Abstract: A rare earth garnet sintered compact which is produced by subjecting a rare earth garnet powder such as YAG to a pre-sintering, sintering the pre-sintered product by HIP, and annealing the sintered product at 1100° C. to 1600° C. in a whole oxygen atmosphere under a whole pressure of 4.5 MPa or more, and has an average crystallite diameter of 0.9 to 9 ?m, an optical loss coefficient of 0.002 cm?1 or less and a strain of a transmitted wave of 0.05 ? cm?1 or less.

Abstract: A rare earth garnet sintered compact which is produced by subjecting a rare earth garnet powder such as YAG to a pre-sintering, sintering the pre-sintered product by HIP, and annealing the sintered product at 1100° C. to 1600° C. in a whole oxygen atmosphere under a whole pressure of 4.5 MPa or more, and has an average crystallite diameter of 0.9 to 9 ?m, an optical loss coefficient of 0.002 cm?1 or less and a strain of a transmitted wave of 0.05 ? cm?1 or less.

Abstract: A high-purity rare earth metal oxide material powder of purity of 99.9% or over, of which Al content is 5-100 wtppm in metal weight and Si content is 10 wtppm or under in metal weight, and a binder are used to prepare a molding body of which molding density is 58% or over of the theoretical density. The binder is eliminated by thermal treatment, and then the molding body is sintered in an atmosphere of hydrogen or a rare gas or a mixture of them or in a vacuum at a temperature being not lower than 1450° C. and not higher than 1700° C. for 0.5 hour or over to prepare A transparent sintered rare earth metal oxide body represented by a general formula R2O3 (R being at least one element of a group comprising Y, Dy, Ho, Er, Tm, Yb and Lu).

Abstract: A high-purity rare earth metal oxide material powder of purity of 99.9% or over, of which Al content is 5-100 wtppm in metal weight and Si content is 10 wtppm or under in metal weight, and a binder are used to prepare a molding body of which molding density is 58% or over of the theoretical density. The binder is eliminated by thermal treatment, and then the molding body is sintered in an atmosphere of hydrogen or a rare gas or a mixture of them or in a vacuum at a temperature being not lower than 1450° C. and not higher than 1700° C. for 0.5 hour or over to prepare A transparent sintered rare earth metal oxide body represented by a general formula R2O3 (R being at least one element of a group comprising Y, Dy, Ho, Er, Tm, Yb and Lu).