English is rare Rare Earth, which means "rare earth." In fact, this is nothing but a legacy to the people of the 18th century misunderstanding. 1787 people have been found after several kinds of rare earth elements, but the corresponding mineral rarely found. At that time, the level of science and technology limitations, one can only obtain some impure, like earth oxides like, so people will give this group of elements has left such an interesting and unique name.
According to the International Union of Pure and applied chemistry definition of rare earth elements, rare earth elements in Mendeleev's periodic table is the third sub-group from 57-71 atomic number of 15 lanthanide elements, namely lanthanum (57), cerium (58), praseodymium (59), neodymium (60), promethium (61), samarium (62), europium (63), gadolinium (64), terbium (65), dysprosium (66), holmium (67), erbium (68), thulium (69), ytterbium (70), lutetium (71), coupled with its electronic structure and chemical properties similar to scandium (21) and yttrium (39), a total of 17 elements. In addition to scandium and promethium, the remaining 15 elements often symbiotic.
According between physical and chemical properties of rare earth elements and some of the differences and geochemical properties of the separation process requirements, scholars tend to rare earth elements are divided into light and heavy groups or mild, moderate and severe groups. Two points system is bounded by gadolinium, gadolinium previous lanthanum, dysprosium, cerium, praseodymium, neodymium, promethium, samarium, europium seven light rare earth elements, also known as rare earth elements cerium group; gadolinium, terbium and gadolinium later, dysprosium, holmium, erbium, thulium, 9 element ytterbium, lutetium and yttrium called heavy rare earth elements, yttrium group known as rare earth elements. Although only 89 atomic weight of yttrium, but because of its ionic radius of the ionic radius of the other heavy rare earth elements into the chain link, which is closer to the chemical nature of the heavy rare earth elements. Symbiotic in nature but also with other heavy rare earth elements. Therefore, it is classified as heavy rare earth group. Light heavy rare earth three classifications not as obvious, such as sulfuric acid complex salt solubility according to the size of the rare earth can be divided into: Insoluble light rare earth cerium group that group, including lanthanum, cerium, praseodymium, neodymium, samarium; terbium group that is slightly soluble in RE group, including europium, gadolinium, terbium, dysprosium; easier insoluble yttrium group that heavy rare earth group, including yttrium, holmium, erbium, thulium, ytterbium, lutetium. However, the solubility differences between adjacent elements in between the groups is small, this method is not sub-net. Packets are multi-extraction, for example, two (2)-ethyl group (phosphoric acid) can be grouped among i.e. P204 neodymium / samarium, gadolinium, and then between the / terbium grouping. It had, lanthanum, cerium, praseodymium, neodymium called light rare earths, samarium, europium, gadolinium called the earth, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium plus yttrium-called heavy rare earths.
Rare earth content in the crust is not scarce, Clark value of this group of elements 0.0236%, which was 0.01592% cerium group elements, yttrium group elements 0.0077%; than common elements copper (0.01%), zinc (0.005%), tin (0.004%), lead (0.0016%), Ni (0.008%), cobalt (0.003%) so much. This group of elements but not the earth, but a set of typical metal elements, second only to its active alkali and alkaline earth metals.
Table 1-1 REE abundance in the earth's crust
Crustal abundance of the element name, ppm element names crustal abundance, ppm
Sc 25 Gd 6.1
Y 31 Tb 1.2
La 35 Dy 4.5
Ce 66 Ho 1.3
Pr 9.1 Er 1.3
Nd 40 Tm 0.5
Pm 4.5 * 10-1 Yb 3.1
Sm 7.06 Lu 0.8
Eu 2.1
REE position in the periodic table is very special, with 17 elements in the first ⅢB family, scandium, yttrium, lanthanum, respectively, for the fourth, fifth, sixth, long cycle in the first element of the transition elements of the series. 14 elements in nature is very similar to lanthanum after its chemists can only put them in a grid, no wonder some people regard them as "isotope" treatment, but because of their different atomic numbers, it can not be counted as real isotopes. That is, they are very similar nature, not exactly the same, which resulted in the separation of the difficulties of this group of elements, but also shows that as long as the use of its tiny difference, separation is possible; on the other hand, their electronic structure has a inner electron shell is not completely filled, ie 4f electron shell. 4f electrons due to the different layers, each element of this group of elements but also has a very special personality, especially optical and magnetic properties, like a plane full keyboard, wide range of piano.
Information, biotechnology, new materials, new energy, space and marine scientists are pushing for the six new contemporary science and technology base, why people attach importance to rare earth, rare earth research and development of rare earth, rare earth elements is to science and technology in these six groups have their to display their skills in the world. However, after all, a group of rare earth elements is not yet been fully recognized elements, which requires a great effort to study, understand them, and thus to hold grip them, so that they have a greater contribution to mankind.
Second, the common use of rare earth
Here we talk specifically about the timing of the application of various rare earth elements, in order to better distinguish light rare earths and heavy rare earths:
Lanthanum (La): lanthanum is widely used, as applied to a piezoelectric material, electric materials, thermoelectric materials, magnetoresistive materials, luminescent materials (blue powder), hydrogen storage materials, optical glass, laser materials, and various alloy materials . She also applied to the catalyst in many organic chemical products, light is also used to convert agricultural film lanthanum, in foreign countries, scientists lanthanum role conferred on crops "super calcium" reputation.
Cerium (Ce): 1, cerium as a glass additive can absorb ultraviolet and infrared, has been widely used in the automotive glass. Not only UV protection, can reduce the temperature inside the vehicle, thus saving air conditioning electricity. From 1997 onwards, the Japanese auto glass full join cerium oxide, cerium oxide for automotive glass in 1996 at least 2,000 tons, the United States about 1000 tons. 2, which is now applied to the cerium autocatalyst, you can effectively prevent a large number of car exhaust into the air in the United States consumption accounts for the total consumption of rare earths in this regard than a third. 3, cerium sulfide can replace lead, cadmium and other harmful to the environment and human metal applied to the pigments, coloring plastics can also be used, such as coatings, inks and paper industries. Currently leading the French company Rhone-Poulenc. 4, Ce: LiSAF laser system is the United States developed solid-state lasers, by monitoring the concentration of tryptophan can be used to probe biological weapons, but also for medicine. Cerium broad range of applications, almost all application areas contain rare earth cerium. Such as polishing powder, hydrogen storage materials, thermoelectric materials, cerium tungsten electrodes, ceramic capacitors, piezoelectric ceramics, silicon carbide abrasive cerium, fuel cell materials, gasoline catalysts, some permanent magnetic materials, all kinds of steel and non-ferrous metals.
Praseodymium (Pr): 1, praseodymium is widely used in building ceramics and ceramics for daily use, and it is mixed with glaze made of ceramic glaze, also available separately as underglaze paint, made of pale yellow pigment, color pure, elegant . 2, for the manufacture of permanent magnets. Selection of inexpensive neodymium praseodymium neodymium metal instead of pure metal magnetic materials, its antioxidant properties and mechanical performance has improved significantly, can be processed into various shapes of magnets. Widely used in all types of electronic devices and motors. 3, for the catalytic cracking of petroleum. Praseodymium, neodymium enrichment in the form of adding petroleum cracking catalyst zeolite Y, you can increase the activity, selectivity and stability of the catalyst. Beginning of the 1970s put into industrial use, the amount is increasing. 4, praseodymium can be used for abrasive polishing. In addition, the use of optical fiber in the field of praseodymium more widely.
Neodymium (Nd): the arrival of neodymium rare earth elements active in the field, play an important role in the field of rare earth, and about the rare earth market. Neodymium is the largest user of NdFeB permanent magnet materials. The advent of NdFeB permanent magnets, rare earth high-tech fields injected new vigor and vitality. NdFeB magnet high energy product, known as the contemporary "King of the permanent magnet of" its excellent performance is widely used in electronics, machinery and other industries. The successful development of the Alpha Magnetic Spectrometer, marking the magnetic energy of NdFeB magnets has entered the world-class level. Neodymium is also used in non-ferrous materials. Add the magnesium or aluminum alloy of 1.5 to 2.5% neodymium, the alloy can improve the high temperature performance, air tightness, and corrosion resistance, is widely used as aerospace materials. Further, neodymium-doped yttrium aluminum garnet laser beam generating a short, widely used in the industry thin material thickness of 10mm or less welding and cutting. In medical, neodymium-doped yttrium aluminum garnet laser instead of a scalpel is used to disinfect a wound or surgical removal. Neodymium is also used in glass and ceramic materials, coloring additives and rubber products. With the development of science and technology, expand and extend, neodymium rare earth elements in the field of science and technology will have a broader use of space.
Promethium (Pm): promethium for nuclear reactors produce artificial radioactive elements, the main purpose is as follows: 1, can be used as a heat source. Provide auxiliary power for vacuum detection and satellites. 2, Pm147 emit low energy β-rays, for the manufacture of a battery, promethium. As the missile guidance instruments, watches and clocks of power. Such a battery is small, can be used continuously for several years. In addition, promethium also for portable X- ray instrument, preparing phosphors, measure the thickness and beacon lights.
Samarium (Sm): samarium cobalt magnet is the first industrial application of rare earth magnets to get. This has SmCo5 permanent magnet system and Sm2Co17 series categories. The early 1970s, the invention of SmCo5 Department late invented Sm2Co17 department. Now based on the latter's demand-driven. Samarium-cobalt magnets of samarium oxide with a purity need not be too high, from the viewpoint of cost, the main use of the product is about 95%. In addition, samarium oxide catalysts is also used for ceramic capacitors and aspects. In addition, samarium also has nuclear properties of structural materials can be used as nuclear reactors, shielding materials and control materials to make nuclear fission to generate tremendous amounts of energy to ensure the safe use.
Europium (Eu): Europium oxide mostly for phosphors. Eu3 + for red phosphor activator, Eu2 + for the blue phosphor. Now Y2O2S: Eu3 + is the best luminous efficiency phosphor coating stability, recovery of costs. Coupled with the improved luminous efficiency and contrast improvements in technology, it is being widely used. In recent years, europium oxide is also used by stimulated new X-ray-emitting phosphor medical diagnostic systems. Europium oxide can also be used in the manufacture of colored lenses and optical filters for magnetic bubble storage devices in the control of nuclear reactor materials, shielding materials and structural materials can have a go. Long afterglow luminous powder production.
Gadolinium (Gd): 1, its water-soluble paramagnetic complexes in medical MRI can improve the body's (NMR) imaging signal. 2, which can be used as the sulfur oxides and a special x-ray brightness CRT screen grid matrix. 3, gadolinium in gadolinium gallium garnet magnetic bubble memory for storage is ideal for a single substrate. 4, in the absence of Camot circulation restrictions, can be used as a solid-state magnetic refrigeration media. 5, the level of the chain reaction inhibitor is used to control a nuclear power plant, in order to ensure the safety of the nuclear reaction. 6, is used as an additive samarium cobalt magnets to ensure performance does not change with temperature. Further, the use of gadolinium oxide and lanthanum together, and help to improve the thermal stability of the glass changes the glass area. Gadolinium oxide can also be used for manufacturing a capacitor, x-ray intensifying screens. In the world, efforts are being made to develop applications in magnetic refrigeration alloy of gadolinium and its terms, has been a breakthrough in the use of superconducting magnets at room temperature, the metal or alloy of gadolinium magnetic refrigerator for cooling medium has come out.
Terbium (Tb): 1, for the three-color phosphor in fluorescent green powder activator, such as terbium-activated phosphate matrix, terbium activated silicate matrix, terbium-activated cerium magnesium aluminate matrix, in Under both the excited state emits green light. 2, a magneto-optical storage materials, in recent years, a magneto-optical material terbium-based mass production scale has been reached, with the development of Tb-Fe amorphous thin film magneto-optical disc, a computer memory element for storage capacity increased by 10 to 15 times. 3, magneto-optical glass, glass containing terbium Faraday rotation is made in laser technology widely used in rotation, isolators and circulators key material. Especially Terfenol alloy (TerFenol) developed, it is opening up new uses for terbium, when placed in a magnetic field when the Terfenol, change its dimensions than the average magnetic variation in this change may make some Precision mechanical movement can be achieved. Terbium and dysprosium iron began mainly used sonar, has been widely used in a variety of areas, from the fuel injection system, the liquid valve control, micro-mechanical actuator positioned to regulate areas such as wing regulator bodies and aircraft Space Telescope.
Dysprosium (Dy): 1, as an additive to the use of NdFeB permanent magnets, adding about 2 to 3% of dysprosium in such magnets, the coercive force can be improved, the demand for small dysprosium past, but with the NdFeB magnets increase demand, it became necessary to add elements, quality must be about 95 to 99.9%, demand is also increasing rapidly. 2, used as a phosphor activator dysprosium, dysprosium (III) is a promising one-color light-emitting center of the light emitting material of active ionic species, it is mainly composed of two emission bands, one for yellow light emission, blue light emission and the other is , dysprosium-doped luminescent materials can be used as three-color phosphor. 3, dysprosium is preparing a large magnetostrictive alloy terbium and dysprosium iron (Terfenol) alloy metal material necessary, make some precision mechanical movement activities can be achieved. 4, can be used as a magneto-optical storage dysprosium metal material having a higher recording speed and reading sensitivity. 5, for the preparation of dysprosium lamps, work lamps substance dysprosium dysprosium iodide is used in such lamps have brightness, good color, high color temperature, small, stable arc, etc., have been used in movies, and printing lighting. 6, because of dysprosium elements with large neutron capture cross-sectional area the property is used in the atomic energy industry, or do neutron spectrum measured neutron absorber. 7, Dy3Al5O12 also be used as magnetic refrigeration magnetic working material. With the development of science and technology, applications dysprosium will continue to expand and extend. 8. Photoluminescent pigment raw materials
Holmium (Ho): 1, used for metal halide additives, metal halide is a gas discharge lamp, which is developed on the basis of high-pressure mercury lamp, which is characterized by the light bulb filled with a variety of rare earth halide matter. At present, the use of rare earth iodide, emit different colors of light when the gas line discharge. In light of the working substance is used holmium holmium iodide, in the arc zone can obtain a higher concentration of the metal atoms, thereby greatly improving the radiation efficiency. 2, holmium yttrium iron can be used as additives or yttrium aluminum garnet. 3, holmium-doped yttrium aluminum garnet (Ho: YAG) laser can emit 2μm, human tissue for 2μm laser absorption rate than almost Hd: YAG high three orders of magnitude. So with the Ho: YAG laser at a medical surgery, surgery can not only improve the efficiency and accuracy, but can be reduced to a smaller area of thermal damage. Freedom holmium crystal beam generated to eliminate fat without generating excessive heat, thereby reducing thermal damage to healthy tissue, according to reports the United States with holmium laser treatment of glaucoma, can reduce the pain of surgery patients. Level of 2μm laser crystal has reached the international level, should be vigorously developed and produced this laser crystal. 4, the magnetostrictive alloy Terfenol-D, can also be added a small amount of holmium, the saturation magnetization of the alloy thereby reducing the required field. 5, another with a holmium-doped fiber can make fiber lasers, optical amplifiers, optical fiber sensors, etc. optical communication devices in today's fast optical fiber communication will play a more important role.
Erbium (Er): 1, Er3 + has a special significance in the light-emitting 1550nm Department, because the wavelength is just at the lowest loss optical fiber optical fiber communications, erbium ions (Er3 +) by the wavelength of 980nm, the light 1480nm excitation from the ground state 4I15 / 2 transition to high-energy states 4I13 / 2, light emitted from the wavelength of 1550nm when in the high energy state to the Er3 + ground state and then transitions back to the quartz optical fiber can transmit a variety of different wavelengths of light, but a different decay rate of the bare different, 1550nm optical band transmission time decay rate lowest (0.15 db / km) in a quartz fiber, almost decay rate lower limit limit. Therefore, the signal light for optical fiber communication at 1550nm, light loss is minimized. Thus, if an appropriate concentration of erbium incorporated into a suitable matrix may be based on the principle of laser action, the amplifier capable of compensating for losses in the communication system, and therefore the need to enlarge the optical signal wavelength of 1550nm in the telecommunications network, the erbium-doped fiber amplifier is indispensable a small optical device, the current amplifier is an erbium-doped silica fibers has been commercialized. It is reported that, in order to avoid unwanted absorption of the erbium-doped fiber amount of several tens to several hundreds ppm. The rapid development of optical fiber communications, will open up new areas of application of erbium. 2, the other erbium-doped laser crystals and output 1730nm and 1550nm laser laser eye safety of human, good atmosphere transmission performance, strong ability to penetrate battlefield smoke, confidentiality, and not be detected by the enemy, irradiation military contrast targets larger, has made eye-safe laser rangefinder, portable military use. 3, Er3 + is added to the glass can be made of rare earth glass laser materials, the output pulse energy is currently the largest and highest output power solid-state laser materials. 4, Er3 + laser material conversion can be done on the rare earth ion activated. 5, the other may be applied to glasses doped glass, crystallized glass of the bleaching and coloring and the like.
Thulium (Tm): 1, Tm used for medical X-ray radiation source, lightweight, thulium irradiated in a nuclear reactor to produce an isotope capable of emitting X-rays, can be irradiated to produce a portable blood analyzer, which can radiometer Tm -169 be so high neutron beam into effect thulium -170, and emits X-ray irradiation of the blood white blood cells decreased, and it is these leukocytes can cause organ transplant rejection, thereby reducing early organ rejection. 2, thulium elements can also be used in clinical diagnosis and treatment of tumors, tumor tissue because it has a higher affinity than the light rare HREE greater affinity, particularly in the largest pro-thulium elements together. 3, thulium activator LaOBr do in X-ray intensifying screen phosphors in: Br (blue), to enhance the optical sensitivity, thus reducing the X-ray exposure and hazards to human, with the previous phase calcium tungstate intensifying screens X-ray dose can be reduced more than 50%, which is of great practical significance in medical applications. 4, thulium can also make new additive metal halide lighting. 5, Tm3 + added to the glass can be made of rare earth glass laser material, which is currently the largest amount of output pulses, the maximum output power solid-state laser materials. Tm3 + laser material also can be converted on the rare earth ion activation.
Ytterbium (Yb): 1, as a heat shield coating material. Ytterbium can significantly improve the electrodeposited zinc coating corrosion resistance and coating containing ytterbium Yb ratio excluding coating fine grain, uniform and compact. 2, for the magnetostrictive material. This material has a super-magnetostrictive that expansion in a magnetic field characteristics. The alloy is mainly composed of ytterbium / ferrite alloy and dysprosium / ferrite alloy, and adding a certain percentage of manganese to produce giant magnetostrictive properties. 3, ytterbium element for measuring pressure, test proved that ytterbium element within the calibrated pressure range with high sensitivity, as well as pressure measurement applications ytterbium opened up a new way. , 4, molar empty resin-based filler commonly used in the past to replace amalgam. 5, Japanese scholars have successfully completed the preparation work ytterbium-doped gadolinium gallium garnet embedded waveguide laser line, the completion of this work on laser technology to further develop meaningful. Further, the phosphor is also used to activate the agent ytterbium radio ceramics, computer memory device (bubble) additives, and glass fiber additives, such as flux, and optical glass.
Lutetium (Lu): 1, the manufacture of certain special alloys. Such as lutetium aluminum can be used for neutron activation analysis. 2, the stable nuclide lutetium petroleum cracking, alkylation, hydrogenation, and catalytic polymerization. 3, yttrium iron or yttrium aluminum garnet add elements to improve certain properties. 4, the bubble reservoir materials. 5, a composite function of crystal doped lutetium, neodymium yttrium aluminum borate belongs to the technical field of cooled saline solution crystal growth experiment proved doped lutetium NYAB crystal optical uniformity and laser performance are better than NYAB crystal. 6, the foreign authorities found lutetium in electrochromic displays and low-dimensional molecular semiconductors have potential uses. In addition, lutetium battery technology is also used for energy and phosphor activated agent.
Yttrium (Y): 1, steel and non-ferrous alloy additives. FeCr alloys typically contain 0.5-4%, yttrium can enhance the oxidation resistance and ductility of stainless steel; MB26 alloy adding the right amount of yttrium-rich mixed rare earth alloy overall performance has been significantly improved, can replace part of the strong aluminum alloys are used for the force component of the aircraft; adding a small amount of rare earth in the yttrium-rich Al-Zr alloys, the alloy can increase the electric conductivity; the alloy has been used most domestic wire factory; yttrium was added in the copper alloy, to improve conductivity and mechanical strength. 2, 6% of yttrium and aluminum containing 2% of silicon nitride ceramic material, can be used to develop engine components. 3, with a power of 400 watts of neodymium yttrium aluminum garnet laser beam drilling, cutting and welding, machining of large components. 4, the electron microscope screen by Y-Al garnet single crystal composed of high fluorescence intensity, low absorption of scattered light resistance, high temperature performance and good resistance to mechanical wear. 5, Y yttrium up to 90% of high alloy structures containing aviation and may be applied to the low density and high melting point other requirements of the occasion. 6, the current much-doped yttrium SrZrO3 high temperature proton-conducting materials of concern, has important implications for the production of fuel cells, electrolytic cell, and require high solubility of hydrogen gas sensor. In addition, yttrium is also used for high-temperature coating material, nuclear reactor fuel diluents, additives and permanent magnetic materials for the electronics industry inhale agent.
Scandium (Sc): 1, in the metallurgical industry, the alloy used in the manufacture of scandium (alloy additive), in order to improve the strength, hardness and heat resistance and performance. For example, adding a small amount of iron, scandium, can significantly improve the performance of iron, a small amount of scandium added to the aluminum, which can improve the strength and heat resistance. 2, in the electronics industry, scandium used for various semiconductor devices, such as sulfites application of scandium in semiconductors have attracted attention at home and abroad, including scandium ferrite cores in the computer are also quite promising . 3, in the chemical industry, with the scandium compound as alcohol dehydrogenation and dehydration agent, a catalyst for producing ethylene and highly efficient production of chlorine by the time the waste hydrochloric acid. 4, in the glass industry, can be made of special glass containing scandium. 5, the electric light industry, scandium sodium and sodium-containing scandium made with high efficiency and light color are advantages. 6, scandium are 45Sc nature exist, in addition, there are nine kinds of scandium radioisotopes, namely 40 ~ 44Sc and 46 ~ 49Sc. Among them, 46Sc as a tracer, has been used in the chemical industry, metallurgy and other aspects of oceanography. 7, in medicine, there are people abroad with 46Sc to treat cancer research.
