In this study, Eu 3+-doped ZrO 2 nanophosphors were obtained by a solgel method with HNO 3 as a catalyst, which led to white powders of small ZrO 2 nanocrystals after low temperature calcination. However, exothermic reactions of NO 3 ¹ were observed during the heat-treatment leading to ZrO 2 crystallization. To avoid such reactions and to understand the initial crystallization of ZrO 2 doped with Eu 3+ ions, we developed an original route in which the xerogel powders were pre-washed in ethanol before immersing them in Eu 3+ solution to remove NO 3 ¹. The effects of heat-treatment on the Eu 3+ photoluminescence (PL), crystallization of ZrO 2 xerogels, and Eu 3+ localization were studied with PL spectroscopy, thermogravimetric analysis and powder X-ray diffraction. It was found that the amorphous ZrO 2 xerogels crystallized in a tetragonal structure, with a small amount of monoclinic ZrO 2 also being precipitated after longer calcination periods. Finally, the Eu 3+ ions on the surface of the ZrO 2 xerogels were found to diffuse into higher symmetric Zr substitutional sites in the tetragonal ZrO 2 matrix after heat-treatment.