Refractory Technology
Beryllia (which is used in making crucibles for melting uranium & thorium) is superior to alumina in all respects for high temperature (> 1900°C ) use, except

Thermal conductivity
Electrical conductivity
Fusion point
Cost

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Refractory Technology
What is Thoria?

All of these
Thoria Has high fusion temperature (> 3000°C) but poor resistance to thermal shock
Which is expensive & radioactive, is used in crucibles for melting high purity metals
Thoria Has high resistance to basic slags

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Refractory Technology
Silica refractories

All of these
Have lower thermal conductivity than fireclay bricks
Can not be used in the dome of hot blast stoves
Crack when subjected to sudden change of temperature

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