Praseodymium doped ceria: Model mixed ionic electronic conductor with coupled electrical, optical, mechanical and chemical properties

Chemomechanics of ionically conductive ceramics for electrical energy conversion and storage

“…In the non-stoichiometric materials that comprise the cathode and anode (and potentially the electrolyte), spatial variations in oxygen vacancy concentration parallel corresponding variations in oxygen partial pressure. This gradient in vacancy concentration correlates with Vegard expansion in many non-stoichiometric oxides, an effect which is magnified at the high operating temperatures of SOFCs [3,4].…”

“…For SOFCs, electrode and electrolyte materials are commonly perovskite-or fluorite-structured oxides that can tolerate large oxygen vacancy concentrations and many different atomic impurities (dopants) at high concentration. For the cathode, mixed ionic-electronic conductors such as La 1−x Sr x CoO 3−δ (LSC), SrTi 1−x Fe x O 3−δ (STF), or Pr x Ce 1−x O 2−δ (PCO) are selected, as such compounds may enhance oxygen reduction reactivity by extending active sites from simply triple phase boundaries (as for solely electronic conductors) to the full area of the electrode [4][5][6]. The electrolyte, on the other hand, must be both electronically insulating and highly conductive to oxide ions, and so materials such as yttria stabilized zirconia (YSZ) or Gd x Ce 1−x O 2−δ (GDC) are typically used as solid electrolytes.…”

“…1(e), which shows lithium intercalating into a cathode particle at a lithium vacancy site while an electron reduces a nearby cobalt ion. There are three classes of lithium storage compounds used in cathodes of commercial lithium-ion batteries.These include layered lithium-containing materials, such as LiCoO 2 that adopt the α-NaFeO 2 ordered rocksalt structure; spinel oxides such as LiMnO 4 ; and olivines such as LiFePO 4 . To minimize the impedance and maximize the useful lifetime of the LIB, these materials must be fracture resistant.…”

Optimization of SOFC Composite Cathodes Based on LSM and Doped Cerias Ce0.8Ln0.2O2-δ(Ln = Gd, Er, Tb and Pr)

“…The addition of the ceria phase enhances the ionic transport, increasing the triple phase boundary (TPB) length in the electrode where gaseous oxygen comes into contact with the ion and electron conducting phases, and the electrochemical reactions take place 7 . Furthermore, by introducing lanthanide elements with mixed valence (as Pr and Tb) in the ceria lattice, mixed ionic-electronic conductivity (MIEC) may be promoted even at high oxygen partial pressures (pO 2 > 10 -5 atm) [8][9][10][11] . Thus, the TPB area is further increased since the whole surface area of the ceria in contact with the gas is active for the electrochemical reaction in addition to the LSM-electrolyte interface.…”

“…Electronic levels are introduced in the bandgap when Pr is incorporated in the structure 10 , the electronic conductivity is enhanced via small polaron hopping between Pr 3+ and Pr 4+ . Around 700 ⁰C the concentration of both oxidation states is equal producing a maximum in the small polaron hopping.…”