Spark Plasma Sintering of CSed Powders

The lattice parameters of the hexagonal p-SiAlON phase were calculated from the XRD peaks ofthe products by employing the least-squares method. The lattice parameter a was calculated from (100), (110), (20 0), (2 10), (3 0 0), and (310) peaks of P-SiAlON, and the lattice parameter c was calculated from the (101) peak using the calculated a value. The bulk density of the spark-plasma-sintered (SPSed) specimens was measured according to the Archimedean principle, using distilled water as the medium. The detailed experimental procedure was published in paper [11]. 

After SPS, the Si peaks disappeared and only peaks due to P-SiAlON were observed. One possible reason for the disappearance of Si after SPS would be the vaporization or dissolution of Si into the solid during the high-temperature and high-pressure sintering process. 

Pure P-SiAlONs were obtained through SPS, though the CSed powders were not pure P-SiAlON products. The bulk density was measured by the Archimedes principle, while theoretical density values were obtained from literature. The relative densities of the SPSed P-SiAlON with z= 1-3 were more than 99% of the 

In our study, the lattice parameters a and c were calculated from the XRD data while z was calculated by using the lattice parameter a. Evidently, the calculated z values were in agreement with the expected z values in the raw mixture, except for the product with z = 4. Unfortunately, the z value did not increase to 4 even after the CSed P-SiAlON with z = 3 was used as a diluent to synthesize P-SiAlON with z = 4. From these observations, it could be inferred that the stoichiometic 

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