Study On The Thermophysical Properties Of R⁴⁺/R⁵⁺ Ion-doped SmNb/TaO₄

With the continuous development of gas turbines toward high temperature and high efficiency,the working environment in the combustion system becomes more severe and severe.Many metal parts will undergo more severe heat,thermal shock,hot corrosion and particle erosion.Therefore,ceramic thermal barrier coating materials are required to provide better thermal protection for the alloy blades.Thermal barrier coating materials require lower thermal conductivity and a stable chemical structure.The main research idea of this dissertation is that SmTa/NbO₄ ceramic materials are doped with different ions to obtain a thermal barrier coating material with lower thermal conductivity and more stable chemical properties,and potential applications for high temperature thermal gas turbines are studied.The new thermal barrier coating material.The specific contents are as follows:Through analysis of XRD and Raman,it was found that doping ions did not change the crystal structure of SmTaO₄ ceramics,and its phase structure was still a single monoclinic phase.Combined with the SEM image,it was found that the size of the particles was1 to 10?m,the size was uniform,and pores did not appear,which helped to improve the compactness of the material and maintain the stability of the material.At the same time,by analyzing the Raman and XRD of SmNb_1-XTa_XO₄,it is found that there are two different phases when the content of doped Ta₂O₅ is less than0.2%and higher than 0.4%.Obvious iron spheres can be observed from the SEM image.The SmTaO₄ doped with Zr⁴⁺,Ti⁴⁺,and Ce⁴⁺tetravalent ions with small difference in radius and relative atomic mass difference is selected.When the temperature is 800?,the thermal conductivity of the SmTaO₄ ceramic material doped with 2%mol of ZrO₂ can be achieved.1.2W/m.K,Sm TaO₄ ceramic material doped with 2%mol of CeO₂ has a thermal conductivity as low as 0.9W/m.K,except for the poor Ti⁴⁺doping effect,doping with CeO₂ in SmTaO₄ ceramic material.ZrO₂ can reduce its thermal conductivity to a large extent.After doping 4%Ta₂O₅ in SmNbO₄,the thermal expansion coefficient of SmNb_1-XTa_XO₄ can reach 12.2×10^-66 K^-11 at 1200°C,close to the Ni-Cr alloy.Doping Ta₂O₅ can greatly improve its thermal expansion performance.Studies have found that undoped SmNbO₄ ceramics have good optical properties.In the 4f electron orbital layer filled with Sm position,the internal 4f⁵ electron transition in the Sm shell will reduce the reflectivity of the SmNb_1-XTa_XO₄ ceramic with a bandgap width of 4.3 to5.0 ev.The addition of Ta in Sm NbO₄ can effectively reduce the thermal conductivity.By testing its thermal conductivity,it was found that the thermal conductivity of Ta₂O₅ doped with 0%at 900°C is the lowest,and the lowest value is 1.33 W.m^-1.K^-1.From this we believe that SmNb_1-XTa_XO₄ ceramics are promising as a new TBC material due to their unique iron elasticity and outstanding thermal properties.