Influence Of The Equimolar Substitution Of Gd₂ O₃ For Y₂O₃ On The Structure And Properties Of Y₂O₃ -Ta₂O₅-ZrO₂ Ceramics

The ceramic coating of thermal barrier coatings was used to protect the metal base, which have a broad and significant pplication in the aviation, aerospace, automotive ,large-scale thermal power generation and other aspects.This not only can improve corrosion resistance, but also improve gas turbine efficiency and the working temperature of engine hot components.The widely used 6⁸wt% Y₂O₃ partially stabilized ZrO₂(6⁸YSZ) thermal barrier coatings have many good characteristics, but it is more likely to occur t-m phase transformation in the 1443K. So (6⁸)YSZ have to work below the temperature of 1443K. It has been not meeting the needs of future development. Therefore, it is important for thermal barrier coating to develop novel ceramics material to alternative YSZ. In recent years ,the Ta₂O₅-Y₂O₃-ZrO₂ ceramic materials of thermal barrier coatings is relatively superior to other new type materials. The Ta₂O₅-Y₂O₃-ZrO₂ material solely composed with tetragonal phase. The microstructure is homogeneous than that of YSZ. The thermal expansion coefficient is higher than YSZ.The thermal conductivity is lower than YSZ. When the temperature is above 1500℃, the Ta₂O₅-Y₂O₃-ZrO₂ material is also stable in the tetragonal phase. The Ta₂O₅-Y₂O₃-ZrO₂ coating has light cirrosion when thermal cycled 500h at 1100℃.But the YSZ coating is shed when thermal cycled 50-100h at 1100℃.This text take Ta₂O₅,Gd₂O₃,Y₂O₃,ZrO₂ for rawmaterial ,on the basis of Ta₂O₅-Y₂O₃-ZrO₂ use Gd3+substitute for Y3+ until Y3+ was fully displaced by Gd3+.Gd₂O₃ doped Ta₂O₅-Y₂O₃-ZrO₂ ceramics and Ta₂O₅-Y₂O₃-ZrO₂ ceramics were prepared using the solid state reaction method. The phase structure, microstructure ,thermal expansion and thermal conductivity behavior of the ceramics were characterized by X-ray diffraction, scanning electron microscopy, dilatometer and laset thermal diffusivity respectively. The results showed that the Gd₂O₃-Y₂O₃-Ta₂O₅-ZrO₂ceramics material and Ta₂O₅-Y₂O₃-ZrO₂ ceramics material are composed mainly of the tetragonal phase. When the content of Gd3+substitute for Y3+ is increased, the content of the monoclinic phase and bulk density basically increase, whereas the grain size relatively homogeneous and the thermal expansion coefficient decrease. When the content of Gd3+substitute for Y3+ is 2mol%,3mol%,4mol%,6mol%,7mol%, The thermal conductivity of the Gd₂O₃-Y₂O₃-Ta₂O₅-ZrO₂ ceramics material is lower than that of Ta₂O₅-Y₂O₃-ZrO₂ ceramics material. It has the smallest thermal conductivity when the content of Gd3+ substitute for Y3+ is 2mol%. This is propitious to improve the service life of thermal barrier coatings.