Schwerin, J.; Müller, D.; Kiese, S.; Gille, Peter
Single crystal growth in the Ga-Pd system.
In: Journal of Crystal Growth
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Single crystal growth of the intermetallic compounds GaPd2, GaPd, and Ga7Pd3 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 Ga7Pd3 to about 1200 °C for GaPd2. 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 GaPd2 crystals decomposition into GaPd2/Ga3Pd5 lamellas occurred which can be explained either by spinodal decomposition or by nucleation caused by the GaPd2 stability region that becomes narrower with decreasing temperatures.