High‐entropy transparent (Eu 0.2 Gd 0.2 Y 0.2 Yb 0.2 Lu 0.2 ) 3 Al 5 O 12 ‐based nanoceramics elaborated from full glass crystallization

Abstract Garnet‐structured (A 3 B 5 O 12 ) transparent ceramics show promising applications in fields such as lasers, phosphors, and scintillators. The introduction of high‐entropy design into transparent ceramics offers a new pathway to expand the regulatory space of structure and properties in garnet materials. However, conventional powder sintering methods used for preparing high‐entropy transparent ceramics face several challenges, including stringent requirements for high‐quality powders, dependence on high temperature and pressure, and consequently grain coarsening. In this study, we innovatively employed the full glass crystallization method to fabricate high‐entropy transparent ceramics. Through pressureless crystallization of glassy bulk at a relatively low temperature (1000°C, 2 h), a high‐entropy transparent (Eu 0.2 Gd 0.2 Y 0.2 Yb 0.2 Lu 0.2 ) 3 Al 5 O 12 ‐Al 2 O 3 (HEAG‐Al 2 O 3 ) garnet‐based nanoceramic was successfully synthesized. Crystallization kinetics analysis revealed that the bulk glass precursor of the HEAG‐Al 2 O 3 nanoceramic exhibits a high activation energy, with a crystallization mechanism of three‐dimensional crystal growth mode accompanied by volume nucleation. The obtained high‐entropy transparent ceramic consists of a HEAG primary phase and an in‐situ formed Al 2 O 3 secondary phase. The resulting dense three‐dimensional network nanostructure, combined with nanoscale grains (< 30 nm), endow the biphasic HEAG‐Al 2 O 3 nanoceramics possessing excellent optical transmittance (81.4% at 780 nm) and mechanical properties even comparable to those of single crystal.