Fabrication And Cooling Performances Of Bi_0.5Sb_1.5Te₃/Epoxy Flexible Thermoelectric Devices

With the development of microelectronics integration technology,the electronic devices tend to be miniaturized.At the same time,due to excessive heat generation of the devices,there is an urgent need to develop efficient thermal management solutions.The thermal management technology based on Peltier effect of thick flim thermoelectric?TE?materials has attracted increasing attention due to the unique advantages such as good compactness,lightweight and low cost.At present,the biggest problem of Bi₂Te₃ based thick film cooling devices is that the conductivity of thick film is low,and the internal resistance of devices is large,resulting in no obvious cooling effect.We have developed a new process by the combination of brush-printing and hot-pressing processes for the preparation of Bi_0.5Sb_1.5Te₃/epoxy composite thick film with?000l?preferential orientation and excellent electrical transport properties.The experimental tests were performed to evaluate the cooling performance of the devices.A series of Bi0.5Sb1.5Te3/epoxy composite thick films with thickness of 100-150?m were prepared by brush-printing and hot-pressing processes.The effects of curing temperature,curing time and hot pressure on phase composition,microstructure,and TE properties of the thick films were studied.The experimental results show that the thick films prepared at curing temperature in the range of473⁶23 K at 10 h were composed of single-phase Bi_0.5Sb_1.5Te₃.The Bi_0.5Sb_1.5Te₃particles have no obvious orientation when the curing temperature was 423 K.The curing temperature increases led to significant enhancements in the?000l?preferential orientation and densification,and remarkable decrease in surface roughness and defects.Benefiting from these evolutions in preferential orientations,Bi_0.5Sb_1.5Te₃/epoxy thick films exhibited remarkably improved electrical conductivity,Seebeck and power factor.Therfore,the optimum curing temperature was 623 K.The thick film cured at 8¹4 h and 623 K consisted of single-phase Bi_0.5Sb_1.5Te₃.The density of 8¹0 h cured thick film gradually increases but decrease cured over 10 h,due to decomposition of the epoxy resin system let the increases of voids and cracks.The electrical transport performance of thick film increases first and then decreases with the increase of curing time.Therfore,the optimum curing time was 10 h.The hot pressure causes the random Bi0.5Sb1.5Te3 particles to be rearranged along the?000l?orientation,and the preferential orientation of the Bi_0.5Sb_1.5Te₃particles on the?000l?plane increases significantly with the increase of hot pressure under 623 K,10 h,0⁴MPa.The Bi_0.5Sb_1.5Te₃ particles were arranged along the?000l?plane,which reduces the defects and improves the density of the thick film.Hot-pressing curing significantly increased the electrical transport performance of the thick film.The highest power factor of the Bi_0.5Sb_1.5Te₃/epoxy thick films reached 0.84 mW·m^-1·K^-2 at 300 K,increased by 250%as compared with that of our non-pressure thick film.A prototype flexible thick film device had been designed and successfully fabricated,which consists of Bi_0.5Sb_1.5Te₃/epoxy thick films with the?000l?preferential orientation and Al/Cu/Ni multilayer thin film electrodes.A device for measuring the cooling capacity of the device was set up,and the temperature difference between the cold side and the hot side of the device was tested under different DC currents.Under an applied current of 0.06 A,the maximum stable cooling temperature difference??T?reached 6.2 K,increased by about 24%as compared with the highest temperature difference of 5 K reported by other groups.