Experimental Investigation of Zinc Antimonide Thin Films under Different Thermal Boundary Conditions

Zinc antimonide compound ZnxSby is one of the most efficient thermoelectric (TE) materials known at high temperatures regarding to its exceptional low thermal conductivity. For this reason, it continues to be the focus of active research. However, before practical use in actual conditions, it is imperative to analyze the thermo electrical behavior of these materials.
In this study, the results are considered for different hot side temperature of the film in steady state condition. Six temperatures at hot side of the specimen are provided; 150, 200, 250, 300, 350, and 400 ᵒC. At the beginning of each test, the specimen needed a few minutes for getting stationary state. But this time is different for each temperature of hot side. Results showed that in higher temperature differences between hot and cold side (ΔT), the voltage will be higher. In steady state, the voltage will be almost constant but different for each hot side temperature. The voltage decreased by remaining in higher constant temperature of hot side, while this reduction will be slight or even negligible for lower hot side temperatures. The results show that, in different hot side temperatures, trends of the voltage versus ΔT is linear for all cases, showing that the electrical potential difference is increasing by temperature for all cases with the same slope. Also the value of Seebeck coefficient (α) is almost constant for all cases. The obtained value of α can compete with developed bulk TEG materials in literature. The thin film is able to operate in relatively high range of temperature with long working period without failure.
Furthermore, effects of implementing thermal cycling on stability analysis of a TEG sample are considered. By testing the thermoelectric thin film specimen during a thermal cycling, behavior of the TEG sample in similar working conditions can be predicted if results in severe degradation of thermoelectric sample. In this stage, the temperature of hot side varies by a cyclic distribution up to the film’s critical temperature by using an on/off switch. Cold side is kept close to the room temperature.