La < Sub > 1 - X < / Sub > Sr < Sub > X < / Sub > Coo < Sub > 3 < / Sub > Ceramic, Membrane Preparation And Membrane Of Lateral Thermoelectric Effect Research

Recently, perovskite structure La1-xSrxCoO3have attracted increasing attention as their large potential technologial applications. The mixed electronic/oxide-ionic conductivity in thses compounds enables them to be good electrode materials for solid oxide fuel cells, outstanding membrane materials for oxygen separation and gas sensor. Low Sr doping La1-xSrxCoO3with high Seebeck coefficient and large thermoelectric Figure of Merit, also render them as promising thermoelectric materials for energy conversion. Apart from these technological applications, La1-xSrxCoO3also present other interesting physical properties, such as the negative magnetoresistance effect, the transition of the spin state of Co ion excited by thermal and phase separation. This paper focuses on the prepartion of La1-xSrxCoO3ceramics and thin films, as well as the transverse thermoelectric effect in thin films. Sr content to the influence of crystal structure and microstructure of La1-xSrxCoO3ceramics, the epitaxial characterizations of thin films on vicinal cut substrates and the modification of response rate of transverse thermoelectric voltage by resistivity have been mainly investigated.Pure phase La1-xSrxCoO3(0≤x≤1) ceramics have been prepared by a solid-state reaction method in air with the sintering condition of910℃/20h+1100℃/10h. X-ray diffraction results indicate that with increasing Sr content, the crystal structure of La1-xSrxCoO3ceramics turns into cubic phase from rhombohedral phase in the range of x=0.3～0.4, and the lattice parameters continually increase. Second-sintering in air makes the phase structure of high Sr doping ceramics change to cubic phase from hexagonal phase. The electrical transport properties of La1-xSrxCoO3(0≤x≤1) ceramics in the temperature range of80K-300K have been measured in air by four-probe method, which shows that La1-xSrxCoO3ceramics exhibit semiconducting transport behavior for0≤x≤0.2and0.9≤x≤1.0. While metallic transport behavior has been observed in La1-xSrxCoO3(0.3≤x≤0.8). The room temperature resistivity continuously decreases with increasing Sr content x for0≤x≤0.7and there exists the unusual enlargement of resistivity in0.8≤x≤1. Microstructure analysis by SEM shows that both the grain size and the pore size enlarge, and the number of grain boundaries becomes small with increasing Sr content. The phenomenological kinetic grain growth theory has been used to interpret the change of porous microstructure with different Sr content and the change of apparent activation energy Q and kinetic grain growth n in La1-xSrxCoO3with increasing Sr content is thought to be responsible for the markedly variable microstructure.Pulse laser deposition technology has been employed to grow La1-xSrxCoO3(0.05≤x≤0.5) thin films on planar and vicinal cut single crystal substrates. Microstructure and electrical properties of thin films on planar substrates demonstrate that LAO(100) substrate is much more suitable for La1-xSrxCoO3film growth than STO(100) and large oxygen pressure in the deposition process can obviously reduces the resistance of thin film. X-ray diffraction technology has been used to characterize the epitaxial quality of tilted thin films and the results show that with increasing tilted angle (corresponding to small terrace width), the crystalline and epitaxial qualities of tilted thin films become poor.Pulse laser has been used as the thermal source to heat the top surface of thin films in order to study the transverse thermoelectric effect in tilted La1-xSrxCoO3(0.05≤x≤0.5) thin films. With the increase of Sr content x, the peak voltage of transverse thermoelectric voltage signal first increases and then decreases. At x=0.3, there is a maximum voltage response, corresponding to the largest transverse thermoelectric Figure of Merit. Resistivity is the main physical parameter to determine the transverse thermoelectric response time. Both the experiment research and the theoretical calculation have confirmed that low resistivity results in small optical penetration depth and then induces fast response rate.