Sonochemical synthesis of optically active fluorides

Abstract

Up-conversion is the optical property of materials which have ability to convert low energy photons (usually from infrared spectrum) into higher energy photons (from visible spectrum). Such compounds, usually lanthanide doped oxides or fluorides, have many applications in photoluminescence science and technology today. Currently, (β) NaYF4:Yb,Er polymorph is considered to be the most efficient up-converting material. Its synthesis usually includes the usage of toxic solvents, long-term heating, high pressures, controlled gas atmosphere, etc. The aim of this work was to utilize rarely applied sonochemical synthesis for the stabilization of (β) NaYF4:Yb,Er phase under mild and environmental friendly conditions. For this purpose, we performed ultrasonic treatment of common nitrate precursors and sodium fluorine for a different time. The obtained powders were analyzed in order to determine their phase composition and thermal stability, morphology, dopants distribution, particles surface purity and luminescent characteristics. Owing to this, the chemical and crystal phase transformations that occurred in specified periods of synthesis time are explained in detail. Moreover, it was shown that obtaining of uniformly doped (β) NaYF4:Yb,Er mosocrystalline particles is possible after 2h of sonication.