Luminescence properties of ${\mathrm{Eu}}^{3+}$ ions in $\mathrm{K}\mathrm{Mg}{\mathrm{F}}_3$ are investigated by site-selective laser-excitation spectroscopy. Two different types of ${\mathrm{Eu}}^{3+}$ centers are identified in $\mathrm{K}\mathrm{Mg}{\mathrm{F}}_3:{\mathrm{Eu}}^{3+}$ $(0.01\mathrm{mol}\%)$. Two lines at 570.16 and $573.87\mathrm{nm}$ corresponding to two ${\mathrm{Eu}}^{3+}$ centers are observed in the excitation spectrum of the ${}^{7}F_0\to {}^{5}D_0$ transition. The former line is much stronger than the latter line. The dominant ${\mathrm{Eu}}^{3+}$ center is due to the isolated ${\mathrm{Eu}}^{3+}\text{−}{V}_c$ (charge-compensating vacancies) pair and the other ${\mathrm{Eu}}^{3+}$ centers are attributable to a clustering of ${\mathrm{Eu}}^{3+}\text{−}{V}_c$ pairs. At high concentration of Eu ions (above $0.5\mathrm{mol}\%$), new excitation lines due to clustering of ${\mathrm{Eu}}^{3+}\text{−}{V}_c$ pairs appear in the excitation spectra of the ${}^{7}F_0\to {}^{5}D_0$ transition. Luminescence from most of the ${\mathrm{Eu}}^{3+}$ centers is quenched as the temperature is raised to $305\mathrm{K}$. Such a luminescence quenching is explained by an energy transfer from ${\mathrm{Eu}}^{3+}$ to an H center formed in the vicinity of ${\mathrm{Eu}}^{3+}\text{−}{V}_c$ pair.

• Received 28 May 2004

DOI:https://doi.org/10.1103/PhysRevB.70.205113