Electrical Conductivity and Phase Transition of Solid Oxide Fuel Cell Electrolyte La2Mo2-xTixO9-δ Ceramics

A novel series of ceramic samples La2Mo2-xTixO9-δ (x = 0, 0.025, 0.05, 0.075) were prepared by solid-state reaction method. Their structures and phase transitions were studied by XRD, DSC and CTE. Their Electrical conductivities and oxygen ion transport numbers were measured by AC impedance spectroscopy at 773~1073 K and EMF at 673~1073 K, respectively. Results showed that even when x=0.075, the sample was almost pure oxygen ion conductor under the oxygen partial pressure gradient of 1.0 atm/0.21 atm, and though all the Ti-doped samples still underwent α/β structure transition, no abrupt change in the electrical conductivity was observed accompanying with the transition. They exhibited considerably higher electrical conductivity than La2Mo2O9, especially at 773~873 K and the conductivity increased with increasing x value. The value of conductivity for La2Mo1.925Ti0.075O9-δ reached 8.5×10-3 S•cm-1 at 773 K and 0.08 S•cm-1 at 1,073 K.