Hello Thomas Breuer, thank you for answering me.

The shape of the sample is cylindrical pressed powder (6mm diameter per 5mm height) it is zirconia tetragonal stabilized with 3% mol of yttria.

I am using platinum wires to apply the voltage. So there is also the platinum resistance that should be growing with the temperature, while the zirconia resistance is falling with the temperature.

I'm thinking of make two experiments, first touch the platinum wires and measure their resistance vs temperature. Then measure the resistance of the zirconia+platinum in the system. Then I subtract the platinum resistance from the zirconia + platinum to acquire only the zirconia resistance, what do you think about it?

Thank you, once again.

Thank you very much, I will do that!