Abstract
This work demonstrates the potential for practical scalable growth of complex garnets and evaluates the implications of a multicomponent composition in the optical quality and elemental distribution of a Czochralski-grown crystal. Our experimental approach was designed to elucidate the relation between a complex garnet composition (Lu1/4Yb1/4Y1/4Gd1/4)3Al5O12, crystal growth parameters, crystal structural, and elemental homogeneity. Our hypothesis is that combining multiple rare earths (REs) that will fractionally occupy the dodecahedral site in the aluminum garnet structure will result in a stable, single garnet compound that can be grown by the Czochralski method. Single-crystal and powder x-ray diffraction indicated a single garnet phase with an increasing unit cell volume from seed to tail. In addition, we propose that the pattern of elemental segregation will be based on the deviation of the ionic radius of each constituent RE from the average RE ionic radius of the multicomponent garnet. Electron probe microanalysis revealed that ions that are smaller than that average (Lu3+ and Yb3+) are preferentially incorporated in the crystal, while elements that are larger than that average (Gd3+) are rejected. The ionic radius of Y3+ is close to that average and yttrium segregation was minimal. The concentrations of the four REs are closer to stoichiometric on the tail end of the boule. Scanning electron microscopy and energy-dispersive x-ray spectroscopy analysis reveal Gd-rich inclusions with eutectic microstructures in the tail end of the boule.
