Defect-property correlations in garnet crystals: The electrical conductivity and defect structure of luminescent cerium-doped yttrium aluminum garnet

The conduction mechanisms in cerium-doped yttrium aluminum garnet (Ce:YAG) have been studied as a function of temperature and PO2. ac conductivity and ionic transference measurements show that Ce:YAG is a mixed ionic-electronic conductor with an ionic conductivity characterized by an activation energy of 2.3 eV. A derived thermal band-gap energy of 6.1 eV compares favorably with the optically measured band gap. Conductivity and transference measurements support a defect model with a fixed number of doubly-ionized oxygen vacancies as the primary defect; the energy to produce such vacancies is calculated to be 7.8 eV.