orbitals of oxygen ions gives to an
anionic valence band. The Ce–O bonds have a stronger ionic
character, and hence a smaller contribution of the Ce 5d and 4f
orbitals in the VB, in CeO2 [25]. The band gap between the
anionic band and the cationic band is 3.01 eV. By doping CeO2
with Pr4+ ions, the 4f1 electron of the praseodymium valence