Abstract
Electrical conduction in undoped and Ca-doped NdBO3 with the orthorhombic aragonite-type structure was investigated by using conductivity measurements under 0.4-5kPa of p(H2O) and 0.01-100kPa of p(O2) at 500-925°C. From humidity dependence and H/D isotope effect of the conductivity, it was found that NdBO3 became a protonic conductor under wet conditions by partially substituting Ca for Nd. The conductivities of 1mol%Ca-doped NdBO3 were 10-5.4-10-4.1 S⋅cm-1 under wet condition at 500-925°C. As temperature increased, electron holes became to contribute to the conduction, although protons were estimated as dominant charge carriers under the conditions employed. The p(H2O) and p(O2) dependence of the conductivity were discussed in terms of defect equilibrium. Conductivity behaviors as well as conductivity values of Ca-doped NdBO3 were rather similar to those of the Sr-doped LaBO3 with the same crystal structure.
