RESUMO
Skutterudite compounds have been studied as potential thermoelectric materials due to their high thermoelectric efficiency, which makes them attractive candidates for applications in thermoelectric power generation. In this study, the effects of double-filling on the thermoelectric properties of the CexYb0.2-xCo4Sb12 skutterudite material system were investigated through the process of melt spinning and spark plasma sintering (SPS). By replacing Yb with Ce, the carrier concentration was compensated for by the extra electron from Ce donors, leading to optimized electrical conductivity, Seebeck coefficient, and power factor of the CexYb0.2-xCo4Sb12 system. However, at high temperatures, the power factor showed a downturn due to bipolar conduction in the intrinsic conduction regime. The lattice thermal conductivity of the CexYb0.2-xCo4Sb12 skutterudite system was clearly suppressed in the range between 0.025 and 0.1 for Ce content, due to the introduction of the dual phonon scattering center from Ce and Yb fillers. The highest ZT value of 1.15 at 750 K was achieved for the Ce0.05Yb0.15Co4Sb12 sample. The thermoelectric properties could be further improved by controlling the secondary phase formation of CoSb2 in this double-filled skutterudite system.
RESUMO
A 29-year-old woman presented with secondary amenorrhea, primary infertility, and virilization, which had developed over the past 2 years was suspected to have a virilizing tumor at her left ovary. Her serum testosterone level was markedly elevated (380 ng/dL). Left salpingoophorectomy was performed, and histopathological examination revealed a thecoma of the left ovary. The postoperative serum testosterone level returned to 65 ng/dL. The patient did not have regression of virilism soon. However, the patient had a normal menstruation 29 days after surgery and gave birth to a baby 13 months after surgery.
