Influence of microwave hydrothermal reaction factor on the morphology of NaY(MoO4)(2) nano-/micro-structures and luminescence properties of NaY(MoO4)(2):Tb3+

摘要

The reaction conditions including exterior and interior factors in hydrothermal syntheses play very important roles. In this work, the influences of pH, Cit(3-)/Ln(3+) and MoO42-/Ln(3+) on the crystal structure and morphology of NaY(MoO4)(2) microstructures derived from a microwave hydrothermal synthesis were systematically studied. It was found that certain morphologies of the NaY(MoO4)(2):Tb3+ particles were only formed at critical pH values, and different amounts of Na(3)Cit and Na-2(MoO4)(2) in the reaction solution functioned in opposite ways in the crystal nucleation and growth. We also proposed that the competitive equilibrium between Na(3)Cit and Na-2(MoO4)(2) was responsible for the self-assembly behavior of the NaY(MoO4)(2):Tb3+ nano-/micro-crystals. Based on the possible growth mechanism of the NaY(MoO4)(2) microstructures, additional Cit(3-)/MoO42-/Ln(3+) molar ratios for preparing the target products were designed and the corresponding samples were prepared. It was proven that the self-assembly behavior of the NaY(MoO4)(2):Tb3+ crystals can be successfully modified under certain Cit(3-)/MoO42-/Ln(3+) molar ratios. We also discovered that the morphology can slightly affect the luminescence intensity of the NaY(MoO4)(2): Tb3+ phosphors. The temperature and concentration quenching behaviors of the NaY(MoO4)(2):Tb3+ phosphors were studied. The crossover process was found to be responsible for the temperature quenching of D-5(4) fluorescence, and the electric dipole-dipole interaction was proven to be the physical nature of the concentration quenching and the fluorescence decay process.