PURPOSE: To inexpensively obtain the spinel sintered body for ornamentation which has an excellent transparent feel and has the optical characteristics approximate to the optical characteristics of natural spinel by sintering spinel powder by hot pressing under specific conditions and subjecting the sintered body to an HIP treatment under specific conditions.
CONSTITUTION: The spinel powder having ≥99.5% purity and ≥102/g specific surface area (BET value) is sintered by hot press in a vacuum at 1200 to 1700°C and under 100 to 500kg/cm2 pressure. The sintered body obtd. in such a manner is subjected to the HIP treatment at 1450 to 1800°C and under ≥550kg/cm2 pressure by using an inert gas, gaseous nitrogen or gaseous oxygen or the gaseous mixture composed thereof to obtain the desired spinel sintered body. The high-purity spinel powder to be used is adequately the spinel powder formed by hydrolysis of alkoxide, etc. This spinel sintered body is useful as an original stone for ornamentation, such as jewels, even when the sintered body is not colored. Since MgO and Al2O3, etc., are equal in mol, the beautiful colors of the dark red colors similar to the colors of natural spinel are obtd. even if this spinel is colored by addition of Co, etc., thereto.
SHIBATA KENICHIRO
TSUJI KAZUO
