Eu-doped CaF2 is studied for use as a scintillator. Herein, the 3D spatial distribution of Eu ions doped in CaF2 crystal is evaluated. It is confirmed that both divalent and trivalent Eu ions are doped in CaF2 crystals from the luminescence spectra of the Eu-doped CaF2 crystals. Using bandpass filter, the 3D spatial distribution of divalent and trivalent Eu ions is measured, respectively. The 3D spatial distribution of divalent Eu ions with ionic radius larger than that of Ca site is nonuniform with mesh-like pattern. In contrast, the 3D spatial distribution of trivalent Eu ions with ionic radius smaller than that of Ca site is uniform. In Eu-doped CaF2 crystals grown by micropulling down method, strain caused by the difference in lattice constants between CaF2 and a seed crystal is confirmed.
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