Fabrication And Characterization Of P-Type BiSbTe Based Thermo-Electro-Magnetic Films

With the development of microelectronic integration technology,the heat generation of processor increases,and an effective thermal management scheme is urgently needed.Thermoelectric thin film enables the integration of thermoelectric power generation and refrigeration into microelectronic systems.Thin-film devices display more efficient refrigeration capacity and faster response in smaller spaces.However,compared with bulk materials,thermoelectric thin films always have a low performance,which greatly limits their practical application.Therefore,the preparation of thermoelectric thin films with high thermoelectric properties is of great significance in promoting the development of micro-electronic market.Some recent studies have shown that introducing magnetic materials into thermoelectric materials can effectively improve the thermoelectric properties of bulk thermoelectric materials by introducing new thermo-electro-magnetic coupling effects,whereas the application of such coupling effects in thermoelectric thin films remains unclear.Therefore,in this paper,Bi_0.5Sb_1.5Te₃/epoxy composite thermoelectric film was prepared,and the influence on the electrical transport,refrigeration performance and magnetic properties of thermoelectric film materials was studied by introducing magnetic elements with disordered and ordered distribution.The main research contents are as follows:（1）A series of xCo/Bi_0.5Sb_1.5Te₃composite thermoelectric thin films were prepared by ball milling,screen printing and hot pressing.Co shows a disordered distribution in the thermoelectric thin films.The in-situ reaction of Co nanoparticles with Te on Bi_0.5Sb_1.5Te₃lattice resulted in the formation of Co Te₂and Bi _Te’antiposition defects,which significantly increased the carrier concentration and improved the conductivity of the films.The conductivity and power factor of 0.2wt%Co/Bi_0.5Sb_1.5Te₃composite thermo-electro-magnetic thin films reach the maximum values of 5.11×10⁴S·m^-1and 2.28 m W·m^-1·K^-2at 300 K,which are 40%and 34.1%higher than that of matrix thin films.Using the refrigeration performance test platform built by our research group,a maximum cooling temperature difference of0.5 K was achieved on the 0.2wt%Co/Bi_0.5Sb_1.5Te₃composite thermo-electro-magnetic film at an applied working current of 40 m A,which is 2.5times that of the matrix film.（2）The ordered magnetic unit in Bi_0.5Sb_1.5Te₃/epoxy composite thermoelectric films was constructed by femtosecond laser induced transfer.Fe,Co and Ni magnetic elements deposited on glass substrates were successfully transferred to the surface of thin films by femtosecond laser and the macroscopic magnetic ordering was formed.Fe/Bi_0.5Sb_1.5Te₃magnetic ordered thermoelectric thin films were prepared by femtosecond laser induced transfer at different output powers.It was found that with the increase of output power,the area of unit magnetic element gradually enlarged,and the ferromagnetism of the thin films gradually increased.The power factor of the film transferred by femtosecond laser with the output power of 40%（0.6 W）,200KHz frequency,wavelength of 1030 nm,3μJ energy is more than 10%higher than that of the film not transferred,and the extra magnetic scattering maintains a high Seebeck coefficient of the films.（3）A stacking sequence of magnetic materials was constructed in Bi_0.5Sb_1.5Te₃/epoxy composite thermoelectric film by means of mask plate combined with vacuum evaporation.This method can realize a magnetic ordering in micron level,and the shape and spacing of such ordering can be precisely controlled.The maximum power factor of the layered magnetic ordered thin films prepared with a d=150μm spacing mask is 1.19 m W·m^-1·K^-2,which is 16%higher than that of the matrix counterpart.At an applied working current of 20 m A,the cold end cooling temperature difference of the single-arm prototype device prepared by the sandwich magnetic ordered film with d=150μm pitch mask is doubled than that of the single-arm prototype device prepared by the matrix film without magnetic ordering.