| 摘要 |
PURPOSE:To form colorless and transparent cubic zirconia by using a graphite material having prescribed amounts or less of ash content, among them, especially a prescribed amount or less of the sum total of V, Cr, Fe, Ti, Ni, Co and Cu. CONSTITUTION:The interior of a Cu crucible equipped with pipes arranged for circulating cooling water is filled with ZrO2 powder according to a skull melting method and high-purity graphite materials having <=10ppm total ash content, among them, especially <=5ppm sum total of V, Cr, Fe, Ti, Ni, Co and Cu contents as heating elements are inserted thereinto. A high-frequency electric power is then applied to dielectrically heat the heating elements. The ZrO2 powder is converted into a molten state to slowly grow a crystal from the bottom thereof. Cooling is subsequently carried out to take out the crystal, which is polished to afford the objective colorless transparent cubic zirconia in high yield. |
