With the proposed experiment we aim to perform pair distribution function (PDF) analyses on 16 samples belonging to the Ce1-x(Nd0.74Tm0.26)xO2-x/2 and the Ce1-x(Nd0.63Dy0.37)xO2-x/2 systems (x= 0.05-0.60). PDF analyses will be performed to gain information on the local structure of the present systems, trying to unravel the non-trivial relationship between their ionic conductivity and local structure. In fact, in Ce1-xRExO2-x/2 systems (RE= trivalent rare earth ion), the high ionic conductivity observed between 673 and 973 K at low dopant amount is strictly related to the structural properties, even at the local scale, and to the occurrence of defect aggregates. Consequently, an in-depth structural study is fundamental to evaluate the chemical nature and the amount of the doping ions giving rise to the most efficient electrolytes for a possible application in solid oxide cells working at the intermediate temperature range.