Quartz is one of the most common minerals in nature, and is the main mineral component of crystal, agate, river sand, silica, etc. It is widely used in traditional industries such as glass, architecture, gem and stone decoration. Since the 1960s, emerging technologies such as computers, new materials, and new energy have put forward higher requirements for the purity of quartz products, and the concept of high-purity quartz has been born.
High purity quartz refers to the quartz and its products with very high purity of SiO2 and very low content of impurity elements. It is an indispensable and important functional material for semiconductor, photovoltaic, optical fiber, precision optics, lighting equipment, emerging glass and other industries. Strictly speaking, high purity quartz is not a mineral, but a product purified by crystal, gangue quartz, quartzite, granite pegmatite and other ores as raw materials, so it is more appropriate to call the deposit that can purify and produce high purity quartz as high purity quartz raw material ore.
Naturally formed high purity quartz is scarce or extremely limited (such as crystal), in order to obtain high purity quartz, it is often the natural high purity of quartz raw materials purified into high purity quartz. High purity quartz raw materials need to go through a series of purification processes to finally obtain high purity quartz sand products that meet the requirements of the application field. At present, the industrial types of mineral deposits that can be used as raw materials for high purity quartz are natural crystal, gangue quartz and granite pegmatitic quartz.
The world's high purity quartz raw material deposits are mainly distributed in the United States, Brazil, Canada, Australia, Russia, Mauritania, China, India, Norway and other 9 countries. The main ones are Spouspine and Boville deposits in the United States, the Drage and Nesorden deposits in Norway, the White Spring, Quartz Mountain, Sugar Bag Mountain, Lighthouse and Cresik deposits in Australia, the Kshtum and Salanpaul deposits in Russia, the John Bitz deposit in Canada, and the Chami and Um Aquinina deposits in Mauritania. Spruce Pine mine in the United States is recognized as a high quality quartz deposit in the world, which has the advantages of large scale, less fluid impurities and stable ore quality.
The purification potential of high purity quartz raw material is affected by the chemical composition, mineral composition, distribution size and consolidation degree of the ore. The mineralogy study of quartz raw material using various detection techniques is a key step to select the correct high purity quartz raw material. The research on high purity quartz raw materials should include at least three aspects: (1) the characteristics of quartz and gangue mineral intercalation, the content of mineral inclusions in quartz minerals is one of the factors that determine the total amount of impurity elements in the final high purity quartz; (2) Fluid inclusions, even if the quartz with a very low content of impurity elements is not necessarily high-purity quartz, when quartz minerals contain a large number of fluid inclusions, the SiO2 content is difficult to meet the technical requirements of high-purity quartz; (3) Lattice impurities, due to the extremely low content of lattice impurities but extremely difficult to remove, is the most critical factor restricting the quality of high-purity quartz.
High purity quartz is a product obtained from natural quartz raw materials after certain processing and purification. At present, there is no unified standard for the definition of high purity quartz.
Zhang Peicong et al. defined high-purity quartz as an aluminum lattice formed by aluminum-silicon isomorphic finite isotropy substitution in quartz lattice, with placeholder impurity content (lattice Al) ≤30μg/g, while other impurities (Ti, K, Na, Ca, Mg, Fe, etc.) synthesized ≤20μg/g of natural minerals. The corresponding quartz w(SiO2) purity ≥99.99% (4N).
The Norwegian Geological Survey proposed that under the premise that the total impurity content in high purity quartz is less than 50×10-6, the Al content should be less than 30×10-6, the Ti content is less than 10×10-6, the Na and K contents are less than 8×10-6, the Li and Ca contents are less than 5×10-6, and the Fe content is less than 3×10-6. P content is less than 2×10-6, B content is less than 1×10-6.
Wang Ling et al proposed that the general concept of high-purity quartz is quartz with w(SiO2)≥3~5N and w(Fe2O3) less than 10×10-6. According to SiO2 purity and high purity quartz products are divided into four grades: low-end w(SiO2)≥99.9%(3N), mid-end w(SiO2)≥99.99%(4N), high-end w(SiO2)≥99.995%(4N5), high-end w(SiO2)≥99.998%(4N8). According to the total amount of impurity elements such as Al, B, Li, K, Na, Ca, Mg, Ti, Fe, Mn, Cu, Cr, Ni in the product: low-end products ≤1000×10-6; Mid-end product ≤100×10-6; Medium and high-end products ≤50×10-6; High-end products ≤20×10-6.
Worldwide, the main manufacturers of high purity quartz sand are United States Unimine, Norway TQC, China Quartz shares and so on. The quality index of the IOTA series of high purity quartz high-end products has become a recognized international standard.
Quartz industry chain with SiO2 as the main raw material made of quartz products, of which, high purity quartz sand is mainly used in the production of natural quartz glass, widely used in semiconductor, aerospace and other high-end manufacturing industries, with high added value.
Quartz products have a series of excellent physical and chemical properties, including very low thermal expansion coefficient, excellent high temperature resistance, good chemical stability, excellent electrical insulation, low and stable ultrasonic delay, the best ultraviolet, visible light and near-infrared spectral transmittance, higher than the mechanical properties of ordinary glass, etc. Can produce quartz ingot, pipe, bar, plate, crucible, utensils and devices, quartz fiber and fabric and other products.
In the semiconductor field, there are many kinds of semiconductor quartz products, mainly used for silicon wafer manufacturing single crystal quartz crucible, silicon wafer bearer, photomask substrate materials, etc., are the key auxiliary materials in the semiconductor production process. Single crystal growth requires the use of quartz crucible and quartz devices, wafer processing part of the etching, diffusion, oxidation, annealing and other steps need to use a large number of auxiliary quartz glass, such as quartz sheets, quartz rings, quartz boats and other high-purity quartz products.
In the photovoltaic industry, quartz crucible is an indispensable support material for the photovoltaic industry, is an important supporting key consumables for the production of silicon materials, which can support solar users to continuously draw large-diameter monocrystalline silicon under high temperature conditions, which is used to contain molten silicon and make crystal rods required for subsequent processes.
In the field of optical fiber communication, high-purity quartz glass products are important materials in the optical fiber production process, and are widely used in the optical fiber prefabrication rod and optical fiber wire drawing process.
In the field of optics and light sources, quartz products of electric light sources can be used to produce ultraviolet tubes, high-purity quartz tubes, transparent tube lamps, which are widely used in lighting and special light sources industry. High purity quartz glass is used in the production of telescope lenses and laboratory optics, communication equipment, diffraction lenses, projection displays, scanning equipment and printers for optics, lasers, as well as camera and hyperflat TV screens, flame control equipment, etc.
At present, the international high-purity quartz products enterprises mainly include Dongcao, Heraeus, Covalent, Shin-Yue, Kunxi, etc., among which the semiconductor quartz crucible is mainly monopolized by Heraeus, Shin-yue, Maitou and other enterprises. China's main high-purity quartz products manufacturers are quartz shares, Feilihua, Cade quartz and so on.
