The defocusing of the diffracted beam in a texture goniometer using the reflexion technique for the determination of the preferred orientation is discussed. By means of textureless (random) specimens of the ferromagnetic material Ba3CozFez.,O4~ this defocusing is measured for several diffraction planes in two cases: (1) a narrow and (2) a wide receiving slit. Calibration functions to correct for defocusing effects are calculated using an equation given by Gale & Griffiths [ Brit. J. Appl. Phys. (1960). 11, 96-102]. The calculated functions plotted rersus the angle of specimen tilt are compared with the relative intensities measured on random specimens.

Samples of the ferrimagnetic material Ba3Co2Fe24041, pre-aligned in a magnetic field and sintered at various temperatures, have been examined for preferred orientation. Schulz's reflexion technique and the standardizing method of Holland were used to determine quantitative pole figures of several lattice planes. The texture bears a close resemblance to a 'fan texture' in which the crystallites have their basal planes parallel to a preferred direction. The sharpness of the texture increases with increasing sintering temperature. At 1320°C an exaggerated grain growth takes place. Inhomogeneity of the magnetic field throughout the sample results in local differences in orientation.243

Samples of the ferrimagnetic material Ba3Co2Fe24O41, prealigned in a rotating magnetic field and sintered at 1260°C, have been examined for (1) preferred orientation, (2) grain growth, and (3) porosity. The quantitative orientation of the fibre texture obtained in the samples measured by means of the (0001) pole figures, increases with sintering time. The maximum in the (0001) pole figures appears to be a linear function of the average intercept line length measured on sample surfaces perpendicular to the [0001] fibre axis. The relationship of texture and average intercept line length can be explained theoretically if it is assumed that the well oriented crystallites in the samples grow at the expense of the poorly oriented ones resulting in a decrease in number of the latter crystallites, whereas their averaged size remains unchanged. The transport mechanism of the densification process of the material used could not be determined. With the sintering equations given by Johnson [J. Amer. Ceram. Soc. (1970). 53, 574–577] the two transport mechanisms, viz. grain‐boundary and volume diffusion are possible. However, from the fact that the bulk porosity and the area pore fraction of the sample surfaces seem to be approximately proportional to the averaged intercept line length the conclusion may be drawn that the densification occurs most probably by volume diffusion.

Pellets of the ferrimagnetic material Ba3Co2Fe2.,Oa~ were sintered at temperatures between 1220-C and 1310"C in (1) a non-oriented state, (2) with a fibre texture generated by a rotating magnetic field during pressing and (3) with a fan texture due to a static magnetic field. During sintering up to 24 h. the changes in texture sharpness and density were studied. Textured samples attained a higher ultimate density than non-oriented ones and those with fibre texture became densest. To determine the sharpnesses of the texture the maximum standardized intensities of the reflexions 0,0,0,14, 1,0,1,16, 1,1,5,10 and 11_~0 were calculated from the experimental intensities. The mutual relations of the maximum standardized intensities of the four reflexions were given by representing the intensities of these reflexions for both textures as polynomials. The dependence of sharpness of texture on position in the pellet has been determined. It followed that this sharpness had to be averaged over the height of the pellet, to get a representative value for the whole pellet. Both kinds of texture were found to sharpen during normal grain growth, but during exaggerated grain growth in the last stage of sintering the sharpness of the fibre texture decreased, whereas that of the fan texture still increased. A possible explanation of this phenomenon is given on the basis of the different characters of these textures. A linear relationship is found between sharpness of texture and area porosity during normal grain growth. The compound starts decomposing at a lov~er temperature than that given in literature.