Cathodes based on K₂NiF₄ phases have been shown as high performance cathodes for solid oxide fuel cells (SOFC). The main candidate in this family is La₂NiO_4+δ (LNO) which is known to have high electronic conductivity, high ionic conductivity and good surface exchange at low temperatures (500-600°C). However, performance of these cathodes needs further improvement to compete with the high temperature cathodes such as La_xSr_1-xMnO₃ (LSM). An increase in the surface exchange is expected by replacing Ni with a low amount of Mn, however such a replacement is not stable and Sr needs to replace the La in the A site to compensate for the small Mn ion. Samples with varying Sr content have been produced using a citric acid sol gel route and their electrical properties have been studied. Changing the Mn:Sr ratio induced a change in the lattice parameters and as such affected properties of the material. The biggest change was an increase in the electronic conductivity across the solid solution range of 10-50% Sr. However, while the 10% sample behaves very similarly to LNO despite having much lower electronic conductivity, Sr segregation in the high Sr content samples, shown using XPS, has some detrimental effects on the cathode behaviour. The correlation between the structure, electronic conductivity, Sr segregation and impedance results will be presented.