Ce3+ ion-induced distortion in a perovskite-structured KMgF3 single crystal

We investigate the local structural distortion induced by

ion in a (cubic) perovskite-structured KMgF₃ crystal for potential vacuum ultraviolet (VUV) applications. The crystal with 1.0 mol% nominal doping concentration exhibits five absorption bands centered at 196, 203, 209, 227, and 233 nm and two emission bands centered at 266 and 282 nm. These absorption and emission bands are attributed to the 4f$-$5d transitions of the

ion. Our Ce K- and

-edge XAS analyses confirm the presence of

oxidation state in the KMgF₃ crystal. Our analyses reveal a significantly distorted coordination environment which has a coordination number (CN) of $5.03\pm 0.55$ and an average Ce–F bond length of $2.44\pm 0.01$ Å. Strong mixing of the 4f and 5d states and large ligand-field effects are also implied in the Ce

-edge XANES spectrum, as evidenced by an intense pre-edge peak. Optically, these mixing and ligand field effects conform to the large crystal field splitting of 1.03 eV (8285

). Although this was the case,

-doped KMgF₃ remains a candidate VUV optical material due to its small Stokes shift of 0.64eV (5141

).