Electrical Conduction Properties of Sr-Doped LaPO[sub 4] and CePO[sub 4] under Oxidizing and Reducing Conditions

Electrical conduction properties of Sr-doped and Sr-doped under and conditions were investigated with conductivity measurements. Conductivities of Sr-doped were at under wet reducing conditions and were close to those under wet oxidizing conditions. It was found from the H/D isotope effect on conductivity that the material showed dominant protonic conduction under wet reducing conditions. As for Sr-doped , conductivities were at under wet oxidizing conditions and much higher than those of Sr-doped under the same conditions. Such high conductivities of Sr-doped seemed attributable to electronic conduction due to partial oxidation of to caused by substituting for . Under wet reducing conditions, however, conductivities of the material decreased to at , which was almost comparable with those of Sr-doped . It was concluded that Sr-doped showed mixed protonic and p-type electronic conductions under wet reducing conditions. Based on the results of conductivity measurements, defect structures in Sr-doped and under wet oxidizing and reducing conditions are discussed.