Origin of the names and usage of the 17 rare earth elements

Lanthanum (La)

The element, “Lanthanum” is named in 1839 by Sweden Mosander, with the “didymia” in Greek when he found the elements in the ceria. From that on, lanthanum started to appear on the stage of history.

The application of lanthanum is very extensive.  For example, this element can be used in the piezoelectric materials, electro-thermal materials, thermoelectric materials, magneto-resistance materials, optical materials (such as the phosphor), hydrogen storage materials, optical glass, laser materials and other varieties of alloy materials, etc.  In addition, lanthanum is also applied into the catalysts of many organic chemical products.  The light-transformed agricultural film also adopts the lanthanum.  In foreign countries, the lanthanum is honored as the “Super Cal” due to its functions on the crops.

Cerium (Ce)

The element “Cerium” was found and named by the German, Klaproth and the Swedish, Berzelius and Hisinger in 1803, to memorize the asteroid-Ceres, founded in 1801.

The applications of the cerium are as follows: (1) as the additives of glass, which can absorb the ultraviolet rays and infrared rays, having been applied to the glass of vehicles extensively.  Except for protecting from the ultraviolet rays, it can also reduce the temperature inside the car and then save the electricity used by the air-conditioner.  From 1997, all the vehicles glass of Japan is added the cerium oxide.  In 1996, the amount of cerium oxide used in the vehicle glass in Japan is 2000 tons at least, while that of America is more than 1000 tons. (2) Currently, cerium is also applied in the automobile exhaust catalysts, which can effectively prevent from emission of the automobile exhaust into the air.  In America, the amount of the cerium used as the automobile exhaust catalysts is more than one third of the total consumption of the rare earth. (3) The cerium sulfide can be applied into the pigments instead of the metals hazardous to the environment and human beings, such as lead and cadmium, to color the plastics, or be used in the industries of coatings, printing inks and paper, etc.  For this area, Rhone-Poulenc Société Anonyme in France is in the leading position. (4) Ce:Li SAF laser system is a solid-state laser researched and developed by America, which can be used to explore the biological weapons by monitoring the concentration of tryptophan or in medicine.  The application of cerium is so extensive that almost all the fields applying the rare earth containing cerium, such as in the polishing power, hydrogen storage materials, thermoelectric materials, tungsten-cerium electrode, ceramic capacitors, piezoelectric ceramics, cerium silica carbide abrasives, raw materials of fuel cells, gasoline catalysts, some permanent magnetic materials, all kinds of alloy steels and non-ferrous metals, etc.

Praseodymium (Pr)

About 160 years ago, the Sweden Mosander discovered a new element, which is not the single element and has similar properties of lanthanum.  Therefore, Mosander named the element as “praseodymium neodymium”, which means “twins” in Greek.  About 40 years past, that is, 1885 when the gas lamps mantles were invented, the Austrian Welsbach successfully separated two elements from “praseodymium neodymium”, with one named “neodymium” and the other named “praseodymium”. After the separation of the “twins”, the element of praseodymium starts to have its own stage to exploit its functions.

Praseodymium, as the rare earth element with the largest consumption, is mainly used in glass, ceramics and magnetic materials.  The purposes of praseodymium are as follows: (1) praseodymium is extensively applied in the construction ceramics and daily used ceramics. The pigmented glazes made of it mixed with the ceramic glaze can be used as the pigments in the color of canary yellow with pure and elegant hue individually; (2) the antioxidant activity and mechanical performance of the permanent magnetic materials manufactured with the cheap praseodymium neodymium metals instead of the pure neodymium metals can be improved obviously and these permanent magnetic materials can be processed into the magnets in different shapes, which can be applied into electronic devices and engines broadly; (3) used for the petroleum catalytic cracking. The concentrates of praseodymium are added into the Y zeolites to prepare and make the catalysts of petroleum cracking, to improve the activation, selection and stability of the catalysts.  These catalysts have been put into use in industry in 1970s with the consumption still rising; (4) praseodymium also can be used in the abrasives for polishing.  In addition, praseodymium is also broadly applied in the field of optical fiber.

Neodymium (Nd)

With the appearance of praseodymium, neodymium was also born at the right moment.  The appearance of neodymium makes the rare earth field much more active. In the field of rare earth, neodymium plays an important role and has a determinant influence on the rare earth market.

Owning to the special status of neodymium in the field of rare earth, it has been the focus of the market for many years.  What consume the largest amount of neodymium metals are the NdFeB permanent magnetic materials, whose appearance has brought new vitality and vigor into the high-tech area of rare earth.  Due to the high magnetic energy product of NdFeB magnets, they are regarded as the “King of permanent magnets”, and extensively applied in the industries of electronics and machinery thanks to the excellent performances.  The success of the research and development of the Alpha Magnetic Spectrometer symbolizes all the magnetic performances of the NdFeB magnets having reaching the first level of the world.  Apart from this, neodymium is also used in the non-ferrous metal materials. Adding 1.5% to 2.5% neodymium into the magnesium alloy or aluminum alloy can improve the high temperature property, air tightness and anti-corrosion of the alloy, which has been broadly used as the aerospace materials.  In addition, the short-wave laser beam produced by the yttrium aluminum garnet contained neodymium has been extensively used to weld or cut the thin materials with the thickness below 10mm.  In medicine, the laser made of yttrium aluminum garnet contained neodymium is used to removal operation and wound sterilization instead of the scalpels.  Neodymium is also used as the colorant for the glass and ceramic materials and the additives of the rubber products.  With the development of the science and technology and the extension of the field of the science and technology of rare earth, neodymium can be applied more and more broadly.

Promethium (Pm)

In 1947, J.A.Marinsky, L.E.Glendenin and C.E.Coryell succeeded to separate the 61st element from the uranium fuel used in the atomic reactors. They called this element as “Promethium”, which originated from the name of “Prometheus” in the Greek myth.

Promethium is the artificial radioactive element produced from the nuclear reactors.  The main purposes of promethium are as follows: (1) as the heat sources to provide auxiliary energy for the vacuum detector and man-made satellites; (2) the Pm147 can used to manufacture the promethium batteries due to its emission of the β rays with low energies.  These batteries can be used as the power sources of the guidance instruments of missiles and clocks.  This kind of batteries with small volumes can be used for several years consecutively.  In addition, promethium also can be applied to manufacture the portable X-ray instruments, prepare and make phosphor, measure the thickness and make the pharos.

Samarium (Sm)

In 1879, Boisbaudran discovered the new rare earth material in the praseodymium neodymium from the samarskite and then named this element as samarium according to the name of the ore.

Samarium is in pale yellow. It is the raw material of the samarium-cobalt permanent magnets, which is the earliest rare earth magnets applied to the industry.  These permanent magnets can be classified into two categories, SmCo5 and Sm2Co17 with the former developed in the early 1970s and the latter developed in the late 1970s.  At present, the demand of the Sm2Co17 is the main. The samarium oxide used in the samarium-cobalt magnets is not required to have high purity. From the perspective of cost, the samarium oxide with the purity of 95% is the main products used in the samarium-cobalt magnets.  In addition, the samarium oxide is also used in the ceramic capacitors and the catalysts.  Besides, due to the nuclear property of samarium, it also can be used as the structural materials, shielding materials and control materials of the atomic reactors to use the tremendous energies produced by the nuclear fission safely.

Europium (Em)

In 1901, Eugene-Antole Demarcay found a new element from samarium and named it as “Europium”, which was originated from the word “Europe”.  The europium oxide is mostly used in the phosphor, with Eu3+ as the activator of the red phosphor and Eu2+ as the activator of blue phosphor.  At present, the Y2O2S:Eu3+ is the phosphor with the best luminous efficiency, coating stability and recovering cost, etc.  With the improvement of the luminous efficiency and contrast, the Y2O2S:Eu3+ is applied extensively.  In recent year, the europium oxide is also used in the stimulated radiation phosphor of the new type X-ray medical diagnosis system.  In addition, the europium oxide also can be used to manufacture the color glasses and optical filters and used in the storage devices of magnetic bubbles.  The europium oxide also plays a vital role in the control materials, shielding material and structural material of the atomic reactors.

Gadolinium (Gd)

In 1880, the Sweden G.de Marignac separated samarium into two elements, with one testified by the Sorin as the element of samarium, and the other researched and determined by Boisbaudran.  In 1886, to memorize the discoverer of the element gadolinium, that is, the Dutch chemist Gado Linium engaged in the research upon rare earth, G.de Marignac named the new element as gadolinium.

Gadolinium will pay an important role in modern technology revolution.  The main purposes of gadolinium include: (1) in medicine, its water-soluble paramagnetic complex can improve the imaging signal of NMR of human body; (2) the gadolinium oxysulfide can be used as the oscillograph tubes with special brightness and the matrix grid of X-ray fluorescent screen; (3) the gadolinium in the gadolinium gallium garnet can be used as the most ideal monolithic of the magnetic bubbles memory storage devices; (4) under the condition without the limitation of Camot circulation, the gadolinium can be used as the solid-state magnet cooling medium; (5) used as the depressor to control the chain reactions of the nuclear power station to guarantee the security of nuclear reactions; (6) as the additives of the samarium-cobalt magnet to ensure its performance would not change with the change of the temperature.  In addition, using the gadolinium oxide and lanthanum together is helpful for the change of the glass transition areas and the improvement of the thermal stability of the glass.  The gadolinium oxide can also be applied to manufacture the capacitors and the X-ray intensifying screen.

At present, all the countries in the world are making endeavors to develop the application of the gadolinium and gadolinium alloy in magnetic refrigeration, and have got a breakthrough.  The magnetic refrigerator adopted the superconducting magnet, metal gadolinium or the gadolinium alloy as the cooling medium in the room temperature has emerged.

Terbium (Tb)

The Sweden Karl G.Mosander discovered the element of terbium in the research of the yttria in 1843. Terbium is mostly used in the technology and knowledge intensive advanced projects with significant economic benefits and attractive developing prospects involved in the fields involved high technologies.  Terbium is mainly used in the following fields: (1) used as the activator of the green phosphor in the ternary phosphor, such as the phosphate matrix activated by the terbium, silicate matrix activated by terbium and cerium magnesium aluminate matrix activated by terbium, all of which emit green light; (2) used in the magneto-optical materials for storage components, which has been produced to a large scale in recent years.  Using the magneto-optic disk developed with the Tb-Fe amorphous thin film as the storage component of computers can improve the storage capability to ten to fifteen times; (3) used in the magneto-optical glass.  The faraday rotator glass contained terbium is the key materials of the rotators, isolators and circulators extensively applied in the laser technology.  In particular, the research and development of the TerFenol has created a new application of terbium.  TerFenol is a new-type material discovered in the 1970s, with terbium and dysprosium (sometimes with holmium) as half components and the ferrite as the rest components.  This alloy was primarily researched and developed by the Ames Laboratory in Iowa in America.  When put in a magnetic field, the size change of the TerFenol will be larger than that of the common magnetic materials, which makes the precise mechanical movement realized.  The TeDyFe alloy is initially applied in sonar.  At present, it has been applied in many areas, such as the fields of the fuel injection system, liquid valve control, micro-positioning, machined actuator, adjuster of the space telescope and the regulator of the aircraft wings, etc.

Dysprosium (Dy)

In 1886, the French Boisbaudran successfully separated holmium into two elements, with one called holmium and another called dysprosium, which means it was difficult to get from holmium.  At present, dysprosium has played a more and more important role in many high-tech fields.  The main applications of dysprosium are as follows: (1) used as the additives of NdFeB permanent magnets. If adding 2% to 3% of dysprosium into the magnet, its coercivity will be improved.  In the past, the demand of dysprosium was not large, while with the increase of the demand of the NdFeB magnets, the grade of the dysprosium, as the indispensable added element, shall be 95% to 99.9%, and the demand of dysprosium increases rapidly; (2) used as the activator of phosphor. Trivalent dysprosium, as the activating ion of the prosperous ternary luminous materials with single luminescence center, is made up of two emission bands, with one in yellow and the other in blue.  The luminous materials contained dysprosium can be used as the ternary phosphor; (3) used as the metal raw material to prepare and make the large magnetostrictive TerFenol alloy to make some machined movements realized; (4) used as the magneto-optical storage material, which has higher speed of recording and higher sensitivity of reading; (5) used to make the dysprosium lamps, which adopt the dysprosium iodide.  Such lamps have many advantages, such as much brighter, beautiful color, high color temperature, small volume, and stable arc, etc, and have been applied as the lighting sources on films and printing; (6) due to the large area of the capturing section of neurons, the dysprosium can be used to test the neutron spectrum or as the neutron absorption agent in atomic industry; (7) Dy3A15012 can be used the magnetic substance for magnetic refrigeration. With the development of science and technology, the applications of dysprosium will be expand more and more broadly.

Holmium (Ho)

In the latter of the 19th century, the discovery of the spectrometer method, the publish of the periodic table of the elements and the development of the technology of electrochemical separation of the rare earth elements have contributed to the discovery of new rare earth element. In 1879, the Swedish Cleve found the Holmium element, and named it as “holmium” based on the name of the capital of Sweden, Stockholm.

The application of holmium needs further development at present.  The consumption of holmium is not very large.  Recently, Rare Earth Research Institute in Baotou Iron & Steel (Group) Co. Ltd developed out the high-pure metal holmium with very low content of the non-rare earth impurities, Ho/ΣRE>99.9%, by adopting the high-temperature and high vacuum distillation and purification technology.  The main purposes of holmium are as follows: (1) used as the additives of the metal halide lamps, which are a kind of gas-discharge lamp, developed based on the high-pressure mercury lamps, with different rare earth halides filled in the bubbles.  For this purpose, it mainly uses the rare earth iodides, which can make the bubbles emit spectral lines in different colors.  In the holmium lamps, the substance used is holmium iodide, which can get higher metal atomic concentration in the arc area and then improve the radiation effects significantly; (2) used as the additives of yttrium iron garnet and yttrium aluminum garnet; (3) the yttrium aluminum garnet (Ho:YAG) contained holmium can emit 22μm laser, which can be absorbed by the human body at a higher rare, which is three orders of magnitude more than that of the Hd:YAG.  Therefore, using the Ho:YAG laser in the medical operation will not only improve the operation efficiency and precision, also can minimize the thermal damage area.   The free beam produced by the holmium crystals can eliminate the fate without excessive-heat produced, and then thermal damage to the healthy tissues.  It is reported that, in America, using the holmium laser to treat the glaucoma can reduce the pains of the patients in operation.  The 2μm laser crystals in our country have reached the international level.  Therefore, such laser crystals shall be developed and produced vigorously; (4) adding a little bit of holmium into the magnetostrictive alloy, TerFenol-D, can reduce the external magnetic field needed in the saturation magnetization of the alloy; (5) the fiber contained holmium that can be used to manufacture optical fiber laser, optical fiber amplifier, optical fiber sensor and other optical communication devices will play a more important role in today with the optical fiber communication developing rapidly.

Erbium (Er)

Erbium was discovered by the Sweden Mosander in 1843. The optical property of erbium is so outstanding that it becomes the public concerns: (1) Er3+ plays a special role for the light emission with the wave length of 1550nm.  Due to that the wave length equals to the minimum loss of the optical fiber of optical fiber communication, the Er3+ will jump from the ground state of 4I15/2 to high energy state of 4I13/2 after the excitation of the lights with wave length of 980nm and 1480nm.  When Er3+ jumps from the high energy state to the ground state, it will emit the lights with the wave length of 1550nm.  The silica optical fiber can transmit the lights with different wave lengths.  However, for the different lights, the light failure rates are different.  The light failure rate of the lights with the wave length of 1550nm transmitted with the silica optical fiber is lowest (0.15db/km), which almost equals to the minimum of the limited light failure rate.  Therefore, taking the optical fiber communication at the point of 1550nm as the optical signal, the light loss is the minimum.  In this way, if adding proper concentration of erbium into the proper base materials, according to the principle of laser, the amplifier can complement the loss of the communication system.  Therefore, in the communication network needing to amplify the optical signal with the wave length of 1550nm, the amplifier of optical fiber contained erbium is the indispensible instrument.  At present, the amplifier of silicate fiber contained erbium has realized the commercialization.  It is reported that to avoid the useless absorption, the content of erbium in the optical fiber is decades to hundreds of ppm.  The rapid development of optical communication will pave new fields for the application of erbium; (2) the laser crystals contained erbium, and the 1730nm laser and 1550nm laser output from the laser crystals are all safe for the eyes.  The property of atmospheric transmission of the laser crystals is so good that they can permeate through the smoke of the gunpowder in the battle fields.  The confidentiality of the laser is so good that it is difficult for the enemies to discover.  The contrast of irradiating the military target is larger. Based on the above advantages of the laser crystals, they have been used to manufacture the portable laser range finder safe for the eyes in military; (3) Tm3+ can be used to manufacture the laser materials of rare earth glass when added into the glass, which are the solid-state laser materials with the largest output pulse and highest output rating;  (4) Er3+ also can be used as the active ion to transform the rare earth into laser materials; (5) erbium can be used as the colorant or decolorant for the glass of the glasses and glass ceramics.

Thulium（Tm）

Thulium was discovered by the Sweden Cleve, and named with the old name of Scandinavia, “Thule”, as “Thulium”.

The main purposes of thulium are as follows: (1) used as the portable ray sources of X-ray generators used in medicine.  After irradiation in the nuclear reactions, thulium can produce a isotope hat can emit X-ray, which can be used to manufacture the portable blood irradiator, which will make the thulium-169 transformed into thulium-170 with the action of high flux neutron beam and emit X rays to irradiate the blood and reduce the white blood cells.  Then due to the organ transplanting rejection resulted from these white blood cells, the situation of early rejection of organ declines; (2) thulium can also be used in the clinical diagnosis and tumor treatment because of it high affinity with the tumor tissues.  The affinity of heavy rare earth is larger than that of the light rare earth, especially thulium with the largest affinity; (3) as the activator of the phosphor used in the X ray intensifying screen to enhance the optical sensitivity and then reduce the radiation and hazards of the X ray to human body.  Compared with the past calcium-tungstate intensifying screen, this intensifying screen can reduce 50% of the X ray, which has great actual significance on the medical application; (4) used as the additives of the metal halide lamps, a new type light sources; (5) Tm3+ can be used to manufacture the laser materials of rare earth glass when added into the glass, which are the solid-state laser materials with the largest output pulse and highest output rating.  In addition, Tm3+ also can be used as the active ion to transform the rare earth into laser materials.

Ytterbium (Yb)

In 1878, the Swiss chemist Jean Charles and G. de Marignac discovered a new rare earth element in “erbium”, which was called as Ytterbium by Ytterby.

The main purposes of ytterbium are as follows: (1) as the heat-shielding coating materials. Ytterbium can improve the anti-corrosion property of the electrodeposited zinc coatings and the grains of the coating contained ytterbium is much smaller and more homogeneous than that of the coating not contained ytterbium; (2) as the magnetostriction materials, which has super magnetostrictive property, that is, the characteristic of expansion in the magnetic field.  The alloy is mainly constituted by ytterbium ferrite alloy and dysprosium ferrite alloy with a certain portion of ytterbium is added to make it has the super magnetostrictive property; (3) as the ytterbium components to measure the pressure, which is tested to be high sensitive within the standardized range of pressure and find a new way of ytterbium to measure the pressure; (4) as the fillers of the resin of molar cavities to replace the past common-used silver amalgam; (5) the Japan scholar successfully accomplished the preparation and making of the laser guided by the line waves embedded with gadolinium gallium garnet contained ytterbium, which has great significance for the further development of the laser technologies.  In addition, ytterbium is also used in the activator of phosphor, radio ceramics, additives of the memorizing components of the computers (magnetic bubbles), fluxing agent of glass fiber and the additives of optical glass, etc.

Lutetium (Lu)

Lutetium was independently discovered in 1907 by French scientist Georges Urbain and Austrian mineralogist Welsbach, who found the new element in the mineral ytterbium with different methods for separation.  Welsbach named this element as Cp (Cassiopeium), while Urbain name it as Lu (Lutetium) based on the old name of Paris, “Lutece”. Later, the scientists found Cp and Lu are the same element.  Therefore, it is collectively named as “Lutetium”.

The main purposes of Lutetium are as follows: (1) to make some special alloy, such as the lutetium-aluminum alloy that can used in the neutron activation analysis; (2) stable lutetium can be used as catalysts in petroleum cracking in refineries and can also be used in alkylation, hydrogenation, and polymerization applications; (3) as the additives of yttrium iron and yttrium aluminum garnet to improve some performance; (4) as the raw materials of the magnetic bubble reservoirs; (5) to add into the NYAB, which belongs to the field of the crystals grown in the cooling of the salt solutions. As the experiment testified, the NYAB with lutetium is much better in optical homogeneity and laser than the common NYAB crystals; (6) as the research of overseas relevant departments discovered, lutetium has some potential application in the electro-chromic display and low-dimensional molecular semiconductors.  In addition, lutetium also can be used in the energy battery technologies and the activator of phosphor, etc.

Yttrium (Y)

In 1788, Arrheniu, the military officer of Sweden, an amateur of researching upon chemistry, mineralogy and collecting ores, found a back ore with the appearance like the asphalt in Ytterby out of the Stockholm bay, and then called it as “Ytterbite” based on the name of the place.  In 1974, the Finnish chemist, Johan Gadilin, analyzed the sample of ytterbite.  He found except for the oxides of beryllium, silicate and iron, it also contains about 38% of oxides of unknown element, which he regarded as a “new soil”.  In 1797, the Swedish chemist Anders Gustaf Ekeberg defined the “new soil” and called it “Ytteria”, which means the yttrium oxide.

As a kind of metal with broad application, the main applications of yttrium include: (1) as the additives of steel and non-ferrous alloy.  FeCr generally contains 0.5% to 4% of yttrium, which can enhance the antioxidant activity and malleability of the stainless steels.  Adding proper amount of rare earth mixed and enriched with yttrium can improve the comprehensive performances of the alloy significantly.  This kind of alloy can be applied as the bearing components of the aircrafts instead of the medium-strength aluminum alloy.  Adding a little bit of yttrium into Al-Zr alloy can improve the electric conductivity of the alloy.  This alloy has been adopted by most of the electric circuit plants domestically.  Adding yttrium into the copper alloy can promote the conductivity and mechanical strength of the alloy; (2) the silicon nitride ceramic materials with 2% of yttrium and 2% of aluminum can be used to manufacture the components of the engines; (3) the neodymium yttrium aluminum garnet laser beam with 400watts of power can be used to process the large-scale component, such as drilling, cutting and wielding, etc.; (4) for the fluorescent screen of electron microscope constituted by the single chip of Y-Al garnet, the  fluorescence is much brighter, the absorption of scattered lights is low, and the performance of high temperature-resistance and anti-physical deterioration is much better; (5) the alloy contained 90% of yttrium can be applied in the aviation and other fields requiring low density and high smelting-point; (6) the SrZrO3 high-temperature proton conductive materials contained yttrium concerned by the public have vital significance for the production of the fuel batteries,  electrolytic cells and the gas sensitive elements with high hydrogen solubility required.  In addition, yttrium also can be used as the diluents of the high temperature-resistance spraying materials and fuel of the atomic reactions, additives of permanent magnetic materials and the getter in the electronic industry.

Scandium (Sc)

In 1879, the Swedish chemical profession, L.F.Nilson, (1840~1899) and P.T.Cleve (1840~1905) found a new element in the rare gadolinite and euxenite ores almost simultaneously, and name this element as “Scandium”, which is the “boron-like” element predicted by Mendeleev.  The discovery of scandium re-proves the correct of the periodic law of elements and the far insight of Mendeleev.

Compared with yttrium and lanthanum elements, the iron radius of scandium is particularly small and the alkalinity of the scandium hydroxides is particularly weak.  Therefore, mixing scandium and rare earth elements together, and disposing with ammonia (or extremely dilute alkali), scandium will be separated out primarily.  Due to this, using the method of fractional precipitation can separate scandium from the rare elements easily.  Another way is using the polarization decomposition of nitrate nitrogen to separate. Due to the easy decomposition of scandium nitrate, the scandium can be separated out easily.

The metal scandium can be got by the means of electrolysis.  In smelting scandium, smelting the ScCl3, KCl and LiCl together, using the smelted zinc as the negative electrode to electrolyze the scandium to make it separate out on the zinc electrode, and then distilling the zinc to get the metal scandium.  In addition, scandium is easy to be recovered in processing ores to produce uranium, thorium and lanthanum. Scandium associated in the comprehensive recycling of the tungsten and tin ores is also an important source of scandium.

In compounds, scandium is mainly three-valence.  In the air, it is easy to be oxidized into Sc203, and its color will be changed into dark grey.

Scandium can react with the hot water to produce hydrogen.  In addition, scandium is freely soluble in acid. It is a strong reducing agent.

Scandium oxides and scandium hydroxides are all alkaline.  However, the salt ash of the above substances is almost not soluble in water.  The scandium chlorides are the white crystals, which are soluble in water and can be deliquesced in the air.

In smelting industry, scandium is commonly used to manufacture alloy (additives of alloy), to improve the intensity, rigidity and heat-resistance property.  For example, adding a little bit of scandium into the molten iron can improve the performances of the cast iron greatly.

In electronic industry, it can be used to manufacture various semiconductor devices. For example, the application of scandium sulfite in the semiconductor has aroused the attentions at home and abroad.  The scandium ferrite also has a brighter future in the magnetic core of computer.

In glass industry, it can be used to manufacture the special glass contained scandium.

In chemical industry, the scandium compounds can used as the alcohol dehydrogenating agent and dehydrating agent and the high-efficient catalyst in producing ethylene and producing chlorine with waste hydrochloric acid.

In the industry of electrical lighting sources, the scandium sodium lamps made of scandium and sodium has higher efficiency and much purer color.

In nature, scandium is existed in the form of 45Sc.  In addition, there are nine radioactive isotopes of scandium, that is, the 40~44Sc and 46~49Sc, in which the 46Sc has been used in the chemical industry, smelting and maritime as the tracer. In medicine, some people in foreign countries are engaged in the research of 46Sc to treat cancers and the properties and applications of scandium.

Some physical properties of rare earth metals

  What is rare earth?

Rare earth refers to the lanthanide elements in the periodic table of chemical element, including La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and two elements related to the above 15 elements closely, Sc and Y. All these 17 elements are called rare earth or Re/R in short.
Rare earth elements are discovered in the relative rare ores in Sweden.  According to the customs of that period, “soil” refers to the substances insoluble in water.  Therefore, these elements are called rare earth.
According to the structure of the electron shell of atomics and the physical and chemical properties of the rare earth elements, and the symbiosis of them in the minerals and the different characteristics resulted from the different iron radiuses, the 17 rare earth element can be divided into two groups in general.
Light Rare Earth (the group of cerium): lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium and gadolinium;
Heavy Rare Earth (the group of yttrium): terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium and yttrium.
The reason why the two groups are called the group of cerium and the group of yttrium is that the cerium or yttrium is always in the largest proportion of the rare earth compounds separated from the minerals
The main physical and chemical properties of the rare earth elements
Rare earth elements are the typical metal elements, with the metal activity next to alkali metal and alkaline earth metals and stronger than other metal elements. Among the 17 rare earth elements, ranked by the metal activity, it increases from scandium, yttrium to lanthanum, and decreases from lanthanum to lutetium.  Therefore, lanthanum is the most active element.  The rare earth elements can form into oxides, halides and sulfides with stable chemical properties.  The rare earth elements can react with nitrogen, hydrogen, carbon and phosphorous and they are freely soluble in hydrochloric acid, sulfuric acid and nitric acid.
Rare earth elements are easy to combine with the element, such as oxygen, sulfur and lead, etc. and then produce the chemical compounds with high melting point.  Therefore, adding rare earth into the molten steel can purify the steel.  Due to that the atomic radiuses of rare earth elements are larger than the atomic radius of iron; it is easier to fill up the grains and defects with the rare earth elements to produce the film that can hinder the growth of the grains to make the grains much small to improve the performances of steel.
Due to the unfilled 4f electron shell structure, the rare earth elements can produce various electronic energy levels.  Therefore, rare earth can be applied as excellent phosphor, glazes of the laser and electric lighting materials, colored glass and ceramics.
The compounds of the rare earth ions with the hydroxyl group, azo group and sulfonic group make the rare earth extensive used in the printing and dyeing industry.  For some rare earth element with large area of the capturing section of neutrons, such as samarium, europium, gadolinium, dysprosium and erbium, they can be applied as the control materials or moderators in the atomic rations.  While for the rare earth element with small area of the capturing section of neutrons, such as cerium and yttrium, they can be applied as the diluents of the fuels of reactors.
The properties of rare earth similar to the microelements can drive the germination of the crop seeds, and contribute to the photosynthesis of plants.