Distribution coefficients for rare-earth doping in Y3Ga5O12 garnet: Comparison with Y3Al5O12

We present the distribution coefficient k in Y3Ga5O12 garnet (YGG) for a series of rare-earth dopants (RE = La, Ce, Nd, Eu, Tb, Er, and Lu), and compare the results with our previous data on RE-doped Y3Al5O12 garnet (YAG). Under our condition of flux growth, single crystals of undoped YGG show the shape of pure trapezohedron with {211} faces, whereas RE doping stabilizes {110} faces. This is to be compared with the case of YAG, where {110} was the dominant face in both undoped and RE-doped crystals. In RE-doped YGG, k remains near unity when the size mismatch between the dopant and host Y3+ ions is within about 3-4%, and drops off rapidly for larger dopants. This is in contrast to RE-doped YAG, where k decreases continuously from the smallest (Lu3+) to the largest (La3+) dopant. We find such distinct behaviors to be correlated with the reported solution energies for the series of RE ions in YAG and YGG.