... It is sometimes called the `thermoelectric figure-of-merit,' although this name is more often given to the dimensionless combination ZT sS 2 T X K In the above formulas, s, S, and K are respectively the material electrical conductivity, thermopower (Seebeck coefficient), and thermal conductivity, and T is the operating temperature or the average temperature T1 T2 a2 of the converter, with T1 and T2 being the respective cold and hot end temperatures. ... We first consider the thermal conductivity. ...