Thermal conductivity in XIZ Heusler type intermetallic compounds

Results are given of comprehensive measurements on thermal conductivity of Heusler type intermetallic compounds Fe₂AlTi, Co₂AITi, Ni₂AlTi, Ni₂GaTi, Ni₂AlZr and Ni₂AlHf. The compounds have fully ordered L2₁ structure. There exists a wide single phase region of L2₁ in Ni-Al-Ti ternary alloy system. The contour map showing the magnitude of thermal conductivity is constructed in Ni₂AlTi single phase region. The thermal conductivity in Ni₂AlTi takes a maximum of 21.4 Wm^-1K^-1 at stoichiometry which is much lower than that of NiAl having a B2 structure. By the deviation from stoichiometry, the thermal conductivity decreases in Heusler compounds. The magnitude of thermal conductivity in Fe₂AITi, Co₂AlTi and Ni₂AlTi are compared in connection with those of B2 aluminides (FeAl, CoAl, NiAl) and titanides (FeTi, CoTi, NiTi). Thermal conductivities in three kinds of Heusler compounds X²AfTi(A': Fe, Co, Ni) are almost the same value of approximately 20 Wm^-1 K^-1. Ordering from B2 to L2₁ increases thermal conductivity in accord with the estimation by Nordheim relation. The magnitude of thermal conductivity in X₂YZ Heusler compounds, including Ni₂GaTi, Ni₂AlZr and Ni₂AlHf, is related to those of AT and XZ compounds having a B2 structure.