Thermoelectric conversion element

A thermoelectric conversion element converting heat into electricity, comprising:

• a thermoelectric conversion material portion constituted of a compound semiconductor that is composed of a first base material element A and a second base material element B and is represented by Ax-cBy with a value of x being smaller by c with respect to a compound AxBy according to a stoichiometric ratio;
• a first electrode disposed in contact with the thermoelectric conversion material portion;
• and
• a second electrode disposed in contact with the thermoelectric conversion material portion and apart from the first electrode;
• an A-B phase diagram including
• a first region corresponding to a low temperature phase,
• a second region corresponding to a high temperature phase, and
• a third region corresponding to a coexisting phase, sandwiched between the low temperature phase and the high temperature phase, in which the low and high temperature phases coexist,
• a temperature at a boundary between the first region and the third region changing monotonically with a change in c.