Identification of F+ centers in hafnia and zirconia nanopowders

•Undoped hafnia and zirconia nanopowders were prepared by solution combustion synthesis.•Radiative decay of electronic excitations were investigated using luminescence methods.•F+ centers emission bands were identified at 2.8 eV in hafnia and zirconia.•Energy transfer to the defect centers occurs via electron–hole mechanism.•Multiplication processes of electronic excitations were analyzed for zirconia.

Luminescence properties of undoped hafnia and zirconia nanopowders prepared by solution combustion synthesis were investigated under photo- and electron-beam excitation in 10–400 K temperature range. Along with the main luminescence band revealed in investigated materials at low temperatures at 4.2–4.3 eV and ascribed to the emission of self-trapped excitons, there are luminescence bands due to defects and impurities introduced during sample preparation. At room temperature the latter emissions dominate in the luminescence spectra as the intrinsic self-trapped exciton emission is quenched. Analysis of decay kinetics of defect centers allowed identification of F+ centers emission at 2.8 eV with lifetimes ∼3–6 ns in hafnia and zirconia under intra-center excitation.