SPS Processed Transparent Ceramics

1000 °C for 10 min, the sintered disk was about 30 mm in diameter and 3 mm in thickness. In addition, for the heating rates of 8 and 50 °C min, sintering time was varied between 0 and 5 h, in order to examine the grain growth behavior. The mechanical pressure was unloaded before annealing. 

It is possible to further optimize the sintering effectiveness and efficiency when using SPS. For example, a two-step pressure profile was used to demonstrate the feasibility of SPS in processing MgAl204 [140]. At a low preload pressure, 5 MPa, with a normal fast heating rate of 100 °C min samples could have high in-line transmittance of 51 % at 550 nm and 85 % at 2000 nm. Sintering was carried out in 

NIMS NIMS NIMS NIMS NIMS NIMS NIIVIJ IIV Ml h J 

21 In-line transmission of the alumina sintered at 1150 °C for 20 min. The sample thickness is about 0.9 mm. Reproduced with permission from [138]. Copyright 2009, Elsevier 

The one sintered at 1573 K after annealing reached nearly 99 % of the theoretical value in the infrared region, as shown in Fig. 7.26a. This temperature was much lower than those required by other sintering techniques. 

---

Frage N, Kalabukhov S, Sverdlov N, Ezersky V, Dariel MP (2010) Densification of transparent yttrium aluminum garnet (YAG) by SPS processing. J Eur Ceram Soc 30 3331-3337... 

Meir S, Kalabukhov S, Froumin N, Dariel MP, Frage N (2009) Synthesis and densification of transparent magnesium aluminate spinel by SPS processing. J Am Ceram Soc 92 358—364 Frage N, Cohen S, Meir S, Kalabukhov S, Dariel MP (2007) Spark plasma sintering (SPS) of transparent magnesium-aluminate spineL J Mater Sci 42 3273-3275... 

Although the studies on simulations of densification behaviors of transparent ceramics by using EGAS (SPS) process have not been widely reported, the results that have been discussed above can be used as a reference. This is especially true for those of oxide materials, because they share similar thermophysical properties with transparent ceramics. 

Fig. 7.36 Photographs (top) and TEM image (bottom) of the Yb -doped Sr5(P04)3p transparent ceramics processed by using SPS. Reproduced with permission from [149]. Copyright 2012, John Wiley Sons...

---