Samples were densified using CPS se

Samples were densified using CPS setup. Only the sample containing 7 wt% PTFE does not show a good mechanical stability, so it cannot be used for further characterizations. However, the other samples containing from 0 to 5 wt% PTFE are solid mechanically stable (they can be handled without specific precaution, which is not the case of the sample containing 7 wt% PTFE, crumbling easily when manipulated), so they could be electrically measured. Their structure characterization was performed on samples using XRD, and profile refinements show no evolution of lattice parameters (table 1), confirming the preservation of ZnO wurtzite structure, with less than 0.02% difference in a and c lattice parameters between all samples.