Characteristic Imperfections in Flux‐Grown Crystals of Yttrium Iron Garnet

Crystals of yttrium iron garnet grown from lead oxide and lead oxide‐lead fluoride flux systems are inhomogeneous and contain characteristic imperfections that may be significant in the evaluation of physical properties. A petrographic study of single‐crystal sections has revealed dendritic nuclei, oriented layers of submicroscopic foreign material located in the outer regions of the crystals, and oriented occlusions in intermediate positions. Changes in the appearance of thin sections resulting from the use of an oxygen atmosphere during synthesis combined with other observations indicate that divalent iron contributes to inhomogeneities and imperfections present in yttrium iron garnet crystals. Growth mechanisms involving an initial dendritic stage with (100) and (111) fast‐growth directions followed by layered growth parallel to major crystal planes, normally (110) and (211), can be deduced from the appearance and location of crystal imperfections.