Development of the anodized aluminum substrates for thermoelectric energy converters

Abstract

Operation of the thermoelectric converters requires hot- and cold-side insulating plates with low thermal resistance. In this work, we developed anodized aluminum substrates with physical properties accommodated for thermoelectric converters, which can be a possible alternative to the expensive and brittle commercial ceramics. The XRD, SEM, and EDS analyses were employed to investigate the quality of the prepared samples. The thermal resistance of the developed substrates shows much lower values compared with the commercial ceramics indicating the beneficial effect of the anodized aluminum substrates on the heat transfer through the thermoelectric module. The temperature-dependent breakdown voltage of the Al2O3 anodic layer was estimated as a key parameter that defines the thermoelectric module's workability. For the measurement of the thermal breakdown voltage of dielectric layers, the temperature-controlled testing setup was developed. With the help of the Walther-Fock theory and the measured data, the analytical expression that determines the thickness of the Al2O3 dielectric layer as a function of the anodization voltage and temperature is proposed. Considering Seebeck voltage generated by a thermoelectric module, the desired thickness of the Al2O3 layer can be defined to prevent the destruction of the dielectric substrate during the thermoelectric module operation. The application of the presented results can significantly accelerate the development of mechanically strong, low-cost, and highly efficient thermoelectric energy converters.