Design, Synthesis And Properties Of N-type Bi₂Te₃/Ba_yNi_xCo_4-xSb₁₂ Graded Thermoelectric Material

In this paper, firstly, filled skutterudite compounds Ba_yNi_xCo_4-xSb₁₂ are prepared by solid reaction. The compact blocks are obtained by Sparkle Plasma Sintering (SPS). The junction temperature of graded Bi₂Te₃/Ba_0.35Ni_0.1Co_3.9Sb₁₂ thermoelectric material was optimized based on the thermoelectric transport properties of monolithic materials, also the length ratio of monolithic materials Bi₂Te₃ and Ba_0.35Ni_0.1Co_3.9Sb₁₂ were optimized in theory when graded materials were used in the temperature difference ranging from 300K to 800K. The n-type graded Bi₂Te₃/Ba_0.35Ni_0.1Co_3.9Sb₁₂ thermoelectric material was prepared by two-step SPS, and the thermoelectric properties of the n-type graded Bi₂Te₃/Ba_0.35Ni_0.1Co_3.9Sb₁₂ thermoelectric material were investigated.Some conclusions have been drawn in the present work as follows:1. The thermoelectric properties and the transport properties of the compounds Ni_xCo_4-xSb₁₂ were optimized, and the greatest dimensionless thermoelectric figure of merit value of 0.48 was obtained at 800K for the compound Ni_0.4Co_3.6Sb₁₂.2. The thermoelectric properties and the transport properties of the compounds Ba_yNi_xCo_4-xSb₁₂ were optimized, and the greatest dimensionless thermoelectric figure of merit value of 0.56 was obtained at 800K for the compoundBa_0.35Ni_0.1Co_3.9Sb_12.3. The junction temperature optimized by the relationship between figure-of-merits of monolithic materials and temperature is about 630K.4. According to the thermal properties of monolithic materials Bi₂Te₃ and Ba_0.35Ni_0.1Co_3.9Sb₁₂, the optimized result is that the optimal length ratio of Bi₂Te₃ and Ba_0.35Ni_0.1Co_3.9Sb₁₂ is about 5.5:10 when it was used in the temperature difference from 300K to 800K.5. The graded Bi₂Te₃/Ba_0.35Ni_0.1Co_3.9Sb₁₂ and Bi₂Te₃/Pd/Ba_0.35Ni_0.1Co_3.9Sb₁₂ thermoelectric material was prepared by two-step SPS. The analysis result of the SEM revealed that junction appearance of the graded Bi₂Te₃/Ba_0.35Ni_0.1Co_3.9Sb₁₂ thermoelectric material is excellent, but Bi2Te3/Pd/Bao.35Nio.iCo3.9Sbi2 is bad, which show Pd is not the optical material.6. The internal resistance, average Seebeck coefficient and power output were calculated by theory model. We finded that the average Seebeck coefficient of graded material possess higher values over a wide temperature difference, and the calculated maximum power outputs of graded material is about 22mW when the loaded is fixed at 0.1Ω, which is about 1.8 times than that of Ba_0.35Ni_0.1Co_3.9Sb₁₂ compound(12mW).