Subsolidus Phase Relationships in Part of the System Si,Al,Y/N,O: The System Si 3 N 4 ─AIN─YN─Al 2 O 3 ─Y 2 O 3

The subsolidus phase relationships in the system Si,Al,Y/N,O were determined. Thirty‐nine compatibility tetrahedra were established in the region Si 3 N 4 ─AIN─Al 2 O 3 ─Y 2 O 3 . The subsolidus phase relationships in the region Si 3 N 4 ─AIN─YN─Y 2 O 3 have also been studied. Only one compound, 2YN:Si 3 N 4 , was confirmed in the binary system Si 3 N 4 ─YN. The solubility limits of the α′─SiAION on the Si 3 N 4 ─YN:3AIN join were determined to range from m = 1.3 to m = 2.4 in the formula Y m /3 Si 12‐ m Al m N 16 . No quinary compound was found. Seven compatibility tetrahedra were established in the region Si 3 N 4 ─AIN─YN─Y 2 O 3 .