A Comprehensive Study of the Carbon Contamination in Tellurite Glasses and Glass‐Ceramics Sintered by Spark Plasma Sintering (SPS)

Abstract

Highly transparent tellurite glasses and glass‐ceramics based on the 85TeO2–15WO3 composition (mol%) were produced by spark plasma sintering (SPS) from powders previously prepared by the conventional melt‐quenching technique and then grinded. We report a study based on the understanding of carbon contamination that is commonly observed by this nonconventional sintering technique and which constitutes a drawback for optical applications. First, the influence of the particle size of the initial amorphous powders as well as an additional pressureless sintering step prior to SPS experiments and the use of a physical carbon diffusion barrier have been investigated to reduce the carbon contamination in glass bulks. Second, once reducing the carbon contamination, glass‐ceramics were obtained by varying the SPS conditions. The noncentrosymmetric γ‐TeO2 phase crystallized within the bulk volume while maintaining good optical transparency and led to the generation of second harmonic. This approach paves the way to further applications in the domain of linear and nonlinear optics.

Spectroscopic study of the discoloration of transparent MgAl2O4 spinel fabricated by spark-plasma-sintering (SPS) processing

“…3d) must take place at the high heating rates during the heating process of T < 1300°C, at which the open pores remain [15,55]. Bertrand et al [69] also suggest that the interaction between carbon and residual oxygen occurs during the heating and densification, when an open pore system is present. Consequently, it is reasonable to explain that the additional carbon contamination occurs mainly by the evaporation of the carbon phase during the heating process of T < 1300°C.…”

The effect of spark plasma sintering on lithium disilicate glass-ceramics

“…Removal of this layer using CAM may be one solution. In a detailed investigation of carbon contamination in tellurite optical glasses a pressureless sintering step around T g before the SPS was suggested as the most efficient to avoid large graphite pollution in the final sintered specimens [23]. Identification of new materials to replace the graphite die assembly or use of molybdenum foils to line the assembly may avoid microstructural inclusions and the possibility of reduced translucency by superficial surface contamination.…”

Synthesis of nanostructured iron oxides and new magnetic ceramics using sol-gel and SPS techniques

“…However, carbon phase (graphite) was indicated in the composition of ceramics obtained above 800ºC. Emergence of free carbon in the SPS composites was remarked by many researchers earlier and it is caused by presence of carbon in the electrode composition, molds, isolation paper and other components [31,32]. Thus, carbon, removed by spark plasma from the surface of working units, diffuse both over the surface and throughout the whole volume of consolidated material.…”