Luminescence study of oxygen vacancies in lanthanum hafnium oxide, La2Hf2O7

► The oxygen-vacancy-related luminescence of La2Hf2O7 consists of a band with a peak around 460 nm. ► The optical and X-ray excited emission spectra differ. ► The experimental results are in general agreement with predicted spectroscopic properties. ► The luminescence of La2Hf2O7 varies with the atmosphere and temperature of the synthesis process.