Formation of sol-gel derived (Cu,Mn,Co)3O4 spinel and its electrical properties

An (Mn,Co)3O4 spinel layer effectively suppresses Cr outward diffusion, but the occurrence of spallation between coating and metal interfaces and the increasing oxidation rate over time significantly deteriorate cell performance. A transition metal cation, particularly Cu, is added into the (Mn,Co)3O4 to improve the long-term stability of the interconnect materials for low-to-intermediate-temperature solid oxide fuel cells (SOFCs). In this work, fine-crystalline (Cu,Mn,Co)3O4 spinel powders with an average crystallite size of 21 nm were successfully synthesized via the citric acid-nitrate method. The potential for use as a coating material for low-to-intermediate-temperature SOFC interconnects was explored. According to the TG curves, IR spectra, and XRD patterns, 800 °C is recommended as the minimum calcination temperature for (Cu,Mn,Co)3O4 spinel materials. Compared with (Mn,Co)3O4 spinel materials, the addition of Cu does not induce significant changes in the crystal structure but markedly improves the electrical conductivity (116 Scm−1) and the activation energy (0.394 eV) of the (Cu,Mn,Co)3O4 spinel. Overall, the sol-gel derived (Cu,Mn,Co)3O4 spinel can be used as a coating material for low-to-intermediate-temperature SOFC interconnects and is superior to (Mn,Co)3O4 spinel because high electrical conductivity is preferred to minimize ohmic losses between the electrodes of adjacent cells.