Thermoelectric conversion material

A thermoelectric conversion material made of p-type or n-type full-Heusler alloy represented by a composition formula (Chemical Formula 1) below:

• (Fe1-xM1x)2+σ(Ti1-yM2y)1+φ(A1-zM3z)1+ω (Chemical Formula 1),
• wherein the A is at least one element selected from a group including Si and Sn,
• the M1 and the M2 are at least one element selected from a group including Cu, Nb, V, Al, Ta, Cr, Mo, W, Hf, Ge, Ga, In, P, B, Bi, Zr, Mn, and Mg,
• the M3 is at least one element selected from a group including Cu, Nb, V, Al, Ta, Cr, Mo, W, Hf, Ge, Ga, In, P, B, Bi, Zr, Mn, Mg, and Sn,
• when the σ, the φ, and the ω satisfy a relation σ+φ+ω=0, and
• the x, the y, and the z satisfy relations x=0, y=0, and z=0, respectively, contents of Fe, Ti, and A in the alloy represented by the composition formula (Chemical Formula 1) are u at %, v at %, and w at %, respectively, and
• when a composition of the alloy in a ternary phase diagram of Fe—Ti-A is represented by a point (u, v, w),
• the point (u, v, w) is located in a region inside a hexagon having points (50, 37, 13), (45, 30, 25), (39.5, 25, 35.5), (50, 14, 36), (54, 21, 25), and (55.5, 25, 19.5) as apexes in the ternary phase diagram,
• when the valence electron number of the M1 is m1,
• the valence electron number of the M2 is m2, and
• the valence electron number of the M3 is m3,
• an average valence electron number per atom VEC in the full-Heusler alloy is represented by a mathematical formula (Mathematical Formula 1) below:
• VEC(σ,x,φ,y,ω,z)=[{8×(1−x)+m1×x}×(2+σ)+{4×(1−y)+m2×y}×(1+φ)+{4×(1−z)+m3×z}×(1+ω)]/4 (Mathematical Formula 1)
• as a function of the σ, the x, the φ, the y, the ω, and the z, and
• ΔVEC represented by a mathematical formula (Mathematical Formula 2) below:
• ΔVEC=VEC(σ,x,φ,y,ω,z)−VEC(σ,0,φ,0,ω,0) (Mathematical Formula 2)
• satisfies a relation 0.2<|ΔVEC|≤0.3.

A thermoelectric conversion material made of p-type or n-type full-Heusler alloy,

• wherein the full-Heusler alloy contains Fe, Ti, and A (A is at least one element selected from a group including Si and Sn) as main components,
• the full-Heusler alloy contains Cu and V,
• a content of Cu in the full-Heusler alloy is greater than 0 at % and 1.75 at % or less, and
• a content of V in the full-Heusler alloy is 1.0 at % or more and 4.2 at % or less.