2A225

Crucibles having both of the following characteristics: 1. A volume of between 150 cm^3 and 8 000 cm^3; and 2. Made of or coated with any of the following materials, or combination of the following materials, having an overall impurity level of 2 % or less by weight: a. Calcium fluoride (CaF2); b. Calcium zirconate (metazirconate) (CaZrO3); c. Cerium sulphide (Ce2S3); d. Erbium oxide (erbia) (Er2O3); e. Hafnium oxide (hafnia) (HfO2); f. Magnesium oxide (MgO); g. Nitrided niobium-titanium-tungsten alloy (approximately 50 % Nb, 30 % Ti, 20 % W); h. Yttrium oxide (yttria) (Y2O3); or i. Zirconium oxide (zirconia) (ZrO2);

Crucibles having both of the following characteristics: 1. A volume of between 50 cm^3 and 2 000 cm^3; and 2. Made of or lined with tantalum, having a purity of 99,9 % or greater by weight;

Crucibles having all of the following characteristics: 1. A volume of between 50 cm^3 and 2 000 cm^3; 2. Made of or lined with tantalum, having a purity of 98 % or greater by weight; and 3. Coated with tantalum carbide, nitride, boride, or any combination thereof.