<p>A new method of synthesis for NaYF₄ is reported. The method involves highly exothermic solid-state metathesis reaction between metal chlorides and NaF. The synthesis is very fast and the metathesis reaction is over within several minutes. Initiation of the reaction is marked by the appearance of the flame and the completion by its extinguishing. The product was characterised by various techniques like X-ray diffraction, electron microscopy, energy dispersive spectroscopy and elemental mapping. Mixed α and β phases were formed with cubic and hexagonal structures, respectively. Ce³⁺- and Gd³⁺-activated NaYF₄ phosphors were successfully synthesised by this method as could be judged from the typical emission and excitation spectra. Solid-state metathesis thus provides a tool for fast, simple synthesis of this important class of phosphors.</p>