Experimental and Ab Initio Studies of Deep-Bulk Traps in Doped Rare-Earth Oxide Thick Films

Lanthanum-doped CeO2 is a promising semiconductor for gas sensing. A combined study applying impedance spectroscopy and first-principle calculations was performed for pure and lanthanum-doped samples. The results showed a strong influence of the localized Ce 4f states on the electrical conduction processes, and an electrical resistance increase, as a function of the exposure to vacuum and air atmospheres. After its modification with a rare-earth element along with exposure to reducing and oxidizing atmospheres, the observed behavior suggested the presence of multi-traps, which depended on the described equilibrium between the oxygen vacancies (Vox ↔ VO. ↔VO..) in a disordered deep-bulk trap location. According to the DFT results, the multi-traps were formed with the creation of an oxygen vacancy far from the doping atom. They were considered to be responsible for the phenomena modifying the Debye-like response. The transfer of electrons from Ce(III) to the adsorbed oxygen species, decreasing the number of...