Single crystal growth in the Ga-Pd system

Abstract Single crystal growth of the intermetallic compounds GaPd 2 , GaPd, and Ga 7 Pd 3 is described for the first time. These phases have recently been explored as highly selective heterogeneous catalysts in the semi-hydrogenation of acetylene. Well-oriented single-crystalline surfaces are needed to perform fundamental studies on catalytic processes. The three Ga–Pd phases were grown using the Czochralski method from Ga-rich solutions. Thermodynamic properties of the Ga–Pd system determine very different growth temperatures reaching from less than 460 °C for Ga 7 Pd 3 to about 1200 °C for GaPd 2 . Avoiding mother liquid inclusion formation proved to be the key problem that could be solved by pulling rates sometimes as low as 25 µm/h and forced convection by high crystal rotation rates. In the last grown part of GaPd 2 crystals decomposition into GaPd 2 /Ga 3 Pd 5 lamellas occurred which can be explained either by spinodal decomposition or by nucleation caused by the GaPd 2 stability region that becomes narrower with decreasing temperatures.