1：Experimental Design and Method Selection:

The study employed a solid-state reaction method to synthesize AlON powders from Al2O3 and AlN powders, focusing on reducing synthesis temperature and time. The method involved ball-milling to reduce particle size and improve homogeneity, followed by calcination and sintering.

2：Sample Selection and Data Sources:

Raw materials included nanometre-sized Al2O3 powder (mean diameter D50: ~150 nm) and micrometre-sized AlN powder (D50: ~3 μm), both from St-Nano Science & Technology Co., Ltd. Mixtures were prepared with varying AlN mole ratios (68-80% Al2O3).

3：3). List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included a ball mill with nylon jar and alumina balls, graphite furnace, pyrometer, TempCheks for temperature calibration, laser particle size analyser (MS 3000, Malvern Instruments Ltd.), X-ray diffractometer (DX-2700, Dangdong Fangyuan Instruments Co., Ltd.), scanning electron microscope with EDS (Phenom XL, Phenom World Ltd.), and spectrometers (Cary 630 FTIR and Cary 6000i, Agilent Technologies). Materials included high purity alumina balls, absolute ethyl alcohol, and Y2O3 powder.

4：Experimental Procedures and Operational Workflow:

AlN powder was first ball-milled to reduce particle size, then mixed with Al2O3 and ball-milled again. The mixture was dried, ground, sieved, and calcined in a graphite furnace under nitrogen atmosphere at temperatures from 1620-1700 °C for 10-120 min. Resulting powders were treated to remove carbon contaminants, ball-milled, dried, sieved, mixed with Y2O3, pressed into pellets, and sintered pressurelessly at 1950 °C for 12 h. Final ceramics were ground and polished.

5：Data Analysis Methods:

Phase composition was analyzed using XRD, particle size and distribution with laser particle size analyser, microstructure and elemental mapping with SEM and EDS, and optical transmittance with spectrometers.