Preparation Of Bi₂Te₃-based Thermoelectric Films And Thermoelectric Generator

As one of the best thermoelectric materials near room temperature, Bi2Te3 is widely applied in thermoelectric cooling and thermoelectric generation. Their thick or thin film device can be used for cooling and thermoelectric generation in some irregular or narrow space. In this thesis, some work are carried out for Bi2Te3 thermoelectric films and their flexible thermoelectric devices with the method of tape casting and thermal evaporation.In this thesis, tape casting is successfully utilized for preparing the P-type Bi0.48Sb1.52Te3 thermoelectric thick films. The effects of the binder concentration and the annealing temperature on the performance of the thermoelectric films are investigated in detail. It is found that the binder concentration has an effect on the molding quality while the annealing temperature makes great difference on the thermoelectric performance of the thick films. As a result, it is definited that the best binder concentration is 50mg/ml, and the annealing temperature is 500?. Correspondingly, the best thermoelectric films has the Seebeck coefficient of 239?V/K and the power factor of 1.32×10-6W/mK2.Thermal evaporation is used to prepare P-type Bi0.48Sb1.52Te3 thermoelectric films and N-type Bi2Se0.3Te2.7 thermoelectric films. For P-type thermoelectric films, the maximum value of the Seebeck coefficient is 35?V/K, while the conductivity is 0.78×105S/m and the power factor is 0.97×10-4W/mK2. On the other hand, for N-type thermoelectric films, the maximum value of the power factor is 3.8×10-4W/mK2 when the evaporation current is 90 A and the base temperature is 100?.With the method of thermal evaporation mentioned before, flexible thermoelectric device is made from P-type and N-type thermoelectric films. The open-circuit voltage from the fabricated device is 48.9mV while the temperature difference is 100 K. After a load resistance of 29K? is connected, the max output power of 18.24×10-9W is obtained.As analyzed in the thesis, there are still a lot of improvement space for the fabrication process, and much conditions can be further optimized to get better films. At the end of this thesis, the full content is summarized, and some suggestions are put forward for further experiments.