RESUMEN
Owing to the energy and environmental issues, energy recovery technologies attract an increasing interest. Thermoelectric power generation is a recycling technology, which directly converts heat energy into electric energy by reusing waste heat. In this study, n-type Bi2Te2.7Se0.3 thermoelectric materials doped with Cu were fabricated by hot pressing. The Bi-Te system has excellent thermoelectric properties in the middle- and low-temperature ranges; when a certain amount of Cu dopant is added, the thermoelectric properties are improved. The thermoelectric properties of the samples doped with Cu were compared with those of the intrinsic Bi-Te-based sample without Cu doping. In addition, the effects of the Cu concentration on the thermoelectric-material structures were investigated.
RESUMEN
Intrinsic Cu- and Ni-added Cu electrodes were prepared to study Sn-3Ag-0.5Cu lead-free solder joints. Our work focused on three categories: (1) formation and role of intermetallic compounds, (2) structural and compositional change of intermetallic compounds due to thermal aging effects, and (3) mechanical bonding strength of solder joints. A series of SEM, EDX, and bonding test analyses were performed on two electrode types to study joint morphologies, the types of intermetallic compounds formed, and bonding strengths, respectively. As a result, after heat treatments at 150 °C for 10 h, 100 h, and 300 h, Cu6Sn5 and (Ni, Cu)3Sn4 were obtained at the interfaces of the intrinsic Cu electrode and the Ni-added Cu electrode, respectively. In the Ni-added Cu electrode samples, the growth rate of the intermetallic compounds was reduced, but the mechanical bonding strength had a higher value compared to that of the intrinsic Cu electrode. The bonding characteristics under different heat treatment conditions are also discussed.
RESUMEN
Higher manganese silicide is generally used in thermoelectric devices between 700 K and 900 K. MnSi1.73Al0.005 samples were fabricated by two continuous solid-state reactions followed by hot pressing because the electrical conductivity of all the samples is strongly dependent on Al doping, showing superior thermoelectric performance to the as-synthesized higher manganese silicide. The solid-state-reaction was performed at 1173 K for 6 hours. The effects of the sintering temperature were examined by sintering at three different temperatures: 1273 K, 1323 K and 1373 K. For the surface, microstructural, and electrical properties, scanning electron microscopy, X-ray diffraction, and a series of electric conductivity, Seebeck coefficient, and thermal conductivity analyses were conducted, respectively. As a result, the optimal process temperature for Al-doped higher manganese silicide using a hot-press technique was determined.