Cristaux à gradient de maille

Abstract

This paper reports original results on a range of single crystals having a continuous lattice parameter variations. The main aim of these investigations is to replace conventional neutron monochromators by high perfection single crystals having a gradient in the lattice spacing. This is because it has been shown that such a type of crystal would considerably improve the neutron physics techniques. In order to obtain such crystals, the general idea followed in this work is to continuously change the relative concentration of a two-component single crystal solid solution by a suitable growing process.The first experiments have been carried out on a CoONiO monocrystalline solid solution grown by the fame fusion process. Alkali halides have also been investigated using the KClKBr solid solution. Single crystals have been grown in a Bridgman crucible by the zone melting technique.Finally using a special growth method, attention was focused on CuGe solid solutions; these are of special interest in neutron diffraction. The Ge concentration was varied from ≅2% to ≅10%, with a corresponding total relative variation of the lattice spacing of Δdd ≅ 1%. The mosaic spread of the crystal (dimensions, h = 4 cm, diam. = 1 cm) was found to lie between 35 and 120. The measurements were carried out by X-ray, γ-ray, neutron diffraction techniques and electron micro-analyser.