Abstract: The present invention relates to silicon with a high oxygen content and, at the same time, a high density of crystal lattice dislocations, and to its production. This silicon may be used in photovoltaics. Solar cells which are based on the material according to the invention exhibit high levels of efficiency despite the high oxygen content.

Abstract: Low-silking iron oxide yellow pigments having improved color qualities are produced by a novel method which utilizes both precipitation process and the Penniman process. Pigments are nucleated and grown by precipitation to achieve multiplication factor of 2.5 to 7 and additional pigment growth is carried out by the Penniman process.

Abstract: Novel rutile mixed phase pigment microgranulates are disclosed which comprise hemispherical particles indented to form toroid-shaped beads. The microgranulates are free-flowing, non-dust forming, and are stable in handling.

Abstract: Red iron oxide pigments having a lower metal impurity content and enhanced purity of color are disclosed as being comprised of clusters of spherical particles.

Abstract: Chromium oxide green in the form of donut-shaped, ring-shaped or tire-shaped particles having an internal diameter of from 0.01 to 0.5 mm and an external diameter of from 0.05 to 1.0 mm is prepared by spraying an aqueous chromium oxide green suspension through a liquid pressure nozzle into a spray dryer such that the suspension entering the drying space of the spray dryer is rotating.

Abstract: Chrome green oxide useful, inter alia, as a coloring material and having a water number of 10 to 40 g/100 g is prepared by adding sulphonic acid compounds, polyphosphoric acid compounds, polyacrylic acid compounds or mixtures thereof, in quantities of from 0.1 to 2% by weight, to an aqueous suspension of chrome oxide green pigment having a BET surface area of from 1 to 20 m.sup.2 /g before drying, and then drying the suspension.

Abstract: Iron oxide red pigments comprise clusters of a plurality of pigment particles, preferably at least five intergrown spherical particles, are prepared by conducting nuclear formation of iron oxide yellow .alpha.-FeOOH in the presence of compounds of the elements, B, Al, Ga, Si, Ge, Sn or mixtures thereof in quantities of from 0.05 to 10% by weight, calculated as tri- or tetravalent oxides and based on the arithmetically calculated precipitated .alpha.-FeOOH nuclei, separating brine from the resulting yellow slurry to isolate an iron oxide yellow paste, drying and annealing the paste to form iron oxide red pigment and grinding the red pigment, which pigment is useful in coloring foodstuffs, lacquers, plastics and building materials.