Inhibition of hotspot formation by alumina addition in flash sintering of (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 high-entropy ceramic

Sintering inhomogeneities caused by hotspots are one of the factors hindering the development of flash sintering technology. Herein, to overcome this problem for a high-entropy pyrochlore-structured (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 ceramic (abbreviated as RE2Zr2O7), we propose a simple strategy, namely, addition of Al2O3 to the ceramic and achieved a significant effect. During flash sintering, rare earth ions in RE2Zr2O7 reacted with Al2O3 to form REAlO3 and RE2−xZr2O7–3x/2, which substantially improved the sintering homogeneity. With an increase in the Al2O3 content, REAlO3 transformed into REAl11O18. The crack deflection and bridging effect caused by the formation of these phases and their intrinsic high hardness and high modulus improved the mechanical properties of the composite ceramic. The use of an internal reaction to improve the electrical conductivity of a ceramic body is an economical and effective strategy to prevent hotspot formation during flash sintering.