b-Ag 2 Se is a narrow-bandgap semiconductor with a high electrical conductivity, reasonably large Seebeck coefficient, and low thermal conductivity. It is regarded as a potential candidate for thermoelectric applications. In this work, we prepared powders of b-Ag 2 Se by hydrothermal reaction at 180°C. The spark plasma sintering technique was employed to form compact samples. The thermoelectric properties were measured in a temperature range between 20 K and 350 K. A maximum figure of merit of over 0.6 was found around room temperature. Theoretical calculations were carried out to estimate the Seebeck coefficient of b-Ag 2 Se, reproducing the experimental trend qualitatively.

No abstract

A multi-element and multi-phase internal oxidation model that couples thermodynamics with kinetics is developed to predict the internal oxidation behaviour of Fe-Mn-Cr steels as a function of annealing time and oxygen partial pressure. To validate the simulation results, selected Fe-Mn-Cr steels were annealed at 950°C for 1-16 h in a gas mixture of Ar with 5 vol% H 2 and dew points of -30, -10 and 10°C. The measured kinetics of internal oxidation as well as the concentration depth profiles of internal oxides in the annealed Fe-Mn-Cr steels are in agreement with the predictions. Internal MnO and MnCr 2 O 4 are formed during annealing, and both two oxides have a relatively low solubility product. Local thermodynamic equilibrium is established in the internal oxidation zone of Fe-Mn-Cr steels during annealing and the internal oxidation kinetics are solely controlled by diffusion of oxygen. The internal oxidation of Fe-Mn-Cr steels follows the parabolic rate law. The parabolic rate constant increases with annealing dew point, but decreases with the concentration of the alloying elements.