Thermoelectric conversion material, thermoelectric conversion module, and production method of thermoelectric conversion material

A thermoelectric conversion module comprising:

• a thermoelectric conversion unit;
• and
• a first electrode and a second electrode which electrically and thermally contact the thermoelectric conversion unit, wherein
• at least a part of the thermoelectric conversion unit is formed of a thermoelectric conversion material,
• the thermoelectric conversion material includes a main phase and a grain boundary phase,
• the main phase is a Fe2TiSi-based full Heusler alloy,
• the grain boundary phase includes a metal N slightly solid-soluble in Fe2TiSi, and
• a volume ratio of the grain boundary phase is 2% to 10%.

A production method of a thermoelectric conversion material, the method comprising:

• a preparation process of preparing raw material powder of an amorphized Fe2TiSi-based full Heusler alloy, and raw material powder including a metal N;
• a heating process of heating the raw material powder;
• and
• a cooling process of cooling a product material after the heating process, wherein
• a grain boundary phase is formed between main phases of a thermoelectric conversion material formed of the Fe2TiSi-based full Heusler alloy, by precipitating the metal N, and a volume ratio of the grain boundary phase is 2% to 10%.