Mechanism of Carbon Contamination in Transparent MgAl2O4 and Y3Al5O12 Ceramics Sintered by Spark Plasma Sintering

An investigation of MgAl2O4 spinel and Y3Al2O5 (YAG) materials sintered by spark plasma sintering (SPS) was performed. The optical properties of the materials are modified depending on the powder source and the SPS sintering conditions. Spectrophotometer and Raman analysis are presented in this work, along with optical and scanning electron microscope (SEM) observations and cathodoluminescence analysis. The results show a correlation between carbon contamination and the optical properties of the materials. Herein, the source of the contamination is explained, along with its genesis and diffusion. The carbon contamination originates from the powder itself (carbonates), as well as the SPS environment (papiex(R) graphite foil, graphite die, graphite felt) to form carbon clusters. During the high-temperature SPS process, carbon from those carbon clusters diffuses, resulting in an increase in the contamination volume, thereby increasing the light absorption.