is the X-ray diffraction pattern of the Y3Al5O12 composite structure ceramics sintered at 1750 °C for 10 h. The peaks in the pattern match well with yttrium alumina garnet (Y3Al5O12, JCPDS 88-2048). This result indicates that the composition of the ceramics is Y3Al5O12 with garnet structure and no secondary phase was found.