Phase Relations in the System Ce 2 O 3 –Ce 2 Si 2 O 7 in the Temperature Range 1150° to 1970°C in Reducing and Inert Atmospheres

The high‐temperature phase relations in the system Ce 2 O 3 ‐Ce 2 Si 2 O 7 have been studied in the temperature range 1150°–1970°C in inert and reducing atmospheres by conventional quenching and differential thermal analysis. Three eutectic reactions were found to occur at 1664°C and 27 mol% SiO 2 between Ce 2 O 3 and Ce 2 SiO 5 , at 1870°C and 54 mol% SiO 2 between Ce 2 SiO 5 and Ce 4.67 (SiO 4 ) 3 O, and at 1762°C and 65 mol% SiO 2 between Ce 4.67 (SiO 4 ) 3 O and Ce 2 Si 2 O 7 . Microstructural characteristics of the eutectic reactions were observed. Cerium pyrosilicate exhibits a polymorphic transformation at 1274°C. The binary compounds of this system were all found to melt congruently. The enthalpy and entropy of melting of these binary compounds were calculated from the initial slopes of their experimentally determined liquidus lines.