Effect of Poly(Vinyl Alcohol) on thermoelectric properties of sodium cobalt oxide

Organic polymer composites are relatively simple to process and are therefore used in thermoelectric materials. The organic polymers are used as an adhesive agent between thermoelectric material grains. Thermoelectric effects of poly(vinyl alcohol) (PVA) composited with sodium cobalt oxide (NaxCoO2) were studied in this work. PVA is a low cost and an excellent biocompatibility polymer. High electrical conductivity, high Seebeck coefficient and low thermal conductivity are required in thermoelectric materials. As PVA is an insulating material, the PVA in between NaxCoO2 grain boundaries has an effect on the low electrical conductivity of NaxCoO2 composite. This results in a decrease in thermoelectric efficiency. However, PVA has been utilized to increase the Seebeck coefficient and also enhance thermoelectric efficiency. In order to improve the electrical conductivity of NaxCoO2 composite, released PVA was produced by furnace heating at 500 °C to eliminate PVA from NaxCoO2/PVA sample. The general thermoelectric parameters including the Seebeck coefficient, electrical conductivity and power factor of NaxCoO2/PVA and composite and PVA removal sample were compared. X-ray diffraction patterns (XRD) and scanning electron microscope (SEM) images were used to identify the phase identification and morphology study, respectively. The results showed that the PVA removal sample had higher electrical conductivity than the NaxCoO2/PVA sample. However, NaxCoO2/PVA sample had higher thermoelectric performance than the PVA removal sample because the NaxCoO2/PVA sample showed higher Seebeck coefficient and power factor.