稀土钽酸盐(RETaO_(4))高熵陶瓷的制备与热学性能研究

Preparation and Thermal Properties of Rare Earth Tantalates(RETaO4)High-entropy Ceramics

采用固相法制备了三种具有单斜结构的单相固溶体稀土钽酸盐高熵陶瓷(Nd_(1/6)Sm_(1/6)Eu_(1/6)Gd_(1/6)Dy1/6Ho_(1/6))TaO_(4)(6RETaO_(4))、(Nd_(1/5)Sm_(1/5)Eu_(1/5)Gd_(1/5)Dy_(1/5))TaO_(4)(5RETaO_(4))和(Nd1/4Sm1/4Eu1/4Gd1/4)TaO_(4)(4RETaO_(4)),扫描透射电子显微镜-X射线能谱(STEM-EDS)的分析表明掺杂的稀土元素分布均匀。通过扫描电子显微镜(SEM)观察到由四方-单斜的二级铁弹相变形成的铁弹畴。热膨胀测试表明RETaO_(4)高熵陶瓷在1200℃以下具有良好的热稳定性,其中6RETaO_(4)的热膨胀系数可以达到9.25×10^(-6)K^(-1)(1200℃)。由于高熵效应带来的声子散射增加,RETaO_(4)高熵陶瓷具有较低的晶格热导率(2.98~1.23 W·m^(-1)·K^(-1),100~1000℃),并且表现出良好的力学性能(6RETaO_(4),(9.97±2.2)GPa),是潜在的下一代热障涂层材料。

Single-phase solid solution monoclinic structure high-entropy tantalates(Nd_(1/6)Sm_(1/6)Eu_(1/6)Gd_(1/6)Dy1/6Ho_(1/6))TaO_(4)(6RETaO_(4)),(Nd_(1/5)Sm_(1/5)Eu_(1/5)Gd_(1/5)Dy_(1/5))TaO_(4)(5RETaO_(4)),(Nd1/4Sm1/4Eu1/4Gd1/4)TaO_(4)(4RETaO_(4))were prepared by solid state method.STEM-EDS result shows the rare earth elements are uniformly distributed without segregation.The ferroelastic domain observed through SEM derived from the second ferroelastic phase transition.The thermal expansion experiment suggests the good thermal stability below 1200℃,where the thermal expansion coefficient of 6RETaO_(4)reaches 9.25×10^(-6)K^(-1)at 1200℃.Due to the increase of phonon scattering derived from high-entropy effect,RETaO_(4)ceramics exhibit lower intrinsic thermal conductivity(2.98-1.23 W·m^(-1)·K^(-1),100-1000℃)and enhanced mechanical properties(6RETaO_(4),(9.97±2.2)GPa),which indicates that it is a potential material for thermal barrier coatings.