Elastic and thermodynamic properties of the shape-memory alloy AuZn

The current work reports on the elastic shear moduli, internal friction, and the specific heat of the B2 cubic ordered alloy AuZn as a function of temperature. Measurements were made on single-crystal and polycrystalline samples using Resonant Ultrasound Spectroscopy (RUS), semi-adiabatic calorimetry and stress-strain measurements. Our results confirm that this alloy exhibits the shape-memory effect and a phase transition at 64.75 K that appears to be continuous (second-order) from the specific heat data. It is argued that the combination of equiatomic composition and a low transformation temperature constrain the chemical potential and its derivatives to exhibit behavior that lies at the borderline between that of a first-order (discontinuous) and a continuous phase transition. The acoustic dissipation does not peak at the transtion temperature as expected, but shows a maximum well into the low-temperature phase. The Debye temeprature value of 219 K, obtained from the low-temperature specific heat data is in favorable agreement with that determined from the acoustic data (207 K) above the transition.Comment: 25 pages, 6 figures, submitted to Phys. Rev.

Thermophysics of the lanthanide trihydroxides IV. The heat capacity of Ho(OH)3 from 11 to 350 K. Lattice and Schottky contributions

From values of the heat capacity of microcrystalline Ho(OH)3 determined by precise adiabatic calorimetry from 11 to 350 K, the Schottky contribution associated with the Stark splitting of the ground J-manifold (5I8) was resolved by means of an extrapolation of the known lattice heat-capacity variation between La(OH)3 and Gd(OH)3. This calorimetrically deduced Schottky contribution is compared with that calculated from spectroscopically derived energy levels of Ho3+ doped Y(OH)3. Because the lattice parameters of Y(OH)3 and Ho(OH)3 are nearly identical it is assumed that the electronic energy levels of the Ho3+ ions are the same in either host lattice. These results together with independent heat-capacity measurements made at lower temperatures were used to adjust the low-temperature thermophysical functions to evaluate Cp/R, So/R, and -["Go - Ho(0)'/RT], at 298.15 K as 13.80, 15.64, and 7.855.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24580/1/0000863.pd