Isovalent Doping of Cu2+ Induced Elastic Strain on Cobalt Spinel Oxides for Enhancing Room Temperature Thermoelectric Application

Abstract

A novel thermoelectric material, CuxCo1-xAl2O4 (x=0.02-0.10) was developed using a microwave combustion method with urea as the fuel source and investigated for the room temperature thermoelectric applications. The spinel phase was analyzed using XRD, and the spinel Co-O-Al bond were identified at the band region of 779cm-1 in the FT-IR spectrum. SEM revealed a marigold flower like pattern in the morphology, while TEM showed a cubic morphology, and elemental composition are confirmed by EDAX. Additionally, optical characteristics of the pristine and Cu doped samples were thoroughly analyzed by UV- DRS spectroscopy. EPR measurement confirmed the presence of free electrons which are crucial for electrical conductivity. XPS analysis further verified the oxidation states of each element. To investigate the thermoelectric properties of CoAl2O4 and CuxCo1-xAl2O4 (x=0.02-0.10), hall measurements were conducted, revealing the highest carrier concentration was found as 8.728×1016cm-3 for Pristine CoAl2O4. Notably, the highest electrical conductivity was found as 2.48×10-2 Scm-1, while the lowest thermal conductivity measured was 0.0522W/mK for Cu0.10Co0.90Al2O4. The Seebeck co-efficient for the pristine sample was 730 μV/K, which decreased to 427 μV/K for Cu0.10Co0.90Al2O4. The highest power factor observed was 5.1 nWcm-1K-2 for Cu0.10Co0.90Al2O4. This study presents the obtained results and the fabrication of a wearable device using p-type (CoAl2O4) and n-type (Cu0.10Co0.90Al2O4) materials, achieving an output of 3.6mV with a temperature difference of 1.5K”.