Rapid preparation of traditional and high-entropy garnet ceramics by SPS at low temperature with ultrafast densification

Spark plasma sintering (SPS) is a fast and efficient method for preparing functional ceramics . This article investigates the phase evolution, thermal expansion and chemical stability of traditional (Y 1.2 Nd 1.8 Fe 5 O 12 ) and high-entropy ((Y, Gd, Sm, Eu, Dy) 3 Fe 5 O 12 ) garnet ceramics. Prepared under conventional SPS (50 MPa) conditions at 900–1100 °C. The results indicate that using SPS sintering method can significantly reduce the sintering temperature (1100 °C) and time (3 min) of garnet ceramics. (Y, Gd, Sm, Eu, Dy) 3 Fe 5 O 12 (1.6 × 10 −6  K −1 ) exhibits superior thermal expansion stability compared to Y 1.2 Nd 1.8 Fe 5 O 12 (5.4 × 10 −6  K −1 ). The strong REE-O bond energy and severe lattice distortion of high entropy garnet ceramics hinder the migration and diffusion of cations, resulting in higher leaching resistance of high-entropy garnet ceramics (∼10 −7  g m −2  d −1 -10 −8  g m −2  d −1 ) compared to traditional garnet ceramics (∼10 −5  g m −2  d −1 -10 −6  g m −2  d −1 ). Therefore, SPS has broad application prospects in the low-temperature preparation of high-entropy garnet ceramics for immobilization of actinide elements.