The sintering of ZnO–Ag2 O was performed during 1 h at temperature 1170 K which is below the melting temperature of silver. The independent repetition of the sintering of samples with different amount of Ag2O addition gave reproducible parameters. For the electrical measurements
Ag electrodes at the same plane surface or at the opposite plane surfaces were obtained. Additionally, ZnO–Ag2O, ZnO–CoO, ZnO–CuO (0.5 at% of added metal) and pure