By the early 1990s, the proven indium reserves in the United States were about 1 1,000 tons, while those in Peru, Sweden, South Africa and Canada were all several thousand tons (China Institute of Geology and Mineral Information, 1 1,993).
Indium resources are mainly produced in Peru, Bolivia, Canada, Russia, China, France, Belgium, Britain, the United States and Japan, and most indium-rich deposits are produced in the Pacific Rim. Mount plesent tin polymetallic deposit has thousands of tons of indium. After 1998 is put into production, the annual output is 25 tons of indium and 3500 tons of tin. Indium-rich deposits in Russia are produced in the Far East. The United States and Japan are big consumers of indium in the world and attach great importance to indium resources. For more than 20 years, they have been paying attention to the exploration and protection of indium resources, and have successively discovered many indium-rich deposits, such as Kagoshima, Miaomu, Yufeng, Fengyuan and Zhonggu in Japan, all of which are famous indium-rich deposits in Japan. The potential resources of indium in China are quite rich. Indium-rich deposits have been discovered in 16 provinces, with proven indium reserves of nearly 20,000 tons and prospective indium reserves of over 65,438+10,000 tons. More than 80% of the reserves are distributed in Guangxi, Yunnan, Inner Mongolia and Guangdong provinces (among the 25 indium-rich deposits in the four provinces, there are 2 large and medium-sized indium-rich deposits/kloc-0 and 3 small ones). It accounts for more than 80% of indium reserves in China. Among them, Guangxi and Yunnan rank first. The indium reserves of Dachang ore field in the west of Nanling alone are more than 6,000 tons, the Dulong tin-zinc deposit is more than 4,000 tons, and the Gejiu tin deposit is more than 2,000 tons. The Bainiuchang tin polymetallic deposit in the same area is also a super-large indium-rich deposit. The research shows that the tin-lead-zinc-silver polymetallic deposits in eastern Inner Mongolia, such as Meng 'en Tolgoi, Dajing, Budunhua, Baiyinnuo, Nao Niu Shan and Aonaodaba, also contain high indium. Meng 'en Tolgoi deposit has more than 400 tons of indium reserves, which may become another important indium-rich deposit concentration area in China.
In the past, people thought that indium was mainly recovered from lead-zinc deposits. In fact, not all lead-zinc mines are rich in indium. One of the important reasons is the scarcity of indium resources, so the recovery index of indium in lead-zinc ores is set very low (5× 10-6 ~ 10-6, Office of the State Mineral Reserves Committee, 1987. By indium-rich deposit, we mean a deposit rich in indium. In general, the indium content in ores is above (50 ~ 100) × 10-6, and sphalerite (the main metal mineral containing indium) is (500 ~ 3000) × 10-6, or even higher.
Indonesia, Malaysia and other Pacific Rim countries produce world-famous cassiterite sulfide deposits. However, due to the lag of industrial discovery, the research and development of indium in these countries is relatively weak. It is considered that indium in these areas has great potential for developing and utilizing resources.
Second, the application and demand of indium
From the discovery of indium to nearly 100 years ago, the research and utilization of indium was as scarce as its quantity, and people's attention to indium kept pace with the development of world industry. With the rapid development of industry, in addition to traditional fields such as semiconductor, radio, solder, adhesive, sealing alloy and electromechanical alloy, the application of indium is also developing rapidly. At present, indium has been widely used in the fields of new semiconductor alloys, solar cells, optical fiber communication, atomic energy, aerospace technology, computers, television and anti-corrosion, and new technologies and new uses are constantly being developed.
With the rapid expansion of indium application, the world indium output is also rising linearly. 1924 The world indium output is only 1kg. By 1980, the indium output reached 45.5t, 1990 133t, 1995. China is not only a big country in indium resources, but also a big country in indium production. Indium was recovered from polymetallic ore from 1954 to 1990, and the output reached 1 1t,1997,48t, 198. The domestic indium consumption is less than 2t, and the deep processing capacity is very weak. With the increase of output and the influence of quick success and instant benefit, China has become a big exporter of indium, with 198 23.737 t, 199 4 1.92 t and 50 t in 2000, which made the international price of metallic indium drop sharply from nearly 400,000 USD /t in the early 1990s to 600,000 yuan /t in the early 2000. The cheap export of this precious strategic metals has triggered a large accumulation of indium in industrialized countries.
Due to the special physical properties of indium, its application scope is expanding rapidly, especially in the past 10 years, with the development of many new technologies and new fields, the demand for indium is increasing day by day. To sum up, at present indium is mainly used in the following aspects:
(1) In the field of low-melting-point indium alloy materials, indium low-melting-point alloys have good mechanical properties, corrosion resistance and high conductivity, and are often used as low-resistance contact materials and low-pressure cold fluxes. Binary or ternary low melting point alloys of indium have higher high-temperature tensile strength and fatigue strength, and indium alloy solders are more advanced than lead-tin and Suk Kim solders. Due to the good ductility of indium material at low temperature, the reliability of landing is greatly enhanced when it is used in the lunar module, and it is not brittle or cracked. At present, there are more and more kinds of indium alloys.
(2) In the field of semiconductor, indium is the earliest and most widely used in the field of semiconductor, which can be used as dopant, contact agent and solder for semiconductor germanium, transistors and electron tubes. Indium is often used to produce semiconductor materials, such as indium antimonide, indium phosphide and indium arsenide. Indium antimonide is the earliest research and application, and indium phosphide is the most promising at present, which shows gratifying prospects in communication laser light sources, solar cells and so on. Indium antimonide and indium arsenide are mainly used in infrared detection, magneto-optical devices and solar converters.
(3) Se-In-Cu polycrystalline thin film solar cell This technology was successfully developed in 1980s, and it has the characteristics of high thermal conversion rate, low cost, superior performance and simple production process.
(4) In the field of atomic energy, indium can sensitively sense neutron radiation, so the amount of materials used for monitoring in the atomic energy industry is as large as that in the electronic industry.
(5) In the field of anti-corrosion, indium has good anti-corrosion performance, which was discovered by Mitsui Metal Mining Company of Japan when it was studying to reduce the amount of mercury in preservatives. Now all battery manufacturers in Japan have completely solved the corrosion problem with indium. The corrosion of zinc powder used in the battery produces hydrogen, which reduces the performance and life of the battery. Mercury, originally used for anti-corrosion, has produced uncontrollable environmental pollution. 1984 Japan began to study indium instead of mercury. 1992 batteries were mercury-free, which opened up new uses of indium. According to the data of Liu (200 1), in this new application, the amount of indium added is 100× 10-6, and in this application, the indium consumed by Japan is 2 t, 1993 and1993 respectively.
(6) Indium phosphide used in optical fiber communication market has been used in the field of optical fiber communication, mainly as a substrate for producing semiconductor indium gallium arsenic phosphide to improve the performance and stability of optical fiber.
(7) TV picture tube electron gun In the production of picture tube electron gun, indium is used instead of scandium, which on the one hand reduces the cost, and at the same time is beneficial to high power output and prolongs the service life.
(8) Application of indium tin oxide (ITO) Visible light transmittance of ITO >: 95%, ultraviolet absorption rate > 70%, microwave attenuation rate >; 85%, with good electrical conductivity and processability, wear resistance and chemical corrosion resistance, so it is widely used.
ITO is the largest market for indium consumption at present. Japan is the world's largest consumer of indium, accounting for more than 70% of the world's indium consumption. The figure of 1995 shows that Japan consumed 92t of indium that year, of which 52t was used for ITO. ITO is mainly used to produce thin film transistors (TFT), liquid crystal displays (LCD) and plasma displays. The cathode ray tube of traditional CRT display also needs a considerable amount of indium, and there is no substitute for ITO in this application.
Indium has many other uses. For example, due to its strong corrosion resistance and strong light reflection ability, indium can be used to make mirrors for ships, which can not only keep bright for a long time, but also resist the erosion of seawater; Using the low melting point of indium, a special alloy is made, which is used for circuit breaker protection device and automatic control device of fire fighting system. In addition, indium is also used as anti-corrosion decorative materials for wear-resistant bearings, dental alloys, steel and non-ferrous metals, and traditional jewelry. ITO is also used as defogging agent and defrosting agent for building glass and automobile glass.
Before 2000, the world demand for indium increased by 4% ~ 5% every year, and from 2000 to 200 1 year, the growth rate reached 10% ~ 15%. It is estimated that in the next few years, with the further popularization of personal computers, especially in the near future, the demand for indium will increase rapidly. Therefore, doing a good job in the exploration and research of indium resources, strengthening the research of indium application technology and storing indium are the keys to ensure the near-term combat readiness.
Thirdly, the research status of indium resources is summarized.
Scholars all over the world have studied indium for more than half a century and made great contributions in two fields. One is the geochemical properties of indium, the content of indium in various rocks, minerals and meteorites on the earth, and indium-rich ores. A large number of indium deposits have been discovered all over the world. The second is the application of indium. At present, indium is widely used in new fields such as radio, aerospace technology and the development of high-performance alloy materials, and the demand for indium is increasing, which in turn promotes the research of indium resources. Therefore, from the 1950s to the present, the research on indium mineralization in some developed countries has never stopped, and great progress has been made, and there is a tendency to pay more and more attention to it.
A great deal of research on indium began in 1950s. The researchers in this period are mainly western scholars, and the research focus is on the geochemical properties of indium (Shaw, 1952,1957; Fleischer et al., 1955), thermodynamic study of In-In3S2 (Thompson et al., 1954), indium in intrusive rocks and minerals (Wager et al., 1958) and trace elements including indium in sulfides (Fleischer).
In 1960s and 1970s, Soviet scholars pushed the research of indium to a climax. They studied the distribution of indium in different rocks and deposits in the former Soviet Union in detail, found a number of indium-rich deposits and put forward the concept of "geochemical star" in indium geochemistry (иванов, 198). It is found that the higher the tin content in the ore, the higher the indium content in the sulfide, and the enrichment of indium is related to the high temperature metallogenic conditions. The study of indium in rocks and deposits of different ages shows that the indium content has increased from old to new; Published the book "Dispersed Element Deposits" (Ivanov et al.,1977); Many scholars combine indium with other dispersed elements and main ore-forming elements such as Zn and Fe to discuss the genesis and comprehensive utilization of the deposit, and think that in in sulfide deposits indicates the genesis of the deposit and has industrial comprehensive utilization value (Beus et al.,1960; Ganeev et al.,1961; Иванов, 1966; Ivanov,1968; Shtereberg et al., 1967). Scholars from other western countries have also done a lot of research work during this period, such as Boorman et al. (1967) on indium in Mount plesent tin mine, and Caley et al. (1967) on indium in western Mexico. Chakrabarti( 1967) relates trace elements in sulfide deposits to mineralization.
In the 1980s and 1990s, Soviet scholars continued to strengthen their research on indium, and subsequently discovered some indium-rich deposits (Gonefchuk, 199 1). Greta (1980) has a unique research on indium in seven Bulgarian coal mines. It is found that the indium content in coal is very high, some coal samples contain indium (20 ~ 167) × 10-6, and some coal samples contain indium more than 1000 × 10. Indium deposits or indium ore bodies (Johan,1988; Marao et al.,1992; Kieft et al., 1990). During this period, Japanese scholars have made great progress in the study of indium-rich deposits, and indium ore bodies and deposits have been discovered in Nursery, Kagoshima, Fengyuan, Zhonggu and other places, making Japan's indium resources leap to the forefront of the world (Murakami et al.,1990; Satoshi Murao et al.,1991; Marao et al.,1992; Ota Hideyoshi,1993; Tsushima et al., 1999), sphalerite and sulfide minerals containing Cu-Fe-Zn-Sn-S in Zhonggusi deposit contain indium 1.8% ~ 16.3%, and the ore contains indium 0.02%, which constitutes a typical indium deposit (Tsushima et al., 650) At the same time, foreign scholars have obviously strengthened their research on indium mineralization, including the study on the existing forms of indium (Johan, 1988), the experimental study on the synthesis of indium-bearing minerals (Raudsepp et al., 1987), and the study on the relationship between indium and tin in basalt, sulfide and mantle (literature and art, etc., 1995). With the deepening of research, some new indium minerals have been discovered. Up to 1980, five kinds of indium minerals have been discovered in the world, three kinds of indium minerals have been discovered in recent 20 years, and there are still three unnamed indium minerals, which increases the number of indium minerals to 1 1.
In 1970s, China scholars did little research on indium before, and only saw a few documents with a small amount of indium information. Later, it was proved that there were some problems in the reliability of indium content. Since 1980s, the research on indium in China has been increasing day by day, but the main research object is tin-copper-lead-zinc sulfide deposits, and the research method is mainly the comprehensive study of various trace elements in ores. Although every scholar wants to explore the comprehensive utilization value of indium, he has not specifically studied the mechanism of indium enrichment and mineralization, nor has he studied indium as a mineral. During this period, Tu Guangchi and others (1984) studied more than 30 stratabound lead-zinc deposits in China, Tong (1984) studied more than 10 lead-zinc deposits in Hunan, and foreign countries such as Pankratyev and others (198 1) studied them in Uzbekistan. Ye Qingtong (1982) studied the sphalerite composition in Yinshan, Fankou, Dongpo and Taolin deposits, and Song (1984) studied the trace elements in Fankou lead-zinc deposit in Guangdong, showing the content characteristics of indium and other trace elements in some lead-zinc deposits in China. Tu Guangchi et al. (1993) systematically summarized and discussed the content characteristics of indium in almost all types of lead-zinc deposits in China, as well as the distribution characteristics of trace elements such as indium in skarn sphalerite and magmatic hydrothermal lead-zinc deposits except syngenetic deposits and reformed deposits. Zhang et al. (198 1), et al. (198 1) and et al. (1988) made a comprehensive study on the dispersed elements in Guangxi Dachang mine field, and pointed out that indium in Dachang mine field is one of the valuable dispersed elements. Zhang Qian (1987) investigated trace elements in more than 60 lead-zinc deposits at home and abroad, and found that except for some tin-bearing lead-zinc deposits, the indium content in tin-free deposits is very low, and most lead-zinc deposits with transformation origin and syngenetic sedimentation origin have almost no industrial use value. At the same time, some characteristics of dispersed elements including indium are directly related to the genesis of the deposit, and the map drawn shows the trace patterns of almost all lead-zinc deposits. Liu Yingjun et al. (1984) studied the geochemistry of indium, and affirmed that indium entered sulfide in tetrahedral lattice coordination during the precipitation stage of hydrothermal process, and sphalerite with this lattice coordination was the best mineral to enrich indium. The mechanism of indium entering sphalerite in large quantities was clarified from the aspect of crystal structure. However, judging from the phenomenon that sphalerite in most lead-zinc deposits is not rich in indium, it is conditional for indium to enter sphalerite.
China Institute of Geology and Mineral Information (1993) clearly put forward the concept of indium deposit in the book Minerals of China. Academician Tu Guangchi clearly put forward the theory that dispersed elements can form ore deposits. With the increasing demand for indium in China in the future, the research and utilization of indium resources have attracted people's attention, and some problems of indium-rich integrated mines have also been preliminarily understood.