  We theoretically study the thermoelectric response of ionic conductors to an
applied temperaturegradient. As a main result we find that open and closed
systems with respect to charge exchange,result in different expressions for the
thermopower which may even take opposite signs. For theexperimentally most
relevant zero-current steady state, we show that the thermopower of ionic
conductorsdoes not depend on the mobilities, contrary to what is known for
metals and semiconductors.The different behavior of ionic and electronic
conductors is traced back to the unlike conservationlaws for ionic carriers and
electron-hole pairs.
