Molten Salt Synthesis of Color Tunable NaCa2Mg2(VO4)3:Eu3+ Phosphors and Their Luminescent Properties.

A series of color tunable NaCa2-xMg2 (VO4)3 : xEu3+ (0≤x≤0. 10) phosphors were synthesized by molten salt method using cheap NaCl as molten salt. The effects of synthesis conditions and Eu3+ doping on the structure and luminescence properties of the samples were investigated in details. The results show that the optimum reaction conditions for the synthesis of NaCa2Mg2 (VO4)3 are reaction temperature of 800 °C, reaction time of 0. 5 h and mass ratio of raw material to molten salt of 1:3. The obtained samples are NaCa2Mg2 (VO4)3 pure phase with higher crystallinity. The micromorphology of the samples changed from coral-like to smooth irregular polyhedron with the increase of temperature. Eu3+ doping has little effect on the crystal structure of NaCa2 Mg2 ( VO4)3, but great effect on its luminescence properties. With the increase of Eu3+ concentration (x), the characteristic emission band intensity of VO43- gradually decreases, while the characteristic emission peak intensity of Eu3+ first increases and then decreases, reaching the maximum when x = 0. 06. Therefore, the luminous color of the samples can be modulated by changing the Eu3+ concentration, from green to yellow-green, yellow, yellow-white and orange-red. According to the fluorescence spectrum and fluorescence lifetime analysis, it is confirmed that the energy transfer process of VO43-to Eu3+ exists in NaCa2 Mg2 (VO4)3 : Eu3+ phosphors, and the energy transfer efficiency is about 23%. The thermal stability analysis shows that when the temperature increases from room temperature (298. 15 K) to 398. 15 K, the retaining ratio of the main emission peak intensity of NaCa2 Mg1. 94 (VO4)3:0. 06Eu3+ phosphor at 614 nm is 68. 4%, showing its good thermal stability. [ABSTRACT FROM AUTHOR]