Conventional catalysts for heterogeneous catalysis usually consist of finely dispersed particles of noble metals or their alloys on an oxide support material. Recent research has shown that also intermetallic compounds have a high potential as good catalysts being highly active with respect to a specific reaction and showing advantages in long-term stability and selectivity. For instance this was found for Pd-Ga intermetallic compounds used as semi-hydrogenation catalysts [1]. Due to the well-ordered crystal structure of the intermetallic compounds segregation effects are avoided and isolation of the active sites is assured (active-site isolation concept [2]).

The intermetallic compound InPd (CsCl prototype, Pm3m) is a promising catalyst material for methanol steam reforming. This reaction is a possibility to produce hydrogen for fuel cells in-situ from methanol. So the problems of storage and transportation of hydrogen could be avoided.

In order to understand the basic mechanisms of the catalysis and to enable a knowledge-based development of new catalysts, a number of characterization methods require cm-large and well-defined single crystalline samples. For example as catalysis takes place at the surface, it is important to investigate the surface structure and surface terminations for different crystallographic orientations. For this purpose it is necessary to grow cm³-size single crystals of InPd, although of course in possible future applications fine powder or even nanoparticles will be used as for effective catalysts high specific surfaces are needed.

The Czochralski technique was applied to grow InPd crystals from In-rich solutions instead of growth from a congruent melt (melting point: 1285°C [3]) to reduce the relatively high vapour pressure of indium. The main problem of incorporation of In-rich solution droplets during growth could be solved by applying very low pulling rates in the range of 100 μm/h or even less and adjusting other experimental parameters.

We will present our Czochralski growth setup as well as the experimental conditions to get single-phase crystals and will discuss the results of the characterization of the grown crystals.

[1] M. Armbrüster et al., J. Am. Chem. Soc. 132 (2010), 14745.
[2] W.M.H. Sachtler, Catal. Rev. Sci. Eng. 14 (1976), 193.
[3] H. Okamoto, J. Phase Equilib. 24 (2003), 481.

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1. Czochralski crystal growth of intermetallic compounds from high-temperature solutions
2. Achievement and advancement in the hetero-epitaxial growth of AlN single crystals on SiC substrates by PVT approach
3. Czochralski single crystal growth in the Ga-Pd system