Synergistic Enhancement of Electrical Conductivity and Thermoelectric Efficiency in ZnFe 2 O 4 ─Fe 2 O 3 /Graphene Composites

This work demonstrates the successful improvement in the thermoelectric properties of the spinel ZnFe 2 O 4 (ZFO) composite with multilayer graphene. Phase‐pure ZFO prepared using the sol–gel method was mixed with multilayer graphene, compacted, and sintered at 1200 °C for 5 h in an N 2 atmosphere. A significant increment in electrical conductivity from 6.3 S/m of bare ZFO to 1069 S/m at 750 K was achieved for the 7.5 wt% graphene‐incorporated ZnFe 2 O 4 ─Fe 2 O 3 composite. This is because of the weakening of the double Schottky barrier and effective utilization of charge carriers trapped at the grain boundaries. The enhanced thermoelectric performance with a z T of 0.008 at 673 K is obtained for a 5 wt% graphene‐incorporated ZnFe 2 O 4─ Fe 2 O 3 composite due to its low thermal conductivity. The effective reinforcement of graphene with ZFO and also the presence of Fe 2 O 3 as secondary phase make the composite a promising material with improved thermoelectric performance and heat conversion efficiency for high‐temperature thermoelectric applications.