High thermoelectric performance of NaF-doped Bi2Ca2Co2Oy ceramic samples

Abstract

In this study, Bi2-xNaxCa2Co2Oy-xFx (x = 0.0, 0.1, 0.2, and 0.3) ceramic samples were synthesized using a combination of high-energy ball milling and hot pressing sintering methods. The effects of NaF on the structure and thermoelectric performance of Bi2Ca2Co2Oy were then systematically examined. Structural characterization demonstrated that the synthesized powder samples show pure phases without any impurity phases. Compared with the Bi2Ca2Co2Oy sample, the resistivity and Seebeck coefficient values of NaF-doped ceramic samples decreased as NaF doping leads to an increase in the carrier concentration of Bi2−xNaxCa2Co2Oy-xFx (x = 0.0, 0.1, 0.2, and 0.3) ceramic samples. The power factor (PF) of the Bi1.8Na0.2Ca2Co2Oy−0.2F0.2 sample shows a maximum value of 71.16 μW m−1K−2 at 823 K. The thermoelectric figure of merit (ZT) of the Bi1.8Na0.2Ca2Co2Oy−0.2F0.2 ceramic samples demonstrates a maximum value of 0.12 at 823 K, which is 1.5 times larger than that of the Bi2Ca2Co2Oy sample.

Keywords

• Bi2Ca2Co2Oy
• Thermoelectric properties
• Double doping
• High-energy ball milling