Investigation On The Thermoelectric Properties For Ag Doped La₂CuO₄ And Nb Doped SrTiO₃

With the development of human activities and the continuous development of the industrial revolution, some traditional non-renewable energy sources began drying up, resulting in new energy development is urgent. The development and utilization of new energy sources needs to achieve thermoelectric materials. The thermoelectric material has become a hot material science. Thermoelectric（TE） devices can convert waste heat originating from various sources, for example, electric power plants, factories, automobiles, computers and even human bodies. Applications of thermoelectric materials are mainly thermoelectric power generation and thermoelectric cooling. Thermoelectric power generation using the Seebeck effect, from heat energy directly into electrical energy. Thermoelectric cooling can be manufactured thermoelectric refrigeration utilizing Peltier effect. Thermoelectric cooling has several advantages: small size, light weight, no mechanical transmission parts, working no noise and no cooling liquid, thus there is no problem of environment pollution. It can achieve precise temperature control, fast response and long life components. Therefore, thermoelectric cooling has been used in many areas. Became the highlight of the 21 century green thermoelectric materials research.However, the greatest challenge that the thermoelectric material facing is the energy conversion efficient is not enough. To achieve the goals of large-scale applications of thermoelectric materials, some researchers have tried to improve the performance of the exist material by means of doping. At present, some doping techniques are generally complex or high requirements for equipment, it’s difficult to mass production. Ion beam implantation doping process has been successfully applied to the oxide film material. Ion beam implantation is make the injected elements ionized into plasma, then get relatively pure ion by the analysis of the magnetic analyzer and the speed of the accelerator, and into the solid target at a faster rate, in order to change the physical and chemical properties of the solid surfaces.We study the thermal transport properties of p-type oxide thermoelectric material Ag-doped La2 Cu O4, and researched the effect of thermoelectric properties of ion beam implantation of Nb doped n-type Sr TiO₃.The concrete works of this paper is as follows:1、A series of Ag addition La₂CuO₄ polycrystalline ceramics have synthesized by traditional solid state reaction method, and thermoelectric properties are investigated. Resistivity and Seebeck coefficient of these samples decrease with the increase of Ag dose. With the increase of Ag content, the thermal conductivity first decreases and then increases. Thermoelectric Figure of Merit ZT（ZT=S2T/ρκ） is computed by the experimental dates of resistivity, Seebeck coefficient, thermal conductivity and absolute temperature.Maximum ZT of each sample appear at around 300 K and it shift to lower temperature with the increase of Ag dose. At 308 K, 5% Ag addition sample show the maximum ZT in this series of Ag addition La2 Cu O4 polycrystalline ceramics. It is 0.018 and larger than double of pure La2 Cu O4（0.0077 @ 314 K）.2、The stoichiometric ratio of SrCO₃（99.95%）, TiO₂（99.99%） and Nb₂O₅（99.99%）, using traditional solid state reaction method preparation of Nb-doped Sr TiO₃ powder. The doping dose of Nb element is 1%、2%、5%、10%、20%, respectively. Using XRD to analyze the phase of the series, and then the series of powders were determined to be a pure single phase material. Using PPMS measured the resistivity and Seebeck coefficient of the series of bulk samples in the temperature range 15-380 K. The results demonstrated that with the elements Nb-doped can effectively change the bulk power factor. When the doping component was 2%, the ZT approached a maximum value of 0.033 at 380 K.3、High quality c-axis oriented Sr TiO₃ thin film have been epitaxial grown on（001） La Al O3 single crystal substrates using the Pulsed Laser Deposition（PLD）, a series of film were grown under 5 Pa oxygen atmosphere. And different doses of Nb ions were implanted into the Sr TiO₃ thin film lattice using an ion beam injection technique. The resistivity and Seebeck coefficient of the series of films samples were measured in the temperature range 50-380 K. The results demonstrated that the STO-Nb100 having the highest power factor at room temperature and the highest measured temperature 380 K, were 0.34 m W/m·K2 and 0.44 m W/m·K2, respectively,. It was 10 times as much as that of the undoped Sr TiO₃ thin film.