Research of optical absorption and luminescence spectra of double-perovskite calcium tungstate co-doped with Yb³⁺/Ho³⁺

Abstract

Ho³⁺/Yb³⁺ co-doped Ca₃WO₆ phosphors synthesized via a conventional solid-state reaction method and characterized structurally by X-ray diffraction analysis. For the investigation of particle size and the surface morphology of the prepared material the field emission scanning electron microscopy have been performed. No absorption band around 980 nm has been observed in the Ho³⁺ doped phosphors whereas a broad band around 980 nm in the Ho³⁺/Yb³⁺ co-doped phosphors corresponding to ²F_5/2 → ²F_7/2 absorption transition of Yb³⁺ ion has been detected. Up-conversion emission band have been observed in the visible region upon excitation with a 980 nm laser diode. The thermal stability of luminescence of Ca₃WO₆:Ho³⁺/Yb³⁺ was also investigated and the activated energy was deduced to be 0.173 eV, which shown good thermal stability. The study provides deep insights into the understanding of bidirectional energy transfer in UC mechanism, offering the possibility for applications in color displays and anti-counterfeiting techniques.