Phase Relations in the Ternary System Fe 2 O 3 —FeO—YFeO 3

Equilibrium data are presented for the ternary system Fe 2 O 3 –FeO–YFeO 3 in ambient atmospheres of air, oxygen, and carbon dioxide at melting temperatures. The temperature range for the coexistence of yttrium‐iron garnet and oxide liquid decreases with decreasing oxygen partial pressure from 127°C in oxygen to 86° C in air to 28° C in carbon dioxide. In addition, the composition of the garnet phase crystallizing from these melts changes with variations of temperature and oxygen pressure. The experimental data are discussed in terms of a polythermal‐polybaric model of the system. Some conclusions are drawn as to the limiting conditions in different atmospheres for the growth and the resulting composition of yttrium‐iron garnet crystals in equilibrium with ternary oxide liquids.