Nanostructured CaWO₄, CaWO₄ : Pb²⁺ and CaWO₄ : Tb³⁺ Particles: Polyol-Mediated Synthesis and Luminescent Properties

Abstract

Nano-submicrostructured CaWO 4 , CaWO 4 : Pb 2+ and CaWO 4 : Pb 3+ particles were prepared by polyol method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), thermogravimetry-differential thermal analysis (TG-DTA), photoluminescence (PL), cathodoluminescence (CL) spectra and PL lifetimes. The results of XRD indicate that the as-prepared samples are well crystallized with the scheelite structure of CaWO 4 . The FE-SEM images illustrate that CaWO 4 and CaWO 4 : Pb 2+ and CaWO 4 : Tb 3+ powders are composed of spherical particles with sizes around 260, 290, and 190 nm respectively, which are the aggregates of smaller nanoparticles around 10–20 nm. Under the UV light or electron beam excitation, the CaWO 4 powders exhibits a blue emission band with a maximum at about 440 nm. When the CaWO 4 particles are doped with Pb 2+ , the intensity of luminescence is enhanced to some extent and the luminescence band maximum is red shifted to 460 nm. Tb 3+ -doped CaWO 4 particles show the characteristic emission of Tb 3+ 5 D 4 – 7 F J ( J = 6 – 3) transitions due to an energy transfer from WO 4 2− groups to Pb 3+ .