Study On Bismuth Telluride-based Thermoelectric Devices

With the rapid development in electronics technology,internal thermal management gradually becomes an important problem for devices with integrated circuits.Thermoelectric(TE)devices are expected to be a potential candidate to solve the thermal management problem due to its good cooling performance.However,there are problems to be solved for the most used Bi2Te3-based TE devices.The mechanical and TE properties of Bi2Te3-based materials produced by zone melting technique are very low,making it difficult to process TE elements.Although mechanical performance can be improved through preparing the polycrystalline Bi2Te3-based materials,the intrinsic donor-like effect can degrade the TE performance near room temperature.Therefore,suppressing the donor-like effect becomes significant.In the aspect of TE devices,traditional TE devices have been applied in many devices such as car air-condition and semiconductor fridge.Micro TE devices are expected to be employed in the field of heat dissipation in chip and LED devices.Although there are techniques reported to produce the micro devices,it is difficult to realize mass-production in reality due to the complicated procedures and high cost.Therefore,it is necessary to study practicable techniques for the micro TE devices.Weak donor-like effect can improve the TE performance of both N-type Bi2Te2.79Se0.21 and P-type Bi0.3Sb1.7Te3 materials.Basal deformation and cyclical pressing can be introduced to obtain the weak donor-like effect.For the N-type Bi2Te2.79Se0.21,This effect helps keep the PF at high level and obtain low thermal conductivity of 1.18 W·m-1·K-1,which enhanced the figure of merit(ZT)from 0.78 to 1.0.For the P-type Bi0.3Sb1.7Te3,similar phenomenon was observed as weak donor-like effect was introduced by multiple deformation.Little change was observed in the PFs of Bi0.3Sb1.7Te3.The thermal conductivity decreased from 1.75 W·m-1·K-1 to 1.48 W·m-1·K-1,which improved the ZT from 0.9 to 1.1.Although the concentration of anti-site defects has little influence on the donor-like effect,the lattice thermal conductivity can be affected by the change of anti-site defects.The configuration of micro TE device is the same as the traditional one.The technique for processing micro devices can be developed based on the procedures of traditional TE devices.Therefore,the traditional TE device was firstly obtained through solving the thermal stress problem.Based on that,researches on the micro TE device were conducted.The main procedures of elements processing and electric plating were improved.Steel module with square holes were designed to fixing micro TE element.Two-step sintering technique was employed to obtain the micro device.