Reduced ionic conductivity in biaxially compressed ceria

Abstract

Interfacial lattice mismatch strain has been controversially suggested as a means to alter ionic conductivity in solid ion conductors. Here, thin film multilayers composed of yttria-doped ceria (YDC) and Ce_1−xZr_xO₂ (CZO) allow systematic quantification of the effect of biaxial compressive strain on oxygen ion conductivity in ceria. Since the lattice parameter of CZO is highly dependent on the Ce/Zr atomic ratio, its use enables precise control of the strain magnitude in neighboring lattice planes of YDC. Three series of multilayers were fabricated using Ce_0.55Zr_0.45O₂ (CZO45), Ce_0.70Zr_0.30O₂ (CZO30), and CeO₂, with an interfacial lattice mismatch of −2.2%, −1.5%, and near-zero, respectively. The compressive strain in the YDC layers caused fairly drastic reductions in the ionic conductivity. Each 1% increase in compressive strain in the YDC yields a 1.6-fold reduction in interfacial conductivity at 650 °C and a 3-fold reduction at 450 °C. Other interfacial effects, however, were also found to have significant impact on the ionic conduction.