Detail investigation of thermoelectric performance and magneticproperties of Cs‑doped Bi_2Sr_2Co_2O_y ceramic materials

摘要

Bi_2Sr_(2−x）Cs_xCo_2O_y materials with 0 ≤ x ≤ 0.15, have been fabricated via the classical ceramic technique. XRD results haveindicated that undoped and Cs-substituted samples are composed of Bi_2Sr_2Co_2O_yphase as the major one. Microstructuralstudies have demonstrated the formation of a liquid phase, which allows a drastic grain growth. This factor is responsiblefor a drastic improvement of relative density, reaching about 95% of the theoretical one for 0.125 Cs content. On theother hand, electrical resistivity has been reduced up to 14 mΩ cm at 650 °C for 0.125 Cs content, around 40% lower thanthe obtained in undoped samples. As a consequence, Seebeck coefficient has been decreased due to the raise in chargecarrier concentration. The highest power factor at 650 °C (0.21 mW/K~2 m) has been found for 0.125 Cs substituted sample,about 40% larger than the obtained in undoped samples, and very similar to the notified in single crystals (0.26 mW/K~2m). Magnetisation with respect to temperature results have demonstrated that measured samples have a paramagneticproperty above 50 K, except 0.10 Cs. Magnetic hysteresis curves have shown that the slopes and the magnitudes haveincreased with decreasing temperature.