The conversion kinetics of the Ga " O ' + YSZ samples to NZGO + YSZ was characterized via X-ray diffraction using Cu -. = 1.5406 Å radiation (Bruker, D2 Phaser). Rietveld refinement was conducted using the full-pattern Rietveld method based on least-squares refinement using GSAS II Samples were cross-sectioned using a high precision diamond saw (Allied High Tech) and fine polished to 200 nm (Buehler). After polishing, samples were thermally etched at 100 °C below sintering temperatures for 1h. For SEM imaging (FEI Quanta 600 FEG), polished surfaces were 5 nm carbon coated (Gatan 682 PECS) to reduce the electron charging effect. The grain size was measured by the mean linear intercept method using ImageJ software .