Phase Relations in the System Al 2 O 3 ─Ce 2 Si 2 O 7 in the Temperature Range 900° to 1925°C in Inert Atmosphere

Equilibrium relationships in the system Al 2 O 3 ‐Ce 2 Si 2 O 7 in inert atmosphere have been investigated in the temperature range 900° to 1925°C. A simple eutectic reaction was found at 1375°C and 51 mol% Ce 2 Si 2 O 7 . A high‐low polymorphic transformation in Ce 2 Si 2 O 7 was observed at 1274°C. New XRD patterns are suggested for both polymorphs of cerium pyrosilicate. The melting point of Ce 2 Si 2 O 7 was found to be 1788°C. A value for ΔH° m,Ce2Si2O7 of 36.81 kJ/mol was calculated from the initial slope of the experimentally determined liquidus in equilibrium with the pyrosilicate phase.