Ultra-low thermal conductivity and enhanced mechanical properties of high-entropy rare earth niobates (RE3NbO7, RE = Dy, Y, Ho, Er, Yb)

A new entropy-stabilized rare earth niobates (RE3NbO7, RE = Dy, Y, Ho, Er, Yb) system with disordered defective fluorite structure was prepared by solid-state method. XRD, Raman and EDS results confirmed the homogeneous distribution and equimolar doping of rare earth cations. High-entropy RE3NbO7 ceramics showed smaller grain size compared with single rare earth niobates owing to the sluggish grain diffusion. Due to the increased configuration entropy, (Dy0.2Ho0.2Er0.2Y0.2Yb0.2)(3)NbO7 (5RE(3)NbO(7)) has enhanced mechanical properties (H-v = 9.51 GPa, K-IC = 2.13 MPa m(0.5)), a high thermal expansion coefficient (10.2 x 10(-6) K-1, 1200 degrees C) and ultra-low thermal conductivity (0.724 W m(-1) K-1, 25 degrees C). These results suggest that the material can be used as a new type of thermal barrier coatings as alternative to yttria-stabilized zirconia.

Automated summary

A novel high-entropy rare earth niobates material has been prepared, showing superior mechanical properties, high thermal expansion coefficient, and ultra-low thermal conductivity, making it a potential alternative for traditional yttria-stabilized zirconia as a new type of thermal barrier coating.