2. Introduction

Thermoelectric coupled phenomena are traditionally divided into two categories, depending on whether they occur entirely within the material or involve a vacuum barrier.

In the first case, we are talking about thermoelectricity, while in the second, we are referring to thermoelectric emission (sometimes incorrectly referred to as thermionic emission). We will see that the physical processes involved are actually very similar and that both can even be used in the same system.

Thermoelectric effects were discovered a long time ago; in 1821, the Prussian physicist Seebeck noticed that a magnetized needle was deflected when placed near a circuit formed by two different conductors whose junctions were not at the same temperature (figure 1...