Si-TaSi2 in situ composites: a new monochromator material for hard X-rays

The Si matrix of two Si-TaSi2 in situ composites grown in the 111 direction have been characterized by means of triple axis diffractometry using synchrotron radiation with photon energies of 120 and 160 keV. The Si matrix is compressed in the growth direction and dilated along two orthogonal directions perpendicular to it. The rocking curves show no grains or peaksplitting over a large area of the sample, and their full width half maximum is of the order of similar 0.03 . The integrated reflecting power in this energy range is about 400 times larger than the theoretical value for perfect Si crystals. These properties make Si-TaSi2 composites an interesting monochromator material for diffraction experiments with hard X-rays when intermediate resolution is required. In addition to the properties of the Si matrix, diffraction from the TaSi2 rods has been studied. They are highly oriented crystals and cause strongly anisotropic deformation in the Si matrix, which opens the possibility of varying the k-space resolution of the diffractometer merely by tilting the monochromator, and, in the case of a triple crystal diffractometer, by tilting the analyzer crystal as well. (orig.)