Electrical conductivity of (Er,U)O2+x and (Ce,U)O2+x

Electrical conductivity and non-stoichiometry in the (U,Gd)O2±x system

“…In addition, the corresponding new oxygen non-stoichiometry z at the inflection is also independent of the Gd contents and has a value of about 0.1. The observed oxygen partial pressure at an inflection point and a corresponding oxygen non-stoichiometry z are found to be almost the same as those observed in the UO 2 base fluorites such as UO 2+x , (U 1Ày Y y )O 2+x [29] and (U 1Ày Er y )O 2+x [40], when the experimental data of these systems are reanalyzed using our new stoichiometry, i.e., UO 2+z , (U 1Ày Y y )O 2Ày/2+z and (U 1Ày Er y ) O 2Ày/2+z . This implies that the electrical conductivity curves of (U,Ln 3+ )O 2Ày/2+z are inflected when the oxygen non-stoichiometry z exceeds 0.1 regardless of the amount or species of the doped cation.…”

“…On the other hand, the slopes of the non-stoichiometry curves of (U 0.913 Gd 0.087 )O 2±x and (U 0.831 Gd 0.169 )O 2±x in a high p O 2 region show the value of 1. Similar differences between a and b are generally found in (U,Ln 3+ )O 2±x systems [40]. But, any reasonable correlations between the two exponents have not been suggested as yet.…”

“…The charge neutrality condition of ½h Å ¼ ½Ln 0 U ¼ constant is frequently introduced to interpret the flat electrical conductivity dependence in the intermediate oxygen partial pressure region of the (U,Ln 3+ )O 2±x system [34,40]. The electrical conductivity is constant when the ½h Å ¼ ½Ln 0 U ¼ constant condition …”

“…The concentration of mobile charge carriers is proportional to the oxygen deviation from the stoichiometry, which is determined by the oxygen partial pressure. It is known that the hole mobility for the same type of oxygen defects is almost independent of the change in the oxygen partial pressure [29,40]. This implies that the a and b values in the x / p 1=a O 2 and r / p 1=b O 2 equations should be closely interrelated.…”

“…Several researchers have measured the non-stoichiometry and electrical conductivity in the (U,Ln 3+ )O 2±x system at various oxygen partial pressures and temperatures, and they have suggested various defect models based on those measurements [29][30][31][32][33][34][35][36][37][38][39][40]. The suggested defect models cover wide ranges of the substituted species, substitution amounts, and measuring temperatures so much so the oxygen defect models in a Ln 3+ substituted UO 2 are difficult to integrate in a consistent manner.…”