Rare earth aluminate sintered compact and method for producing rare earth aluminate sintered compact

A method for producing a rare earth aluminate sintered compact, the method comprising:

• providing a raw material mixture obtained by mixing, in a liquid, an oxide particle containing at least one rare earth element Ln1 selected from the group consisting of Y, La, Lu, Gd, and Tb, an oxide particle containing Ce, an oxide particle containing Al, and optionally, an oxide particle containing at least one element M1 selected from Ga and Sc;
• drying the raw material mixture to form a raw material mixture powder;
• forming the raw material mixture powder to obtain a formed body;
• and
• firing the formed body at a temperature in a range from 1300° C. to 1800° C. to obtain a sintered compact, wherein
• in the provision of the raw material mixture, a specific surface area, measured by a BET method, of at least one oxide particle selected from the oxide particle containing Ln1, the oxide particle containing Ce, the oxide particle containing Al, and the oxide particle containing the element M1 is 5 m2/g or greater,
• wherein the raw material mixture further comprises rare earth aluminate phosphor particles formed by a co-precipitation method and having a specific surface area as measured by the BET method that is 5 m2/g or greater and not greater than 12 m2/g.