THERMAL-CONDUCTIVITY IN X(2)YZ HEUSLER TYPE INTERMETALLIC COMPOUNDS

Results are given of comprehensive measurements on thermal conductivit y of Heusler type intermetallic compounds Fe3AlTi, Co2AlTi Ni2AlTi, Ni 2GaTi, Ni2AlZr and Ni2AlHf. The compounds have fully ordered L2(1) str ucture. There exists a wide single phase region of L2(1) in Ni-Al-Ti t ernary alloy system. The contour map showing the magnitude of thermal conductivity is constructed in Ni2AlTi single phase region. The therma l conductivity in Ni2AlTi takes a maximum of 21.4 Wm(-1)K(-1) at stoic hiometry which is much lower than that of NiAl having a B2 structure. By the deviation from stoichiometry, the thermal conductivity decrease s in Heusler compounds. The magnitude of thermal conductivity in Fe2Al Ti, Co2AlTi and Ni2AlTi are compared in connection with those of B2 al uminides (FeAl, CoAl, NiAl) and titanides (FeTi, CoTi, NiTi). Thermal conductivities in three kinds of Heusler compounds X(2)AlTi (X: Fe, Co , Ni) are almost the same value of approximately 20 Wm(-1)K(-1). Order ing from B2 to L2(1) increases thermal conductivity in accord with the estimation by Nordheim relation. The magnitude of thermal conductivit y in X(2)YZ Heusler compounds, including Ni2GaTi, Ni2AlZr and Ni2AlHf, is related to those of XY and XZ compounds having a B2 structure.