Ionic Conduction and Two Carrier Types. In certain materials, particularly at higher temperature, positive ions can move throughout the sample in response to applied electric fields, resulting in what is known as ionic conduction. Since this conduction is typically poor, it is mainly observable in materials where there are no free electrons that would transport current. However, occasionally it can occur that a material has both electrical conduction and ionic conduction of roughly the same magnitude – such materials are known as mixed ion-electron conductors. Suppose free electrons have density ne and scattering time τe (and have the usual electron mass me and charge −e). Suppose that the free ions have density ni , scattering time τi , mass mi and charge +e. Using Drude theory,
(1) Calculate the electrical resistivity.
(2) Calculate the thermal conductivity.
(3) Calculate the Hall resistivity.