TY - JOUR
T1 - The electrical and defect properties of Bi3Zn2Sb3O14 pyrochlore
T2 - A grain-boundary phase in ZnO-based varistors
AU - Clayton, Jane
AU - Takamura, Hitoshi
AU - Metz, Renaud
AU - Tuller, Harry L.
AU - Wuensch, Bernhardt J.
N1 - Funding Information:
The first equilibrium transport studies of Bi3Zn2Sb3O14 pyrochlore have shown the material to be a mixed ionic-electronic conductor. This is supported by the Po2 dependence of the conductivity and the ionic transference number measurements. P-type conductivity dominates at high Po2, under oxidizing conditions, and n-type conductivity dominates at low Po2, under reducing conditions. Additionally, a considerable ionic contribution to the conductivity is apparent due to the presence of the shallow minimum in conductivity measurements. The presence of this contribution was confirmed with the results of the concentration cell measurements. Employing a model in which Frenkel defects are assumed to be dominant, permitted the extraction of a number of key thermodynamic and kinetic data from the electrical conductivity data. Such results include the enthalpies of reduction, oxidation, the sum of oxygen vacancy formation and migration and the band gap energy.
Funding Information:
This work was supported by the Department of Energy, Basic Energy Sciences under contract #DE-FG02-86ER45261. The results contributed to the present paper by one of us (Jane Clayton) were obtained during a Summer Internship supported by a National Science Foundation Research Experiences for Undergraduates (REU) program. This grant is provided as a supplement to a Materials Research Science and Engineering Center (MRSEC) award to MIT’s Center for Materials Science and Engineering, DMR 9808941. Gratitude is also expressed to the MIT Materials Processing Center for funding to meet her travel expenses. We are indebted to Alain Marchand, Henri Delalu and Jean Jacques Counioux for assistance in the synthesis of the pyrochlore powder.
PY - 2001/11
Y1 - 2001/11
N2 - The electrical conductivity of Bi3Zn2Sb3O14 pyrochlore was studied as a function of temperature and partial pressure of oxygen. Conductivity measurements by ac complex impedance analysis and ionic transference number measurements show this pyrochlore to be a mixed ionic-electronic conductor with an energy band gap of 3.15 ± 0.9 eV. A defect model in which Frenkel defects on the oxygen lattice are dominant is confirmed. Enthalpies of reduction, oxidation and the sum of oxygen vacancy formation and migration were found to be 4.82 ± 0.8 eV, 1.48 ± 1.0 eV and 1.67 ± 1.0 eV respectively.
AB - The electrical conductivity of Bi3Zn2Sb3O14 pyrochlore was studied as a function of temperature and partial pressure of oxygen. Conductivity measurements by ac complex impedance analysis and ionic transference number measurements show this pyrochlore to be a mixed ionic-electronic conductor with an energy band gap of 3.15 ± 0.9 eV. A defect model in which Frenkel defects on the oxygen lattice are dominant is confirmed. Enthalpies of reduction, oxidation and the sum of oxygen vacancy formation and migration were found to be 4.82 ± 0.8 eV, 1.48 ± 1.0 eV and 1.67 ± 1.0 eV respectively.
KW - Electrical conductivity
KW - Grain boundary barriers
KW - Ionic transference number
KW - Mixed conductor
KW - Varistor
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U2 - 10.1023/B:JECR.0000027951.41051.11
DO - 10.1023/B:JECR.0000027951.41051.11
M3 - Article
AN - SCOPUS:0035520216
VL - 7
SP - 113
EP - 120
JO - Journal of Electroceramics
JF - Journal of Electroceramics
SN - 1385-3449
IS - 2
ER -