TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The silica powder containing (ppm by weight) vanadium (V) (1-5), iron (Fe) (0.1-5), chromium (Cr) (0.01-0.02), titanium (Ti) (0.8-3.5), copper (Cu) (0.05-0.5), aluminum (Al) (1.5-16), calcium (Ca) (1-5), magnesium (Mg) (0.1-1.5), boron (B) ( less than or equal to 0.1), and phosphorus (P) ( less than or equal to 0.1). The carbon black has no polycyclic aromatic hydrocarbons (PAH) and containing (ppm by weight) V (1-5), Fe (0.5-1.5), Cr (1.6), Ti (0.05-2), nickel (Ni) ( less than or equal to 0.4), B (0.05-2), and P (0.05-0.1). The binding agent is saccharose. The graphite contains (ppm by weight) V (5.1-5.8), Fe ( less than or equal to 0.08), Cr ( less than or equal to 0.02), Ti (0.3), Ni (0.2), Al (0.02-0.04), B (0.05) and P ( less than or equal to 0.02). Preferred Method: The method (M1) involves selecting silica powder having content of (ppm by weight) vanadium (V) (1-5), iron (Fe) (0.1-5), chromium (Cr) (0.01-0.02), titanium (Ti) (0.8-3.5), copper (Cu) (0.05-0.5), aluminum (Al) (1.5-16), calcium (Ca) (1-5), magnesium (Mg) (0.1-1.5), boron (B) ( less than or equal to 0.1), and phosphorus (P) ( less than or equal to 0.1); carbon black without PAH having content (ppm by weight) of V (1-5), Fe (0.5-1.5), Cr (1.6), Ti (0.05-2), nickel (Ni) ( less than or equal to 0.4), B (0.05-0.1), and P (0.05-0.1); and binding agent selected from saccharose, starch, cellulose, polyvinyl alcohol and NaSiO3; preparing mixture of the silica powder, carbon black and binding agent; preparing pellets of the mixture; subjecting the pellets to first thermal treatment in tunnel furnace heated with indirect hot air to temperature comprised 150-250 degrees C for time comprised between 20 minutes and one hour; treating the pellets subjected to the first thermal treatment in a 2-MW submerged arc furnace which comprises three graphite electrodes that have content of Fe of less than or equal to 10 ppm by weight; internal surface of silico-aluminous bricks containing silica in quantity 65-95 wt.% at the top; crucible made with high-purity graphite hearth with Fe content of less than or equal to 10 ppm by weight and annular element of high-purity graphite which has Fe content of less than or equal to 10 ppm by weight, operating the furnace with current, at the electrodes comprised 8-12 KA and voltage comprised 60-140 V, so as to obtain silicon in the molten state; subjecting the silicon in the molten state to procedure for nucleation and growth of silicon carbide (SiC) crystals in ladle, the ladle having lining made of material containing silica in quantity 80-95% and less than or equal to 50 ppm of Fe and inner surface constituted by quartz having B content of less than or equal to 0.1 ppm by weight, so as to form SiC crystals; transferring through filter the silicon in the molten state within which the SiC crystals have formed into quartz crucible lined with silicon nitride, the crucible is accommodated in container made of ceramic material based on alumina or silico-aluminates or silicon carbide, the crucible is arranged within furnace for directional solidification, which is preheated to temperature above 1450 degrees C, so as to remove the SiC crystals; keeping the silicon in the molten state transferred into the quartz crucible within the furnace for directional solidification at temperature 1420-1470 degrees C for time 1-2 hours; subjecting to directional solidification the silicon in the liquid state transferred into the quartz crucible within the furnace for directional solidification by progressive removal of heat from the bottom of the quartz crucible at rate 2-10 cm/hour in inert atmosphere, so as to obtain silicon for photovoltaic use. The silica powder, carbon black and binding agent, before is mixed, are kept, in steel tanks lined with material selected from polyvinylidene fluoride and polyethylene. The mixing of the silica powder, of the carbon black and of the binding agent occurs by units of mixing device that is lined with material selected from polyvinylidene fluoride and polyethylene. The preparation of the pellets occurs by units of compaction device that is lined with material selected from polyvinylidene fluoride and polyethylene.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Apparatus: The furnace for directional solidification is apparatus comprises furnace that comprises footing and covering structure which delimit chamber, the former is able to move with respect to the latter or vice versa toward and away from each other along vertical direction respectively for opening and closing the chamber; heating units of the electrical type, which are associated with the walls of the covering structure and are associated with control units, suitable to activate them on command and to modulate the power delivered by them; at least one quartz crucible, which is accommodated in containment enclosure that rests on the footing; at least one opening which is formed in the ceiling of the covering structure and with which closure element of the removable type is associated; units for dispensing at least one inert gas, which are arranged proximate to the opening and are suitable to generate on command barrier of the inert gas that covers at least the area of the opening, when the chamber is closed, the covering structure and the footing is moved mutually close, and the closure element is removed, for transfer through the opening of silicon in the molten state directly into the quartz crucible; at least one heat exchange plate, which is cooled by circuit of refrigerant fluid and is associated with the footing, for the removal of heat from the bottom of the quartz crucible; units for feeding inert gas inside the chamber when closed, the covering structure and the footing is moved mutually close, in order to generate inside the closed chamber inert gas atmosphere at pressure that is higher than atmospheric pressure. EXAMPLE - No suitable example given.