Electron Transport Properties and Thermoelectric Effect of Al-Pd-Mn Single Quasicrystals Doped with M=Au or Re by ion Im
- PDF / 68,924 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 50 Downloads / 113 Views
Electron transport properties and thermoelectric effect of Al-Pd-Mn single quasicrystals doped with M=Au or Re by ion implantation and its comparison with quaternary quasicrystalline samples. V. Fournée a,d, U.Mizutani a, T.Takeuchi a K.Saitoh b, M.Ikeyama b, J.Q. Guo c,A.P. Tsai c a Department of Crystalline Materials Science, Nagoya University, Japan b National Industrial Research Institute of Nagoya, Nagoya, Japan c National Research Institute for Metals, Tsukuba, Japan d Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA Abstract Ion implantation experiments were carried out on a single grain Al-Pd-Mn icosahedral quasicrystal. The influence of Re or Au dopant on the thermopower and the electrical resistivity has been measured. Comparison with ternary and quaternary alloys produced by usual metallurgical techniques is made. The results indicate that the efficiency of this quasicrystalline alloy as a thermoelectric material can be improved by adjusting composition and structural quality, as well as by the addition of a small amount of Re, whereas Au implantation is inefficient in that respect. 1.Introduction Among the surprising properties of quasicrystals (QC) are the large values of the thermopower and the low thermal conductivity which have been measured in several Al-Transition Metals ternary systems. These two properties combine efficiently and, eventually, could lead to the use of QC as a new class of materials for thermoelectric (TE) applications. The potential of any given material as a TE is evaluated by its figure of merit Z, which is defined as ZT= S2σT/(κe + κl). Here, S defines the thermopower (or Seebeck coefficient), σ is the electronic conductivity, T is the absolute temperature and κe and κl are the electronic and lattice part of the thermal conductivity respectively. In order to compete with commercially used TE, like Bi-Te or Si-Ge alloys, a value of ZT of the order of unity must be achieved. In this article, we will describe an attempt to improve Z in an Al-Pd-Mn QC by adding a very small amount of a fourth element into this ternary system. In doing so, our strategy is to get a significant increase in the thermopower without affecting too much the value of the electronic conductivity. We will further make the assumption that the thermal conductivity will not be affected, and could be even reduced, by the addition of a dopant element, because this results in an increase in the mass scattering. The process by which minute amount of dopants was introduced into the ternary quasicrystalline matrix is described in the next section. The ion implantation method was selected because it provides a unique way to obtain a very homogeneous distribution of dopants. The resulting effects on the transport properties are described in section 3 and compared to that obtain on Al-Pd-Mn-Re quaternary alloys prepared by usual metallurgical techniques.
K14.3.1
2. Experiments Alloy preparation. The ion implantation experiments were performed on a single grain QC prepared by the floating zone method, with
Data Loading...
