Electrical properties of approximant phases in Al-Pd-(Fe, Ru) systems

X-ray diffraction patterns of structurally ordered 1/0 cubic approximant ph ases in the Al-Pd-(Fe, Ru) ternary systems are presented. The 1/0 approxima nt in the Al-Pd-Fe system was found to possess a body-centered lattice with a = 15.3 Angstrom, whereas that in the Al-Pd-Ru system a face-centered one with a = 15.5 Angstrom, and the results were compared with the reported st ructural models. Their electrical resistivities have been investigated and found to be substantially high for the lowest order approximants: rho (300 K) similar to 1000 mu Omega cm. In addition, negative temperature coefficie nts accompanied by a distinctive resistivity maximum in the rho -T curves h ave been observed. The peculiar rho -T dependences will be described in ter ms of the quantum interference effects with strong spin-orbit scattering an d it will be shown that the transport properties of 1/0 approximants are qu ite sensitive to disorder reflecting the flexibility of their structure. (C ) 2000 Elsevier Science B.V. All rights reserved.