Editing Precision Thermocouple Based Temperature Measurement System (section)

=== 2.3. Material Selection ===
Zinc oxide (ZnO) is recognised as an n-type semiconductor and exhibits a pronounced Seebeck effect. When a temperature gradient is established across the material, charge carriers migrate from the hotter side to the cooler side, resulting in the generation of a thermoelectric voltage. The magnitude and polarity of this voltage depend on the properties of the material, with ZnO typically exhibiting a negative Seebeck coefficient due to the predominant conduction of electrons. The Seebeck coefficient for zinc oxide (ZnO) usually falls within the range of approximately –100 to –500 µV/K, which can vary based on factors such as temperature, doping, and the methods used in material preparation. The negative value indicates that ZnO functions as an n-type semiconductor, with electrons serving as the dominant charge carriers.

The ZnO was prepared by grinding 3 grams of Sigma-Aldrich 99% pure ZnO and making a circular pellet under mechanical pressure. The pellet was first annealed for 5 hours at 300&deg;C. Since the pellet was not hard enough to cut, it was re-annealed at 500&deg;C for 3 hours. On cooling, it was cut into a rectangular shape of thickness 3 mm.