The current state-of-the-art solid oxide fuel cell (SOFC) electrolyte material, 8 mol% yttria stabilised zirconia (8YSZ), exhibits good performance at temperatures above 850 °C. Scandia-stabilised zirconia (SSZ) offers much higher ionic conductivity than YSZ, but there are questions about high cost and long-term stability of this material. Our recent work on (Mg, In) co-doped SSZ showed an increase in ionic conductivity with annealing time. This is unusual as in general, ionic conductivity usually decreases with time due to ordering of mobile species. The mechanism of this increased conductivity remains poorly understood but we observed diffuse scattering in our electron diffraction pattern, which we believe is due to the short-range ordering of oxygen/vacancies. Therefore, we request 4 days of beam-time on Polaris to carry out a combined PDF-ac impedance spectroscopy experiment.