Abstract
A thermally stimulated luminescence (TSL) study in the temperature range 20–300 °C has been performed after x-ray irradiation on mixed crystals and on Several glow peaks have been detected, namely at 50 °C, 100–130 °C (composite structure), 175 °C and 225 °C, whose intensities are dependent upon the crystal composition. The spectrum of the emitted light features one band at 3.45 eV due to the transition of the ion, in good agreement with the UV excited emission spectrum. A detailed analysis of the trap depths of the peaks has been performed in the case of by partial cleaning of the glow curve. A constant energy value of approximately 1.15 eV has been found for all TSL peaks. From this result, and from the lack of a thermally stimulated current signal in the whole temperature range, it is possible to propose that TSL recombination is governed by a thermally assisted tunneling process from one trap level found at different distances from cerium emitting centers. A strong increase of TSL intensity has been observed after a prolonged annealing treatment in a vacuum atmosphere, suggesting that the electron traps are probably related to oxygen vacancies. Under this hypothesis, the relation between the frequency factors of the TSL peaks and the shortest O-Ce distances in the lattice has been investigated: an exponential dependence has been found, in accordance with what is expected for the thermally assisted tunneling recombination process.
- Received 29 September 1999
DOI:https://doi.org/10.1103/PhysRevB.61.8081
©2000 American Physical Society