Current-voltage dependence for In2O3-SrO
ceramics contains three regions: linear at low voltages,
superlinear at intermediate voltages (current is increased
stronger than voltage) and sublinear at higher voltages (current
is increased weaker than voltage). The appearance of sublinear
region after superlinear one cannot be explained by the existing
theory. Based on the experimental data (electrical measurements,
SEM and XPS) a modified grain-boundary model is suggested. In the
model the additional adsorption of oxygen due to a capture of
electrons at the grain-boundary states is assumed. Accordingly,
the barrier height is increased and current is saturated.
Calculated current-voltage dependences correspond experimentally
observed ones.