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Detailed Program
Paper Number : EF-I03
Time Frame : 15:50~16:15
Presentation Date : Friday, 28, November
Session Name : Electric Field Assisted Sintering
Session Chair 1# : Young-Hwan Han
Session Chair 2# : Tetsuo Uchikoshi
Spark-Plasma-Sintering (SPS) of Transparent MgAl2O4 Spinel
Koji MORITA
National Institute for Materials Science
In order to attain transmission in oxide ceramics, reducing the residual porosity is regarded as a key factors because the pores act as a main light scattering source. Pressure assisted sintering techniques, such as hot pressing (HP) and/or hot isostatic pressing (HIP), has generally been employed for attaining fully dense ceramics. More recently, instead of the HP or HIP techniques, spark-plasma-sintering (SPS) technique has been applied to the fabrication of various transparent oxide ceramics, such as -Al2O3, MgAl2O4 spinel, MgO, YAG and ZrO2. The primary reason is that, as compared with the well-known HP or HIP techniques, the SPS technique can utilize high heating rates higher than 50¡ÆC/min, and hence, can save the total processing time of powder densification.
The densification, however, is known to be highly sensitive to the SPS conditions, such as heating rate, temperature, holding time and loading schedule. For the fabrication of transparent -Al2O3 and spinel ceramics, for example, a low heating rate of 10¡ÆC/min is highly effective than the widely used high heating rates of 50¡ÆC/min. In order to apply the SPS processing to the fabrication of transparent ceramics, optimization of the SPS processing is necessary. For example, the carbon contamination arises from the trace CO3 impurities pre-existing in the starting powder, irrespective of the SPS conditions. For the higher heating rate, which is the primary advantage of the SPS technique, the additional carbon contamination occurred from the paper/die used in the SPS processing and remained as glassy carbon phases in the matrix. Oxygen vacancies are also introduced into the spinel matrix depending on the SPS condition. In the presentation, we will introduce the recent data of the transparent spinel and will discuss the effect of the SPS conditions on the fabrication of transparent spinel.
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