Grain boundary and grain interior conduction in γ′-Bi2MoO6

Impedance spectroscopy of fine grained (<10 μm) γ′-Bi2MoO6 samples, in the frequency range of 0.1 Hz-250 kHz, relevant to sensor applications, up to 800 °C, has been used to characterize grain boundary and grain interior contributions to conduction. Above 500 °C, the grain boundary contribution is no longer rate limiting and conduction is dominated by the grain interior component. The corresponding activation energies are 0.98 eV for grain boundary and 0.73 eV for grain interior components. The weak dependence of conductivity on oxygen partial pressure below 500 °C can be attributed to electrode-electrolyte interface phenomena, whereas the robust response to ethanol is commensurate with changes in intrinsic ionic conductivity.