Glasses with compositions $(100-x)\mathrm{Si}{\mathrm{O}}_2-x\mathrm{Hf}{\mathrm{O}}_2:0.3{\mathrm{Eu}}^{3+}$ (molar ratio, $x=0,10,20,30$ ) for optical applications were prepared using the sol-gel route. The introduction of hafnium into the glass matrix induced the energy splitting of the ${}^{7}F_2$ state of ${\mathrm{Eu}}^{3+}$ ions. Furthermore, fluorescence line narrowing (FLN) spectra indicated that ${\mathrm{Eu}}^{3+}$ clustering occurred in glasses containing no hafnium. The addition of hafnium promoted better dispersion of ${\mathrm{Eu}}^{3+}$ ions in the glass matrix. The role of hafnium on modifying the properties of glasses was discussed with respect to x-ray diffraction and FLN analysis.