Structural-diffraction analysis of nanocrystalline materials

We have studied the structure and phases of boron nitride and zirconium dioxide (both have a wide spectrum of crystalline sizes) using x-ray analysis and electron diffraction microscopy. We show that, even when the crystallites are of order 100 nm, their diffraction pattern is similar to that of other nanocrystalline materials. This pattern is dictated by the high degree of dispersion and the lattice distortions of the crystallites' periphery. The distortions in these materials are caused by internal stresses. In boron nitride the stress relaxes by polygonization of the peripheral regions. This destroys the long-range translational order and leads to the formation of intercrystallite regions due to incoherent binding between crystals. In zirconium oxide short-range order is destroyed by variations in the lattice constants in the regions near the crystal faces.