Patent ID: 9052415
Filing Date: 2015-06-09
Classification: C01F,C01P,C04B,G02B,G02F

Abstract:
1. A method for selecting a magneto-optical ceramic material having a high extinction ratio, comprising a step of selecting an oxide ceramic material wherein the difference between the refractive index at a grain boundary and the refractive index of a main phase of the oxide ceramic crystal at 25° C. is not more than 0.004 as a magneto-optical ceramic material having an extinction ratio of at least 30 dB, from oxide ceramic materials based on an oxide having the formula (1): wherein Re is at least one element selected from the group consisting of scandium, yttrium, lanthanum, europium, gadolinium, ytterbium, holmium and lutetium, and 0.4≦x≦1.0, wherein the oxide ceramic materials based on an oxide having the above formula (1) are prepared by using a terbium oxide and an oxide of at least one rare earth element selected from the group consisting of scandium, yttrium, lanthanum, europium, gadolinium, ytterbium, holmium and lutetium as main components, adding one or more sintering aids thereto, mixing, molding, calcining, sintering in vacuum, and hot isostatic pressing, wherein the difference between the refractive index at the grain boundary and the refractive index of the main phase of the oxide ceramic crystal at 25° C. is measured by steps of directing measurement light to a microscopic spot of the measurement surface of the oxide ceramic material via an objective lens while moving the oxide ceramic material, detecting the intensity of the reflected light corresponding to the position of the measurement surface by a photodetector continuously, and counting a change of refractive index based on a change of the photodetector signal as the difference in refractive index between the grain boundary and the main phase of the oxide ceramic crystal.