Silicon carbide block found on TaoBao

Interesting to find TB offering a "transparent" block 

Looks like for semiconductor back support substrate.

Is it good for optical purpose?

Some of spec:

Claim transparency to be 60-70% ??

For 6 inch, 20mm, it's claimed to be 1100 g, ie density 3.0 g/cm3

Vs borosilicate glass of 2.23

Expansion( in theory):

从室温到1000°C，c轴的热膨胀系数可能从约4.0×10⁻⁶ /K增加到约5.5×10⁻⁶ /K。

这个没有检测数据，是理论值.

>>> All these are prototypes quality, maybe even scraps from tests, and no thorough testing according to the specs.!!!