Abstract

This paper describes the design, manufacturing and characterization of newly developed mixed thick-/thin film thermoelectric microgenerators based on magnetron sputtered constantan (copper-nickel alloy) and screen-printed silver layers. The thermoelectric microgenerator consists of sixteen thermocouples made on a 34.2 × 27.5 × 0.25 mm3 alumina substrate. One of thermocouple arms was made of magnetron-sputtered constantan (Cu-Ni alloy), the second was a Ag-based screen-printed film. The length of each thermocouple arm was equal to 27 mm, and their width 0.3 mm. The distance between the arms was equal to 0.3 mm. In the first step, a pattern mask with thermocouples was designed and fabricated. Then, a constantan layer was magnetron sputtered over the whole substrate, and a photolithography process was used to prepare the first thermocouple arms. The second arms were screen-printed onto the substrate using a low-temperature silver paste (Heraeus C8829A or ElectroScience Laboratories ESL 599-E). To avoid oxidation of constantan, they were fired in a belt furnace in a nitrogen atmosphere at 550/450 °C peak firing temperature. Thermoelectric and electrical measurements were performed using the self-made measuring system. Two pyrometers included into the system were used for temperature measurement of hot and cold junctions. The estimated Seebeck coefficient, α was from the range 35 − 41 µV/K, whereas the total internal resistances R were between 250 and 3200 ohms, depending on magnetron sputtering time and kind of silver ink (the resistance of a single thermocouple was between 15.5 and 200 ohms).

Highlights

  • Small and cost-effective thermoelectric microgenerators based on the Seebeck effect in semiconductors or metals usually convert waste thermal energy directly into useable electrical energy.They are potential energy sources for low-power autonomous microsystems

  • The most commonly investigated thermoelectric materials, sensors and microgenerators are based on metals, materials based on silicon and/or germanium (SiGe, silicides, germanides), Bi2 Te3, materials based on elements from group V (As, Sb, Bi) and group VI (Se, Te), PGEC materials, e.g., skutterudites, intermetallic clathrates or half-Heusler alloys), TAGS (Te-Ag-Ge-Sb) or LAST

  • This paper describes the design, fabrication and characterization of newly developed, costeffective thermoelectric microgenerators based on magnetron-sputtered constantan

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Summary

Introduction

Small and cost-effective thermoelectric microgenerators based on the Seebeck effect in semiconductors or metals usually convert waste thermal energy directly into useable electrical energy. They are potential energy sources for low-power autonomous microsystems. On the other hand, mixed (thick/thin) film microgenerators fabricated and investigated at the Wrocław University of Science and Technology, where one arm was made from a screen-printed Ag- or Ni-based metallic film and the second one was made from magnetron-sputtered germanium-doped films [18,36,37,38], had a larger effective Seebeck coefficient, but simultaneously exhibited a much larger internal resistance, causing a lower power output compared to thick-film metallic microgenerators

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