Synthesis of Upconversion Luminophores Based on Calcium Fluoride

Abstract

The aim of our study was to synthesize a luminophore based on calcium fl uoride doped with rare-earth elements: 5 % Yb and 1 % Er, using the molten salt synthesis method.
NaNO₃ was used as a solvent and sodium fluoride NaF served as the fluorinating agent. The obtained samples were analysed and described using X-ray powder diffraction analysis, energy dispersive X-ray spectroscopy, scanning electron microscopy, and luminescence spectroscopy.
During the study we also investigated the effect of the synthesis conditions on the phase composition and the particles morphology. It was determined that single-phase samples (solid solutions based on calcium fl uoride) can only be obtained at a temperature of at least 400 °C, with the optimal exposure time being 3 hours. The composition of the obtained samples was determined. It differs from the nominal composition and can be described as Ca_0.88(Yb, Er)_0.06Na_0.06F₂. It was demonstrated that the parallel insertion of sodium and rare-earth element ions increases the solubility limit of sodium fl uoride in calcium
fl uoride. The luminescence effi ciency was 1.21 %.
As a result of this study we obtained a new material with upconversion properties.

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