Coupled substitution of gallium by magnesium and zirconium in single crystals of gadolinium gallium garnet

Abstract

Single crystals of gadolinium gallium garnet in which the gallium ions on the octahedral sites were partially substituted by coupled substitution of magnesium and zirconium have been grown using the Czochralski technique. Single crystals of 36 mm in diameter and 100 mm in length corresponding to the formula Gd 3Ga 5- x- y Mg x Zr y O 12 have been obtained from melt compositions in which 0.1 ⩽ x = y ⩽ 0.7. The dislocation and inclusion densities of the single crystals are below 5 cm -2. The lattice parameters increase linearly from 12.382 Å for gadolinium gallium garnet to 12.489 Å for x = y ≈ 0.54. The distribution coefficient increases in this concentration range from K eff = 0.58 to K eff = 0.89. Boules grown from melt compositions in which x = y ⩾ 0.7 appear cloudy through precipitation of Gd 2Zr 2O 7 as a second phase.