Abstract
Conductivities of undoped and 5mol% Sr-doped NdPO4 were investigated with the dc four-probe method at temperatures from 500 to 925°C under various p(H2O) and p(O2). The conductivity of 5 mol% Sr-doped NdPO4 was higher under wet than dry atmosphere though that of undoped NdPO4 was almost independent of p(H2O). The conductivity of 5 mol% Sr-doped NdPO4 was lower under D2O than H2O containing atmosphere. These results indicated that NdPO4 conducted protons under wet atmosphere by substituting Sr for Nd. Conductivity behavior of this material versus p(H2O) or p(O2) was discussed in terms of defect equilibrium. It was concluded that protons were dominant charge carriers at investigated temperatures though electron holes became to contribute slightly to the total conductivity with increasing temperature.
