The oxygen transport membrane is a system being developed by St Andrews in conjunction with industry, which at high temperatures will allow the selective migration of oxygen from air to an environment containing a fuel gas, such as hydrogen or carbon monoxide. The system is based upon thin membranes of a mix of ceramic materials, held at high temperatures. These materials often undergo expansion and change in their electrical conductivity in fuel gases. They also tend to degrade in performance at high temperatures. The object of the work being proposed is to understand the relationship between the expansion, conductivity, operating temperatures and oxidising potential of the fuel gas.