Electronic Conductivity in Nanocrystalline Ce_(0.9)Gd_(0.1)O_(1.95)Thin Films at High Oxygen Partial Pressures

摘要

Gadolinium doped cerium oxide (Ce_(0.9)Gd_(0.1)O_(1.95)) thin films with different microstructure (epitaxial vs. nanocrystalline) were investigated by impedance spectroscopy in oxidizing conditions. As expected, with increasing grain boundary density the ionic conductivity decreased significantly. In addition to this, the sample with the smallest average grain size (10 nm) exhibited a remarkable electronic conductivity (25% of the total conductivity) at an oxygen partial pressure of 10~(-5) bar and temperature of 280℃ despite the large dopant content. This at first surprising result can be fully explained in the framework of the space charge model.