Challenges in Improving Performance of Oxide Thermoelectrics Using Defect Engineering

Abstract

Oxide thermoelectric materials are considered promising for high-temperature thermoelectric applications in terms of low cost, temperature stability, reversible reaction, and so on. Oxide materials have been intensively studied to suppress the defects and electronic charge carriers for many electronic device applications, but the studies with a high concentration of defects are limited. It desires to improve thermoelectric performance by enhancing its charge transport and lowering its lattice thermal conductivity. For this purpose, here, we modified the stoichiometry of cation and anion vacancies in two different systems to regulate the carrier concentration and explored their thermoelectric properties. Both cation and anion vacancies act as a donor of charge carriers and act as phonon scattering centers, decoupling the electrical conductivity and thermal conductivity.

In-Depth Investigation of the Mechanism of Dehydration-Induced Phase Transformation from Nb3O7(OH) to H-Nb2O5: A Theoretical and Experimental Approach

“…Therefore, it is easy to find that H-Nb 2 O 5 prepared by different raw materials shows different exciton transition processes, which have a great relationship with the transition process. According to the theory of excitons bound to ionized impurities in semiconductors, an exciton can be bound to a singly ionized donor if m e / m h < 0.2. , Indeed, an increase in concentration of oxygen vacancies results in a simultaneous increase of electron effective mass, which has already been confirmed in previous reports. , Then, the value of m e / m h of Nb 3 O 7 (OH)-H is most likely greater than 0.2, indicating that the exciton cannot be stably bound to singly charged point defects. The defects indeed form due to nonstoichiometry in the crystal lattice, which has been confirmed by the preliminary findings .…”

“…6,38 Indeed, an increase in concentration of oxygen vacancies results in a simultaneous increase of electron effective mass, which has already been confirmed in previous reports. 39,40 Then, the value of m e /m h of Nb 3 O 7 (OH)-H is most likely greater than 0.2, indicating that the exciton cannot be stably bound to singly charged point defects. The defects indeed form due to nonstoichiometry in the crystal lattice, which has been confirmed by the preliminary findings.…”