A novel and efficient method of providing moisture resistance of inorganic particles such as divalent europium activated strontium aluminate phosphors (Sr4Al14O25:Eu2+/Dy3+) was developed by. ring the phosphor in the presence of appropriate amount of ammonium fluoride at a temperature of 600-700 degrees C. Scanning electron microscopy, X-ray diffraction, FT-IR, EDAX and Photoluminescence measurements were carried out to characterize the uncoated and coated samples. The pH measurements were carried out for the water resistivity measurements. The phosphor particles became coated with a moisture-impervious thin coating that did not suppress the luminescence of the phosphor and can withstand complete immersion in water for long periods of time, showing very high water resistivity. (C) 2009 Elsevier B. V. All rights reserved.