Magnesium-based thermoelectric conversion material, magnesium-based thermoelectric conversion element, thermoelectric conversion device, and method for manufacturing magnesium-based thermoelectric conversion material

A magnesium-based thermoelectric conversion element, comprising:

• a magnesium-based thermoelectric conversion material;
• and
• electrodes joined to one surface and the other surface, facing the one surface, of the magnesium-based thermoelectric conversion material,
• wherein the magnesium-based thermoelectric conversion material includes:
• a first layer formed of Mg2Si;
• and
• a second layer formed of Mg2SixSn1-x, wherein x is greater than 0 and less than 1,
• wherein the first layer and the second layer are directly joined to each other,
• within a junction surface with the first layer and in a range equal to or greater than 1 μm and equal to or smaller than 50 μm in a lamination direction from the junction surface, the second layer has a tin concentration transition region in which a tin concentration increases as a distance from the junction surface increases, and
• a region in which the Sn concentration is 0.5% by mass to Y % by mass is regarded as the tin concentration transition region, and Y represents a value which equals 95% of a Sn concentration of the second layer.