2018 年 126 巻 7 号 p. 551-556
In this study, Eu3+-doped ZrO2 nanophosphors were obtained by a sol–gel method with HNO3 as a catalyst, which led to white powders of small ZrO2 nanocrystals after low temperature calcination. However, exothermic reactions of NO3− were observed during the heat-treatment leading to ZrO2 crystallization. To avoid such reactions and to understand the initial crystallization of ZrO2 doped with Eu3+ ions, we developed an original route in which the xerogel powders were pre-washed in ethanol before immersing them in Eu3+ solution to remove NO3−. The effects of heat-treatment on the Eu3+ photoluminescence (PL), crystallization of ZrO2 xerogels, and Eu3+ localization were studied with PL spectroscopy, thermogravimetric analysis and powder X-ray diffraction. It was found that the amorphous ZrO2 xerogels crystallized in a tetragonal structure, with a small amount of monoclinic ZrO2 also being precipitated after longer calcination periods. Finally, the Eu3+ ions on the surface of the ZrO2 xerogels were found to diffuse into higher symmetric Zr substitutional sites in the tetragonal ZrO2 matrix after heat-treatment.