Synthesis and luminescent properties of NaLa(MoO4)2:Eu3+,Tb3+ phosphors by microwave-assisted sol–gel method

Abstract

A series of NaLa(MoO4)2:xEu3+, 5 %-xTb3+ phosphors were synthesized by microwave-assisted sol–gel method using citric acid as complexing agent, followed by a heat treatment at 700–900 °C. The XRD results indicate that the samples have the tetragonal scheelite-type structure with high purity and crystallinity. The scanning electron microscope images demonstrate that the particles of the phosphors are irregular blocky with the size of 1–6 μm. Photoluminescence spectra show that the emission intensity of the phosphors calcined at 900 °C is the strongest. When the Eu3+ and Tb3+ ions are co-doped into the NaLa(MoO4)2 host lattice, the emission spectra show the characteristic transitions of Eu3+ and Tb3+. The luminescence colors of the phosphors can be turned from red, through yellow and green-yellow, to green by changing the relative doping concentrations of Eu3+ and Tb3+. A series of Eu3+ and Tb3+ co-doped NaLa(MoO4)2 phosphors have been successfully synthesized by microwave-assisted sol–gel method. This method exhibits many advantages of short gelling and drying time, energy saving, uniform composition, and so on. The photoluminescence color of phosphors can be tuned from green, through green-yellow and yellow, to red by controlling the doping concentration of Eu3+ and Tb3+.