Abstract: A method and an apparatus for purification of metallurgical grade silicon by directional solidification and for obtaining silicon ingots for photovoltaic use. The method comprises a preheating step, up to a temperature that is higher than the melting point of silicon, of a quartz crucible (18) that is accommodated in a containment enclosure (19) arranged inside a chamber (4) of a furnace. The chamber (4) of the furnace is delimited by a covering structure (3) and by a footing (2), which can move with respect to each other, or vice versa, toward or away from each other along a vertical direction respectively for opening and closing the chamber (4). Heating occurs by way of heating means (10) of the electric type, which are associated with the walls of the covering structure (3).

Abstract: A method for preparing silicon for photovoltaic use starting from metallurgical-grade silicon, comprising the following steps, performed by means of devices made of materials suitable to prevent silicon contamination: providing a silica powder and a carbon black having a reduced content of boron, phosphorus and metallic impurities and a binding agent; preparing a mixture of silica powder, carbon black and binding agent and preparing pellets with the mixture; subjecting the pellets to a first thermal treatment; subjecting the heat-treated pellets to carbon reduction, so as to obtain silicon in the molten state; subjecting the silicon in the molten state to a first purification; subjecting to directional solidification the silicon in the molten state in a directional solidification furnace, so as to obtain silicon for photovoltaic use.

Abstract: An X-ray intensifying screen comprises a support and a layer containing a direct emission phosphor formed without a binder. The preferred direct emission phosphor is a rare earth silicate phosphor. Said X-ray intensifying screen is useful in the methods for recording and reproducing high energy radiation images. A process for the preparation of the binderless phosphor layer by reactive spray pyrolysis is also disclosed.

Abstract: A process is disclosed for purifying silicon wherein silicon in the molten state is reacted with barium carbonate and/or oxide and/or hydroxide and then, after cooling and crushing, leached with one or more dilute inorganic acids. Preferably an oxidizing gas such as oxygen or water vapor is blown into the molten mass during the reaction, which is conducted at a temperature in the range of from 1550.degree. to 2000.degree. C. The inorganic acid may be for example hydrochloric acid, hydrofluoric acid, nitric acid, sulphuric acid, or mixtures thereof.