Hopping conduction in a mixed valence oxide system: Pr _{1 y}Gd _{y}O _{1.5+δ}
Abstract
The electrical conductivity of σphase Pr _{1 y}Gd _{y}O _{1.5+ δ} ( y = 0.0, 0.1, 0.2, and 0.4) was measured as a function of temperature and oxygen partial pressure. The dependence of the electrical conductivity of Pr _{1 y}Gd _{y}O _{1.5+δ} on the composition was determined by combining gravimetric and conductivity data. The results are consistent with the smallpolaron model of localized charge carriers hopping between two adjacent Pr ions in different valence states. The following equation was quantitatively examined: σ = ns(1 s) pek_{h}, where n is the concentration of total Pr ions, s is the fraction of Pr ^{4+} ions in total Pr ions, p is the probability that cationic positions are occupied by mixed valence ions, and k_{h} is a constant characteristic of the chargetransfer process between different valence states. It was found that k_{h} increases slightly with increasing δ. This dependence is discussed in terms of the observed activation energy and the degree of delocalization of the 4 f electrons.
 Publication:

Journal of Solid State Chemistry France
 Pub Date:
 September 1976
 DOI:
 10.1016/00224596(76)901444
 Bibcode:
 1976JSSCh..19...13E