Simultaneous morphology, phase modulation and luminescence enhancement in α/β-NaYF₄: Yb³⁺, Er³⁺, Gd³⁺ microcrystals

In this paper, α/β-NaYF₄: Yb³⁺, Er³⁺, Gd³⁺ microcrystals with multiform morphologies were successfully fabricated through hydrothermal approach. The crystal phase of the product can be regulated from cubic to hexagonal, and the overall morphology can be modulated from spherical to rod-like by precisely increasing the pH value of reaction solution. Morphology-dependent luminescence spectra show that the emission intensity gradually increases as the morphology transforms from microsphere to microrod, and the luminescence color changes from green to yellow-green. After tri-doping with 9 mol% Gd³⁺ ions, the luminescence intensity of cubic and hexagonal NaYF₄: Yb³⁺, Er³⁺ microcrystals is increased by 2 and 5 times, respectively, and the luminescence brightness is also significantly enhanced. The as-prepared α/β-NaYF₄: Yb³⁺, Er³⁺, Gd³⁺ microcrystals with excellent luminescence performance may have potential applications in display and lighting device fields.