the reaction system. X-ray diffraction and SEM results indicated that the introduction of Zr4+ ions could remarkably accelerate the cubic-to-hexagonal phase transition process and pure hexagonal NaYF4 microcrystals were obtained, when Zr4+ mole fraction reached 5%. Strong green and red up-conversion luminescence of Er3+ ions was observed and the up-conversion intensity increased gradually with the addition of Zr4+ ions.