Fast grain growth phenomenon in high-entropy ceramics: A case study in rare-earth hexaaluminates

It is generally reported that the grain growth in high-entropy ceramics at high temperatures relatively slower than corresponding single-component owing to so-called sluggish diffusion effect. In this study, we report a fast phenomenon (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)MgAl11O19 (HEMA) prepared by conventional solid-state reaction method. The results demonstrate sizes of as-sintered HEMA are larger those five same pressureless sintering process, and rate obviously higher during subsequent heat treatment. Such indicates effect cannot dominate behavior current ceramics. X-ray photoelectron spectroscopy (XPS) analysis reveals there more oxygen vacancies (OV) variable valance states Eu ion. high-temperature electrical conductivities support analysis. considered concentration OV its mobility contribute accelerated migration cations consequently increase rate. Based on it believed multiple intrinsic factors for ceramic system will simultaneously determine temperatures.