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

ROCHA, LEANDRO SILVA ROSA; SCHIPANI, FEDERICO; ALDAO, CELSO MANUEL; CABRAL, LUÍS A.; SIMOES, ALEXANDRE Z.; MACCHI, CARLOS EUGENIO; MARQUES, GILMAR EUGENIO; PONCE, MIGUEL ADOLFO; LONGO, ELSON

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Lugar: Washington; Año: 2019

1932-7447

Lanthanum-doped CeO2 is a promising semiconductor for gas sensing. Acombined study applying impedance spectroscopy and first-principle calculations was performedfor pure and lanthanum-doped samples. The results showed a strong influence of the localizedCe 4f states on the electrical conduction processes, and an electrical resistance increase, as afunction of the exposure to vacuum and air atmospheres. After its modification with a rare-earthelement along with exposure to reducing and oxidizing atmospheres, the observed behaviorsuggested the presence of multi-traps, which depended on the described equilibrium between theoxygen vacancies in a disordered deep-bulk trap location. According tothe DFT results, the multi-traps were formed with the creation of an oxygen vacancy far from thedoping atom. They were considered to be responsible for the phenomena modifying the Debyelikeresponse. The transfer of electrons from Ce(III) to the adsorbed oxygen species, decreasingthe number of electrons in the 4f state, reduced the electrical conductivity by the hoppingfrequency dependence of the total resistance and capacitances. This was probably owing to theinteractions between defective oxygen and metallic species.