Fabrication of Multilayer-Type Mn-Si Thermoelectric Device

This research aims to develop a direct-contact manganese silicon p / n multilayer-type thermoelectric power generation block. p -type MnSi 1.74 and n -type Mn 0.7 Fe 0.3 Si 1.68 ball-milled powders with diameter of about 10 μ m or less were mixed with polyvinyl butyl alcohol diluted with methylbenzene at pigment volume concentration of approximately 70%. The doctor-blade method produced 45- μ m-thick p - and n -type pigment plates. The insulator, i.e., powdered glass, was mixed with cellulose to form insulator slurry. Lamination of manganese silicide pigment layers and screen-printed insulator layers was carried out to fabricate multilayer direct-contact thermoelectric devices. Hot pressing and spark plasma sintering were carried out at 450°C and 900°C, respectively. Four to 30 thermoelectric (TE) p / n pairs were fabricated in a 10 mm × 10 mm × 10 mm sintered TE block. The maximum output was 11.7 mW/cm 2 at a temperature difference between 20°C and 700°C, which was about 1/85 of the ideal power generation estimated from the thermoelectric data of the bulk MnSi 1.74 and Mn 0.7 Fe 0.3 Si 1.68 materials. A power generation test using an engine test bench was also carried out.