One-step surfactant-free synthesis of Eu3+-activated NaTb(MoO4)2 microcrystals with controllable shape and their multicolor luminescence properties

Abstract

Uniform NaTb(MoO₄)₂ (NTM) microcrystals with controllable morphologies were synthesized via a facile one-step hydrothermal route without employing any templates or surfactants. Diverse morphologies were achieved by manipulating the crystal growth environment; particularly, by increasing the amount of Na₂MoO₄, uniform and well-defined NTM microcrystals with bipyramid, truncated bipyramid, quasi-cube and thin plate shapes were achieved, and the mechanism of this variation was due to the strong electrostatic interaction between MoO₄²⁻ and Tb³⁺/Na⁺. In addition, multicolor emissions (green → yellow → red) of NTM:Eu³⁺ phosphors were obtained by merely adjusting the Eu³⁺ doping content, which resulted from the efficient energy transfer (ET) from MoO₄²⁻ to Tb³⁺ and then to Eu³⁺. Further research revealed that the efficient ET mechanism (Tb³⁺ → Eu³⁺) was dominated by the dipole–quadrupole interaction. It was found that the larger crystal shape/size could greatly enhance their luminescence properties, resulting from their high crystallinity and few defects on the crystal surfaces. The as-synthesized phosphors might be potentially applied in multicolor lighting and displays.