Optical properties of SPS-ed Y- and (Dy,Y)-α-sialon ceramics

Y 0.67 Si 9 Al 3 ON 15 and Dy 0.4 Y 0.3 Si 8.85 Al 3.15 O 1.05 N 14.95 ceramics were prepared by Spark Plasma Sintering (SPS) with and without heat treatment at 1700°C for 7 h or 17 h, and their optical transmittance were investigated over the wavenumber range 4000–1500 cm −1 . The results showed that the assemblages of the SPS-ed samples consisted of single crystallized α-sialon phase in both compositions. EDS analysis indicated that α-sialon was mainly stabilized by Dy 3+ in the multi-cation (Dy,Y)-α-sialon composition. The SPS-ed specimens showed relatively high optical transmission properties, and the maximum transmittance reached around 65% at 2800 cm −1 for 0.5 mm thick specimens of both compositions. The 7 h heat treatment caused the formation of small amount of melilite phase, resulting in non-uniform microstructure and decrease in optical transmittance. Extended heat treatment for 17 h led to more homogenous microstructure and increased the transmittance to some extent. Less melilite was formed in the multi-cation (Dy,Y)-α-sialon composition than in the single cation Y-α-sialon after heat treatment, and the transmittance of (Dy,Y)-α-sialon was also higher than that of Y-α-sialon.