Bridgman-grown i-Al68.9Pd21.6Mn9.5 quasicrystal: Comparison of α, CP, σ, and χ with those for flux-grown samplesPhysical Review B
AbstractThermal expansivity (α, 1–300 K), heat capacity (CP, 1–108 K), electrical conductivity (σ, 1–300 K) and magnetic susceptibility (χ, 1–300 K) data have been obtained for a Bridgman-grown single grain i-Al68.9Pd21.6Mn9.5 quasicrystal (BR) for direct comparison with data previously published for a flux-grown single grain sample [ Phys. Rev. B 65 184206 (2002)], and present σ, χ and CP data for a second flux-grown sample described in an earlier publication [ Philos. Mag. B 79 1673 (1999)]. Fortuitously, comparative analyses show these samples to have essentially the same composition. At all temperatures, σ and χ for BR are, respectively, approximately one-third and one-quarter those for PRB. The CP’s are the same (±1%) down to 30 K, below which the BR CP decreases more rapidly to one-half that for PRB at 1 K. The α’s agree to ±2% from 300 to 40 K, with a more rapid decrease for BR below 30 K, eventually to 0.6 αPRB below 4 K. The total Grüneisen parameters are similar at all temperatures. The two methods for sample growth differ primarily in a quenching of the flux-grown sample to room temperature after growth, while the Bridgman-grown sample cools very slowly, resulting in slightly different phases, and magnetic properties which are associated with lattice defects. An attempt to convert the single grain flux-grown sample to the phase of the Bridgman sample using an 800°C anneal and a slow cool to room temperature was not successful, with the appearance of second phase inclusions. These inclusions are ascribed to slightly different compositions for the two phases [ Boissieu et al. Philos. Mag. A 78 305 (1998)]. This suggests that a single grain flux-grown sample with an Mn composition near 9% cannot be converted by annealing and slow cooling into a single grain LT phase, and vice versa. These considerations may not apply to samples with Mn compositions closer to 8%.
Copyright OwnerAmerican Physical Society
Citation InformationClayton A. Swenson, Thomas A. Lograsso, N. E. Anderson and A. R. Ross. "Bridgman-grown i-Al68.9Pd21.6Mn9.5 quasicrystal: Comparison of α, CP, σ, and χ with those for flux-grown samples" Physical Review B Vol. 70 Iss. 9 (2004) p. 094201
Available at: http://works.bepress.com/thomas_lograsso/133/