Phase Equilibrium Studies in the System Iron Oxide‐Y 2 O 3 –Gd 2 O 3

Equilibrium data at liquidus temperatures are presented for compositions in the quaternary system Y‐Gd‐Fe‐O in ambient atmospheres of oxygen gas (p O2 , = 760 mm Hg), air (P O2 , = 159 mm Hg), and CO 2 (p O2 variable). Incongruent melting occurred in yttrium‐iron and gadolinium‐iron garnet phases and in all intermediate garnet solid solutions in the three oxygen pressure sections studied. Fractionation in the yttrium/gadolinium ratio between oxide liquid and crystalline garnet phases in the quaternary system was not observed experimentally, indicating that unzoned (Y,Gd) 3 Fe 5 O 12 crystals may be grown from a melt without special precautions to maintain a fixed Y/Gd ratio.