Molten salt synthesis, characterization, and luminescence of SrWO₄, SrWO₄:Tb³⁺ and SrWO₄:Eu³⁺ powders

Abstract

SrWO₄, SrWO₄:Tb³⁺, and SrWO₄:Eu³⁺ powders were synthesized by a method of molten salt. XRD patterns showed that the synthesized powders have a pure tetragonal scheelite structure without the presence of deleterious phases. Scanning electron microscopy images show that powders are in the range of 20–35 nm. The emission spectrum of SrWO₄ shows the emission peak in the blue spectral region. The excitation spectra of SrWO₄:Tb³⁺ and SrWO₄:Eu³⁺ show the energy transfer from WO₄ ²⁻ group to Tb³⁺ and Eu³⁺ ions with a high efficiency. The emission spectrum of SrWO₄:Tb³⁺ shows the green emission at 545 nm corresponding to the ⁵D₄ → ⁷F₅ transition of Tb³⁺. The emission spectrum of SrWO₄:Eu³⁺ shows the red emission located at 612 nm corresponding to the ⁵D₀ → ⁷F₂ transition of Eu³⁺. The asymmetry ratio of SrWO₄:Eu³⁺ is found to be 5.54, which indicates that the Eu³⁺ ions are located in a lower symmetric site.