Rare-earth zirconates with pyrochlore and fluorite structures have recently been identified as promising thermal barrier coating materials owing to their low thermal conductivities. In this study, six samples with the general formula (NdSmEuGd)_1-xDy_2xZr₂O₇ were synthesized to further reduce the thermal conductivity. X-ray diffraction and Raman spectroscopy showed that the transition from an ordered pyrochlore to a disordered fluorite structure is due to cation and anion disorder. Transmission electron microscopy showed that anion disorder occurred before cation disorder. A modified mass disorder parameter was introduced into this system, which can describe the change in thermal conductivity well. This parameter can be a basis for designing more complex materials with lower thermal conductivities.

In this study, the water vapor corrosion resistance of two types of high-entropy pyrosilicates ((Yb_0.2Y_0.2Lu_0.2Ho_0.2Er_0.2)₂Si₂O₇ ((5RE_1/5)₂Si₂O₇) and (Yb_0.25Lu_0.25Ho_0.25Er_0.25)₂Si₂O₇ ((4RE_1/4)₂Si₂O₇)) and two single-component pyrosilicates (Yb₂Si₂O₇ and Lu₂Si₂O₇) were evaluated at 1350 ℃ for 50–100 h, and the initial corrosion behaviors of these pyrosilicates were studied. The results showed that the final corrosion products of the four types of pyrosilicates were all X2-type monosilicates, exhibiting similar corrosion phenomena. However, (4RE_1/4)₂Si₂O₇ generated many nanoscale monosilicate grains during corrosion. The corrosion resistance of Lu₂Si₂O₇ was clearly better than those of the others, and (4RE_1/4)₂Si₂O₇ exhibited the worst corrosion resistance. The corrosion mechanism of the pyrosilicate blocks was analyzed from the perspectives of grain size, bulk hydrophobicity, and binding energy. This study potentially provides a theoretical basis for the preparation of high-entropy pyrosilicates with different atomic ratios according to the different properties of the various rare earth elements.