For optimal performance the correct crucible liner is imperative, Process Materials offers Alumina Al2O3, Intermetallic BN-TiB2, Copper, Tantalum, Graphite, Tungsten, Boron Nitride, Molybdenum, and Vitreous Coated Carbon.
Thermal shock is the most common reason crucible liners crack, always be sure to fill the liner appropriately. Some materials become highly reactive when molten and may alloy to the liner (see your sales engineer for help when choosing the correct liner).
