A high-entropy (Er0.25Y0.25Ho0.25Yb0.25)2Si2O7 ceramic with good thermal properties and water-vapor corrosion resistance

Abstract

A high-entropy rare-earth disilicate (Er_0.25Y_0.25Ho_0.25Yb_0.25)₂Si₂O₇ (hereinafter referred to as (EYHY)₂Si₂O₇) ceramic was synthesized by a heat treatment process combined with spark plasma sintering. According to the experimental results, (EYHY)₂Si₂O₇ presents good phase stability and low thermal conductivity ([1.48–2.35] W∙m⁻¹∙K⁻¹) from room temperature to 1200°C. Its coefficient of thermal expansion is (3.89–5.32) × 10⁻⁶ K⁻¹ from 200 to 1400°C, similar to SiC-based materials ([4.5–5.5] × 10⁻⁶ K⁻¹). Due to the multiple doping effects, (EYHY)₂Si₂O₇ exhibits outstanding corrosion resistance performance in water-vapor corrosion tests. Its weight loss is 1.79 mg/cm² after corrosion at 1600°C for 30 h in the presence of 50% H₂O-50% O₂, which is lower than the corresponding four single components Re₂Si₂O₇ (Er₂Si₂O₇, Y₂Si₂O₇, Ho₂Si₂O₇, and Yb₂Si₂O₇) under the same conditions. Therefore, high-entropy (EYHY)₂Si₂O₇ ceramics are regarded as potential environmental barrier coatings materials for SiC ceramic matrix composites.