Study On Rera-earth Aluminum Materials Using In Novel Thermal Barriers Coatings

To improve the thermal efficiency of high-temperature gas turbine,research on preparing rare-earth aluminate materials in addition to YSZ using in novel thermal barrier coatings has not only important scientific significance but also applications.RAlO₃ rare-earth aluminate materials have been synthesized using rare-earth oxide powder R₂O₃(R=Y,La,Pr,Nd,Sm,Eu,Gd) and Al₂O₃ powders at 1450℃～1650℃. Synthesis temperature choosen at 1550℃×6h is better.Thermal conductivities at room temperature is between 4.06 to 6.46 W·m^-1K^-1.R₃Al₅O₁₂ rare-earth aluminate materials have been synthesized using rare-earth oxide powder R₂O₃(R=Y,Tb,Dy,Ho,Er,Tm,Yb) and Al₂O₃ powders at 1550℃～1700℃. Pure garnet phase materials can be obtained at 1700℃×6h.Thermal conductivities of R₃Al₅O₁₂ rare-earth aluminate materials temperature at room are between 3.74 to 5.78W·m^-1K^-1,lower than perovskite-type rare-earth aluminate phase materials.Low thermal expansion coefficient of Tb₃Al₅O₁₂ and Tm₃Al₅O₁₂ are mainly due to the lattice expansion by massive atomic and molar heat capacity.Rare-earth co-doped Tm_xTb_3-xAl₅O₁₂ aluminate materials are prepared using Tm₂O₃, Tb₂O₃ and Al₂O₃ oxide powder at 1700℃×2h.Tb₃Al₅O₁₂ and Tm₃Al₅O₁₂ can become a continuous solid solution.The thermal conductivities at room temperature are about 3.67～4.52W·m^-1·K^-1.Slightly doped by rare-earth ions can cause a significant reduction of thermal conductivity,but the lower level is nonlinear with the doping concentration.Thermal conductivity theory model of doped garnet structure materials has been established by theoretical analysis and calculations.Three reasons lead to lower the thermal conductivity of garnet materials:the contribution of mass fluctuation M_Tm/M_Tb;the contribution of the differences of lattice coupling force G_Tm/G_Tb;the contribution of lattice strain field fluctuations and the coordination polyhedron space fluctuationsδ_Tm/δ_Tb.The study lays an important experimental and theoretical basis on application of rare-earth aluminate materials in TBCs.