2. Thermoelectric materials

The first thermoelectric devices, which appeared in the second half of the 19th century, used metals and alloys such as constantan, discovered in 1890 and still used in thermocouples today. However, their low Seebeck coefficients and high thermal conductivities limited their efficiency. A major breakthrough came when Abram Ioffe identified doped semiconductors as more suitable materials. Shortly after 1945, a generator based on PbS and ZnSb achieved 5% efficiency under a 400 K thermal gradient. In the 1950s, Bi ₂ Te ₃ became the benchmark at near ambient temperature, while PbTe dominated between 400 and 800 K and Si-Ge alloys, introduced in the early 1960s, were used at high temperatures (> 800 K) [