Preparation of dense amorphous Al2O3–ZrO2–Y2O3 by two-step hot pressing

Two-step hot pressing was reported for the first time in the densification of amorphous oxides. Amorphous AZY powder was synthesized by sol–gel method, and densified by conventional hot pressing (CHP) and two-step hot pressing (TSHP). In CHP, the sample was easily crystallized and the maximum realizable density was 93.5% under 350 °C for 1 min before crystallization. In TSHP, uniform amorphous AZY with relative density up to 98% was achieved under T1 = 350 °C, T2 = 200 °C for 15 min. Based on the key problem in preparation of dense bulk amorphous oxides, TSHP solved the competition between densification with crystallization, and provided new methods to densification of amorphous oxides.