Changes in the electrical properties of CeO2 through alterations in defects caused by Mn doping

Mn-doped CeO2 nanoparticles were synthesized using a microwave-assisted hydrothermal method and analyzed through photoluminescence spectroscopy, positron annihilation lifetime spectroscopy (PALS), and electrical resistance measurements, with the aim of determining the effect of Mn incorporation on the electrical properties of ceria. The present study reveals that the initial introduction of Mn results in the proliferation of small defective structures, attributed to the substitution of Ce4+ by Mn2+ and Mn3+. This transformation leads to the increased formation of Ce3+ species, which are linked to the presence of faulty structures associated with oxygen vacancies. The photoluminescence analysis showcases a notable rise in the number of neutral, singly, and doubly ionized oxygen vacancies following the addition of Mn. Concurrently, in pure sample, electrical measurements indicate that Ce3+ species govern the local charge transfer mechanism, facilitated by the formation of Ce 4f1 orbitals. However, the electrons trapped in various oxygen vacancy-related defect states are responsible for the elevation in activation energy observed in Mn-doped CeO2 samples. Furthermore, electrical measurements exhibit consistent activation energies across all samples when exposed to varying atmospheric conditions. Additionally, the enhanced response in Mn-doped samples is primarily attributed to a significant increase in carrier density.