High yield syntheses of reactive fluoride K1 − x(Y,Ln)xF1 + 2x nanoparticles

This article reports the first synthesis of fluorine nanoparticles composing K1 − x(Y,Ln)xF1 + 2x (with 0.56 < x < 0.73 and Ln = Er3+ or Eu3+) via a room temperature, coprecipitation method in aqueous solution. Nanoparticles with a fluorite-type structure are prepared using synthesis conditions that are highly flexible in terms of stoichiometry, acidity, concentration, fluorine source and reaction time. Those highly reactive nanoparticles can be considered as good precursor to achieve transparent ceramics for laser applications: the cubic symmetry is preserved upon heating despite large concentration of doping rare earth (0–15%). This method is much greener that traditional preparations for such fluorine materials, being carried out in water and avoiding the use of toxic, corrosive and more expensive fluorine sources such as HF or CF4 and SF6 gas. Nonetheless, the amount of oxygen in these materials is low, with absorbed water molecules and trapped hydroxyl groups effectively being removed above 450 °C. Finally, we report the luminescence properties of the erbium doped materials, showing that materials presenting long decay times can be achieved via this route.