Spark plasma sintering of transparent YAG ceramics assisted by the YAH–YAG phase transformation

Transparent YAG ceramics have been prepared by spark plasma sintering assisted by a phase transformation from the metastable YAH to the stable YAG. During sintering process, the YAH phase transforms to the YAG phase accompanied by particle arrangement at 920 °C, which leads to the enhancement of densification. Moreover, the effect of the applied pressure on phase transformation was also studied. It is demonstrated that the applied pressure could accelerate the phase transformation that result in the increased densification rates. At low-temperature 920 °C under 80 MPa, the specimen was fabricated with the in-line transmittance of 44% at 680 nm and 66% at 1000 nm, and its average grain size was about 380 nm.