Multitype of cerium centers in optical nanoceramics on the bases of ВаF$_2$–СеF$_3$

The absorption (SP) and photoluminescence (PL) spectra of ВаF$_2$–СеF$_3$ crystals and nanoceramics based on them have been investigated. In samples of both types, under excitation at the excitation band $\lambda_{\mathrm{ex}}$ = 285 nm, a doublet photoluminescence band with maxima at 305 and 320 nm (Ce1 centers) was found. In contrast to this, in optical nanoceramics were found 3 additional PL bands: $\lambda_{\mathrm{ex}}$ = 310 nm, $\lambda_{\mathrm{rad}}$ = 370 nm (Ce2 centers), $\lambda_{\mathrm{ex}}$ = 250 nm, $\lambda_{\mathrm{rad}}$ = 425 nm (Ce3 centers) and $\lambda_{\mathrm{ex}}$ = 345 nm, $\lambda_{\mathrm{rad}}$ = 550 nm (Ce4 centers). The nature of the found centers has been identified.