Formation of FePd<SUB>3</SUB> Superlattice in Fe-80 at%Pd Alloys with Additions of the Third Elements

The effect of additional elements of Fe-80 at%Pd alloys on the formation of L12 type superlattice has been investigated by X-ray diffraction, transmission electron microscopy, and thermoelectric power and electrical resistivity measurements. FePd3 superlattice (L12 type) is found to form in the Fe-80 at%Pd alloy (A1 type) containing Mn, Al, In and Ga up to about 8 at%. Electron diffraction patterns of Fe-80 at%Pd alloys containing 4∼6.5 at%Al show superlattice reflections in addition to the fundamental reflections, and the dark field images by transmission electron microscopy exhibit the formation of ordered domain structures. The ordered domain size increases with increasing concentration of Al element. The order-disorder transition temperature, TC, is found on the curves of the thermoelectric power and electrical resistivity versus temperature of Fe-80 at%Pd alloys added Al element. The thermoelectric power and the electrical resistivity of these alloys increase with the form of FePd3 superlattice on ordering. Form these experimental results, the formation of FePd3 superlattice in the Fe-80 at%Pd alloys can be qualitatively explained by the Brillouin Zone effect.