Engineering stoichiometry of high entropy fluorite oxide to obtain optimized thermophysical property and improved corrosion resistance

Engineering stoichiometry of materials is an effective strategy to optimize the comprehensive properties. Here we prepare high-entropy Er₂(Y_0.2Yb_0.2Nb_0.2Ta_0.2Ce_x)₂O_δ with single-phase fluorite structure by a solid-state reaction. The effects of stoichiometry of cerium on thermophysical properties and corrosion resistance to calcium−magnesium−alumina−silicate (CMAS) of the high-entropy oxides have been investigated. By engineering the cerium stoichiometry, thermal conductivity increases slightly from 1.21 to 1.36 W·m⁻¹·K⁻¹ and thermal expansion coefficients also increases from 10.56 × 10⁻⁶ to 11.61 × 10⁻⁶ °C⁻¹ at 1000 °C. Furthermore, corrosion resistance of the high-entropy Er₂(Nb_0.2Ta_0.2Y_0.2Yb_0.2Ce_x)₂O_δ improves with the increase of cerium content. The effects of cerium content on CMAS resistance have been discussed in detail. Our work reveals that engineering stoichiometry of high-entropy oxides is expected to be an effective strategy to broaden the compositional space and optimize the thermophysical properties and CMAS corrosion resistance.