QUARTZ RAW MATERIALS OF LOWER BAVARIA – SILICON FOR SOLAR CELL TECHNOLOGY

Silicon is one of the most important materials in our time. Cleaned by means of different procedures it is used in metallurgy (metallurgical grade silicon), in photovoltaics (solar grade silicon) and in microelectronics (electronic grade silicon).

Metallurgical grade silicon (98-99 % SiO₂) is needed for producing silanes, siloxanes and silicones as well as for manufacturing aluminium-silicon alloys. In addition, poly-crystalline ultra pure silicon (99.99 % SiO₂) for solar cell production and mono-crystalline ultra pure silicon (99.9999999 % SiO₂) as the basic material for microelectronics are made from metallurgical grade silicon, which was purified in several processes.

In Germany metallurgical grade silicon is currently only manufactured in Pocking (Lower Bavaria)

Metallurgical grade silicon is produced by quartz gravels and pieces of vein quartz reacted with reduction materials such as coal, coke and charcoal at temperatures of about 2000 °C in electric arc furnaces. The quartz gravel and the vein quartz need a minimum grain size of 16 mm and a maximum grain size of 80 mm and have to meet the following criteria (in percent): SiO₂ > 99.6, TiO₂ < 0.008, Fe₂O₃ < 0.05, Al₂O₃ <0.1- 0.2.

Apart from vein quartz of the Bavarian “Pfahl", high purity tertiary quartz gravels, which can only be exploited in a few locations in Lower Bavaria, are used as raw materials.

Because of the increasing use of renewable energy sources, the search for quartz raw materials is an important task for the department “Economic Geology” of the Bavarian Environment Agency.

To prevent an impending shortage of raw materials, quartz deposits in different tertiary gravels have therefore been explored since 2006, especially in the East of Lower Bavaria, with a total of 36 bore holes.

15 bore holes are in the area of the so-called “Haarschedler Schotter”, 4 bore holes in the region of the “Ortenburger Schotter” and 17 bore holes in the field of the “Quarzrestschotter”.

To date, a total of 4 areas with quartz gravel deposits, which are interesting for the silicon industry, are bordered. For one of these occurrences the quartz gravel industry has already made appropriate plans of mining.