Patent ID: 7531036

Claim:
A single crystal heat treatment method, comprising a step of heating a single crystal of a cerium-doped silicate compound represented by general formula (1) or (2) below in an oxygen-containing atmosphere, wherein the oxygen-containing atmosphere is an atmosphere having an oxygen concentration of 100 vol %, or an atmosphere containing nitrogen or an inert gas and having an oxygen concentration of 1 vol % or higher but less than 100 vol %, wherein the single crystal is heated at a temperature ranging from 300° C. to 1150° C. in the heating step Y 2−(x+y) Ln x Ce y SiO 5 (1) (wherein Ln represents at least one elemental species selected from a group consisting of elements belonging to the rare earth elements, x represents a numerical value from 0 to 2, and y represents a numerical value greater than 0 but less than or equal to 0.2) Gd 2−(z+w) Ln z Ce w SiO 5 (2) (wherein Ln represents at least one elemental species selected from a group consisting of elements belonging to the rare earth elements, z represents a numerical value greater than 0 but less than or equal to 2, and w represents a numerical value greater than 0 but less than or equal to 0.2).