Improvement of Electrical Contact Between TE Material and Ni Electrode Interfaces by Application of a Buffer Layer

Abstract

A single π-structure thermoelectric (TE) module based on p-type NaCo2O4, n-type Mg2Si, and Ni electrode was fabricated by the spark plasma sintering (SPS) method. The NaCo2O4 powder was synthesized by using a metal–citric acid complex decomposition method. Bulk Mg2Si prepared by melt quenching was ground into a powder and sieved to particle size of 75 μm or less. To obtain a sintered body of NaCo2O4 or Mg2Si, the powder was sintered using SPS. Pressed Ni powder or mixed powder consisting of Ni and SrRuO3 powder was inserted between these materials and the Ni electrode in order to connect them, and electrical power was passed through the electrodes from the SPS equipment. The open-circuit voltage (VOC) values of a single module in which TE materials were connected to the Ni electrodes by using pressed Ni powder was 82.7 mV, and the maximum output current (Imax) and maximum output power (Pmax) were 212.4 mA and 6.65 mW at ΔT = 470 K, respectively. On the other hand, VOC of a single module in which TE materials and an Ni electrode were connected with a mixed powder (Ni:SrRuO3 = 6:4 volume fraction) was 109 mV, and Imax and Pmax were 4034 mA and 109 mW at ΔT = 500 K, respectively. These results indicate that the resistance at the interface between the TE materials and the Ni electrode can be decreased and the output power can be increased by application of a buffer layer consisting of Ni and SrRuO3.