Heating methodology




Resistance heating

Simple, practical, cheap

Difficult in control of zone length; more risk on contamination from container

Most common heating element; more suitable for small charges with modest melting point

(less than 500˚C)

Induction heating

Providing higher power; Shorter zone can be established; providing stirring degree; less possibility of contamination from container

Occupy more floor space; expensive; power probably changing sharply as the variation of position, conductivity, and thickness of the charge

Semiconductors and most metals

Electrical discharge

Melt the refractory metal

Demand on vacuum system; expensive

Refractory metals

Radiation heating

More feasible to get short zone length; less possibility of contamination from container; possible to melt refractory metals

Need one pair of spherical concave mirror; Occupy more floor space; precise radiation path and focus

Most Metals