Electronic conductivity of Ce_0.8Gd_0.2−xPr_xO_2−δ and influence of added CoO

Abstract

251 83 367 05 Doped ceria and ceria based solid oxide solutions show a unique combination of oxygen ion mobility, electronic conductivity, and high catalytic activity for redox reactions. In this work, the minority conductivity of electrons has been measured directly as a function of the composition of ceria-praseodymia based solid solutions in order to maximize the electronic conductivity without depressing the oxygen ion mobility. The influence of Co as well as the Gd/Pr dopant ratio on the electronic conductivity of ceria-praseodymia pellets was studied for the compositions Ce 0.8 Gd 0.2Àx Pr x O 2Àd (0.05 x 0.15) with and without an additional Co content of 0.02 with respect to the formula. The Hebb-Wagner polarization technique was used with ion-blocking microcontacts. In the temperature range 700-800 8C, the presence of high amounts of praseodymium increases the p-type conductivity by a factor of more than 10 for oxygen partial pressures higher than 10 À10 bar. Co-doped ceria-gadolinia-praseodymia solid solutions showed a further increase of the electronic conductivities in a partial pressure range where the Co-free materials showed the minimum of the electronic conductivities. It is assumed that the effect of the additional cobalt doping is due to electronic short circuits along the grain boundaries via segregated CoO.

Assessment of the Effect of Transition Metal Oxide Addition on the Conductivity of Commercial Gd-Doped Ceria

“…23,24 Pr as a redox active material also provides an additional oxygen partial pressure dependent maximum of the electronic conductivity due to the reduction from Pr 4+ to Pr 3+ and a related polaron hopping mechanism within a certain oxygen partial pressure range. 23,25,26 A comparable effect has also been confirmed for Mn doping in YSZ or ceria after sintering at certain temperatures to preserve the Mn 3+ state within the material [27][28][29] and is also conceivable for other redox-active transition metal cations.…”

“…An extended description of the microcontact measurement method can be found in previous publications. 24,[63][64][65] Measurements were executed at temperatures between 800-400…”

“…The effect of small amounts of various transition metal oxides on the electronic partial conductivity has already been investigated previously in detail by us for Cr, 31 Co, 25 Mn 24 and Zn addition. 40 A detailed comparative study of the effect of transition metal addition on the electronic conductivity over a large temperature and oxygen partial pressure range deploying a commercially available model material has not been performed to date, though.…”

The model case of an oxygen storage catalyst – non-stoichiometry, point defects and electrical conductivity of single crystalline CeO2–ZrO2–Y2O3solid solutions

“…s ion c s e . 50,51 Hence, the boundary condition at the Pt micro contact corresponds to a vanishing partial oxygen ion current i O 2À at r = a, if considered as a hemispherical contact surface with radius a,…”

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

“…CoO x , has been reported as a ceria sintering aid and promoter of the electronic conductivity through the grain boundaries [12][13][14][15] . Here, the addition of CoOx is intended to promote the formation of an electronic network that bridges the transport of electrons with the LSM particles.…”