A Surface-Layer Texture Model for Correction of the Preferred-Orientation Effect

A model where texture is supposed to concentrate in a surface layer of the sample is presented and tested by measurement of X-ray intensities from ammonium chloride powder samples. The orientation distribution of the rotating sample is represented by the expansion of the symmetrized harmonics. The parameters of the model are adjusted by fitting of the calculated intensities with the experimental data. The intensity variation (radial pole figures) of six reflections from four samples of different density are measured and fitted with the model. The results show that the surface-layer model describes well the texture of the samples. The experiments also outline some particular features of the orientation distribution of a powder sample.