Optical emission due to ionic displacements in alkaline earth titanates

Abstract Optical emission spectra in the 300–700 nm range were collected from single crystal CaTiO 3 , SrTiO 3 and BaTiO 3 , and polycrystalline CaTiO 3 samples, that were irradiated at room temperature using a Febetron 706 variable energy pulsed-electron-beam generator. The long-lived emissions (up to microseconds after the electron pulse) consist of broad (halfwidths ∼100 nm) bands centred around 380, 425, and 445 nm for CaTiO 3 , SrTiO 3 and BaTiO 3 , respectively. These emission bands are similar to cathodoluminescence emissions from 25 keV electron irradiation attributed by others to direct conduction-valence band transitions in unreduced samples and oxygen vacancies in reduced samples. CaTiO 3 , SrTiO 3 and BaTiO 3 all have emission thresholds of 0.26±0.02 MeV. This corresponds to a threshold displacement energy for oxygen, E d of 45±4 eV.