| is a basic material with a wide perspective of SOFC cathode materials with moderate temperature. It shows a unique electronic phase change with the change of temperature. It is a nonmagnetic insulator at low temperature, changes to semiconductor at medium temperature and to conductor with the raise of temperature. In general, there are some certain methods as follows of synthesis of cathode materials: Hydrogenation, Sol-gel, Solidification, electrochemical synthesis, Co-precipitation, Calcinations, Combustion, and Vaporized Plating. However, all of them are done at normal pressure and have certain disadvantages, it is very necessary to develop a new method of synthesis. High-pressure-and-temperature method embodies some unique advantages----high-speed reaction, efficient transformation, low temperature for synthesis and fairly short time. Besides, this method can produce single-phase material. Therefore, this method is very significant in the research and development of SOFC cathode materials, by which SOFC cathode materials with perovskite structure, when we synthesize the SmCoO3 and study the relationship between the structure and performance of it.This article deals with the effect of pressure and temperature that have on perovskite structure by means of SmCoO3, the cathode material with the structure of perovskite-type compound, which is synthesized by using the high- pressure -and- temperature method. It defines the optimum pressure and temperature for single-phase SmCoO3 synthesis. And it's also concerned with the performance of the optimum synthesis, by way of XRD, high-temperature conductance Ramanspectrum and heat analysis. It turns out to be: Under the same temperature, if pressure changes, or vice versa, samples' synthesis is greatly affected. By studying SmCoO3's synthesis we find that where the intensity of pressure reaches 3.90Gpa and the temperature approaches to 882癈, the perovskite structure begins to form, and becomes complete at the temperature of 1061癈. However, if the temperature goes beyond 1061癈, complex-phase is produced. Changing the pressure and temperature ,it is hard to synthesize single phase of SmCoO}, So when the intensity of pressure reaches 3.90Gpa and the temperature 1061癈, its sample is nearly single-phase and fairly complete shown by XRD spectrum.The test of property of the synthetic compounds in different temperature shows the truth that the conductivity in high temperature and Raman chart of the samples show superiority, in the condition of 3.90Gpa . 106TC, to those in other conditions. The Raman of the about kind of samples is more complete than others, which explains the best compounding temperature is 1061癈 for the material of SmCoO3 under 3.90Gpa.In order to compare the influences brought by different compounding methods to the crystallization of material of SmCoO3, we took two other methods of solidification reaction and ball milling method to synthesize the sample of SmCoO3. We got the complete conditions for photocopy through XRD charter respectively, the best for high temperature: 1080癈, 1200癈; The best for ball milling: 100h-180h(300R/mm).It is discovered from the comparison of conductivity in high temperature among the synthetics in different conditions, that their conducting rates are very different. At the same temperature, the sample synthesized by solidification has the highest conductivity, the one by high pressure has a smaller one and that oneby ball milling has the smallest one. This explains the electric properties of samples synthesized under- different methods, has changed, this is because that the substructure of sample has changed under different methods.It is discovered from the comparison of thermal expansion among the products in different conditions, that the sample synthesized by high pressure has the same high pressure with the one synthesized by ball milling, but the one synthesized by solidification has a highest one. However, all of their thermal expansion are bigger than the one of SDC (Ceo.85Smo0.15Oa) and not are acc...
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