Crystal structures of hafnia are discussed and it is shown that addition of about 7 at.% of Lu to the HfO 2 host lattice enforces the mixed composition to crystallize in cubic structure even at room temperature. Without Lu HfO 2 crystallizes in monoclinic structure. Luminescence and luminescence excitation spectra of Hf 0.93Lu 0.07O 1.965 are presented and discussed for powders prepared at different temperatures (600-1000 °C) and with different content of Eu. It is shown that decay of the 595.4 nm luminescence is longer (2.5 ms) than the 610 nm (1.6 ms). Radioluminescence efficiency of the cubic Hf 0.93Lu 0.07O 1.965 is low and does not exceed 10% of the commercial Gd 2O 2S:Eu.