Experimental evaluation of the effect of ceramic plate thermal conductivity on the efficiency of thermoelectric modules

Аuthors

Vorobyov D. V., D. ^*

Moscow Power Engineering Institute (National Research University), 14, Krasnokazarmennaja St., Moscow, 111250, Russia

*e-mail: MakarovPG@mpei.ru

Abstract

This research presents a comprehensive experimental evaluation of the influence exerted by the ther-mophysical properties of ceramic substrates on the overall efficiency and operational stability of thermoelectric modules (TEMs). While the efficiency of TEMs is traditionally viewed through the lens of semiconductor material science and the dimensionless figure of merit (ZT), this study highlights that the total system performance, expressed as the coefficient of performance (COP), is heavily dic-tated by the efficiency of heat transfer through the module’s multilayered assembly. Ceramic plates, which provide essential electrical insulation, simultaneously act as “thermal insulators”, creating para-sitic thermal resistance between the semiconductor junctions and the heat exchange surfaces.
The study utilizes a steady-state coaxial cylinder method to measure the actual thermal conductivity of various ceramic materials, including alumina (Al2O3) with 96 % and 99,7 % purity, and aluminum nit-ride (AlN). Experimental results revealed significant discrepancies between theoretical reference values and real-world performance. Specifically, the measured thermal conductivity of the investigat-ed aluminum nitride was 88,5 W/(m×K), which is approximately twice as low as standard reference values (typically 170 W/(m×K)). This discrepancy is attributed to material porosity and surface de-fects. In contrast, 99,7 % Al2O3 (Polikor) showed a conductivity of 32,3 W/(m×K), aligning well with reference data.
The experimental phase involved testing TEMs with identical geometries but different substrate mate-rials under varying thermal loads and temperature differentials. It was demonstrated that using AlN substrates instead of standard 96 % Al2O3 significantly enhances the COP, particularly in high-heat-flux regimes. For instance, under a heat load of 2,25 W, the AlN-based module achieved a 32 % in-crease in efficiency (improving COP from 0,22 to 0,29). Furthermore, the study found that high ther-mal resistance in Al2O3 substrates leads to increased junction temperatures, causing additional Joule losses and premature thermal degradation. In extreme conditions, such as a 2,5 W load, the Al2O3-based module failed to maintain the required temperature gradient, whereas the AlN module remained stable. These findings confirm that minimizing the thermal resistance of interfaces and performing rigorous quality control of ceramic components are critical for designing high-performance thermoe-lectric systems for precision temperature control.

Keywords:

thermal conductivity, thermal resistance, thermoelectric module, coefficient of performance, TEM

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