Abstract
Phase relations at subsolidus temperatures as well as at , crystallographic data, electrical and thermal transport measurements, and heat capacity data are reported for several compositions within the clathrate type-I solid solution: (◻ is a vacancy). The solid solution derives from binary clathrate with a solubility limit of 3.8 Pd atoms per formula unit at . Structural investigations throughout the homogeneity region confirm cubic primitive symmetry consistent with the space group type and lattice parameters ranging from for to for . The primary field of clathrate crystallization has been elucidated from micrography and differential thermal analyses. Both heat capacity and inelastic neutron diffraction define a low-lying, almost localized, phonon branch. Studies of transport properties evidence electrons as the majority charge carriers for most of the homogeneity region; however, at the Pd-rich limit, holes dominate the electronic transport. The crossover between both regimes provides appropriate conditions for attractively high Seebeck values. The lattice contribution dominates the overall thermal conductivity.
7 More- Received 6 May 2007
DOI:https://doi.org/10.1103/PhysRevB.76.144118
©2007 American Physical Society