Rare earth is a group of metallic elements, including No.21 scandium,No.39 yttrium, and from No.57 lanthanum to No.71 Lutetium in periodic table. The discovery of the total rare earth elements took 135 year as much. On account of their similarities, it is not 40's of the century, until that the pure rare earth individuals were not prepared in commercial scale except a small quantity obtained in laboratory. At that time, the pure rare earth individuals were expensive, as such strictly limited their application.
In 1947, Some American scientists developed an effective separation process called ion exchange, then the process was used to separate adjacent rare earth element and successful. F.H.spedding improved the process, by thus this method, high purity rare earth individual compounds in kg scale were prepared.
In 1958, solvent-solvent extraction commenced coming to be used to group separation in a large scale production line. In 1964 pure Europium, Yttrium, Lanthanum oxide were produced by this process, which effectively inspired rare earth industry. Up to 1980'America mining amount was over 25300 tons(REO).
Owing to the abounding of rare earth mineral resources, and the making use of the new extraction: 2-ethylhexyl phosphate mono-(2-ethylhexyl) ester (Developed by Daihachi chemical industrial Co.,ltd) China exceed America in separation capacity for the first time in 1986. China possesses 70% rare earth mineral resources of the globe. The most famous mine in the world is Baiyunebo in Boutou Inner Mongolia which main ingredient is light rare earth. In south China the most important mine is called ion absorption type, which major constitution is heavy rare earth.
China's mining quantum of rare earth in 1995 accounted for 70% of total production in the world. Now, China has become the biggest supplier of rare earth over the world. Nowadays, rare earth in indispensable. The teems below will show you main uses of rare earth. We believe that the rare earth family will play an important role in human life in the coming century definitely.
2. WORLD RESERVES OF RARE EARTH MINERALS AND THEIR DISTRIBUTION:
There is large amount of reserves of rare earth minerals in the world. The largest proved reserves are located in China. Other important reserves of rare earths are located in Australia, Russian Federation, United States, Brazil, Canada and India. In Vietnam. In addition, some deposits of rare earths was found in South Africa, Malaysia, Indonesia, Sri Lanka, Mongolia, North Korea, Afghanistan, Saudi Arabia, Turkey, Norway, Greece and Nigeria, Kenya, Tanzania, Burundi, Madagascar, Mozambique and Egypt.
Deposits with reserves of more than Mt are as follows:
Baiyun Obe iron-niobium-rare earth deposit in Inner Mongolia in China;
Bastnaesite deposit in Sichuan in China;
Ion adsorption clays in Southern provinces in China;
Mount Weld monazite deposits associated with carbonate intrusions in Australia;
Heavy beach san placer deposits in Australia;
Bastnaesite deposit at Mountain Pass in USA;
Alaxia; Zaislagushi rare earth deposit associated with wethering carbonate in Brazil;
Tuomutur rare earth deposit associated with wethering carbonate in Russia;
Shibin rare earth deposit associated with phosphate and nepheline;
Maosai rare earth deposit in Vietnam.
According to relevant statistical datum, the proportion of Chinese rare earths reserves in world rare earths reserves as a whole decreased to about 69% in 1980s and 45% in 1990s from 74% in 1970s as results of discovering of large and super-large rare earth deposits in Australia, Russia, Canada, Brazil and Vietnam, but China is still the largest country reserves of rare earths in the world, moreover,it has large undefined reserves of rare earths. It is believed that this situation could be maintained for a long time.
3. THE MAIN APPLICATION OF RARE EARTH
1.Metallurgy: de-oxygen de-sulfur, and other injurious ingredients to act reducing agent.
2.Flint, ignition device
3.catalyst for problem crack
4.Automobile exhaust gas crack
5.Glass ceramic clearing, de-coloring agent, anti-ultraviolet glaze
6.Permnent magnets SmCo,NdFeB
7.Super-conductor
8.Functional ceramic, yttria+zirconia
9.Phosphor for color TV, ceria+zirconia
10.Hydrogen storage, secondary battery
11.Polishing powder
12.Laser material, optical fiber optical lens
13.Magnentic forced extant-contract material
14.Substitution of poisonous Cd pigments
Rare Earth Oxides
RE oxide are most stable from various RE compounds, the fundamental raw material of other compounds and are basic products of raw material in RE industry. RE oxides are generally prepared by ignition of corresponding hydroxide, oxalate, carbonate salt, nitrate salt, soleplate salt in the air. RE oxide are insoluble in water and basic solution, soluble in strong mineral acids, and apt to absorb cabin dioxide from air to form carbonate salt. All RE oxide are powder and their melt points are above 2300℃.
Rare earth hydroxides
RE Hydroxides are generally prepared by mixing corresponding soluble salt with ammonium hydroxide or sodium hydroxide they are soluble in acids, insoluble in water, and generally powder.
Rare earth Chlorides
There are two kinds of RE chlorides, anhydrous and hydrous chlorides. The former is prepared by heating, dewater in vacuum of it's hydrous. The Later is prepared by condensing of its corresponding RE chloride solution. All RE chlorides are hydroscopic and substantially soluble in water.
Rare earth Sulphates
RE sulphates are generally prepared by adding sulphuric acid to their corresponding oxides, hydroxides, carbonates, and the solid state of the salt can be prepared by condensation of the solution. All RE sulphates are soluble in water, but their solubilities are lower and down with the temperature up.
Rare earth Carbonate
The solid RE carbonate can be prepared by adding more the solution of soluble RE salt. RE carbonates are little soluble in water, soluble in acids to yield corresponding salt and give off CO2 RE carbonates decompose to be oxides over 905℃.
Rear earth Nitrate Hydrous
RE nitrates can be prepared by condensing the solution of their salt which are obtained by mixing the nitric acid and RE oxide, hydroxide, carbonate. RE nitrates are most soluble in water of various salt and soluble in some organic agents-alcohol acetone etc. When the salts are heated, give off 02,NO,N02,the final products are oxides.
Rear earth Fluorides
RE fluorides are prepared by adding HF solution RE salt solution are insoluble in water, soluble in thick acid, and the major raw material for electrolysis of RE metal.
Rear Earth Metals
RE metals appear as of typical metallicity. Their melt points and densities increase with the atomic number except Europium and ytterbium, yet the hardness increases with the atomic number in spite of being soft. Although their tensile stresses are low, RE metals show fairly high stretchy .The activities of the Metals increase in sequence in Sc,Y,La, however decrease from La to Lu sequentially. The metals are liable to oxidize in the air, inert in cool water, but active to hot water and realease hydrogen and violently react with acids, but rather inactive to bases. The metals are combustible. As such should be kept carefully. Normally, RE metals are manufactured by electrolysis or pyroreduction. RE metals are rather effective reductants in metallurgical, the metals have been used to prepare high performance magnetics, fuel batteries, secondary cells, and functional non-ferrous materials.
5. RARE EARTH OXIDES FORMULA WEIGHT
| Atomic
Symbol |
Atomic
Number |
Atomic
Weight |
Rare
earth
Oxide |
F.Wt | Half F.Wt |
| La | 57 | 138.905 | La2O3 | 305.8 | 162.9 |
| Ce | 58 | 140.12 | CeO2 | 172.1 | 172.1 |
| Pr | 59 | 140.908 | Pr6O11 | 1021.4 | 170.2 |
| Nd | 60 | 144.2 | Nd2O3 | 336.4 | 168.2 |
| Sm | 62 | 150.4 | Sm2O3 | 348.8 | 174.4 |
| Eu | 63 | 151.96 | Eu2O3 | 351.9 | 176.0 |
| Gd | 64 | 157.2 | Gd2O3 | 362.4 | 181.2 |
| Tb | 65 | 158.925 | Tb4O7 | 747.7 | 186.9 |
| Dy | 66 | 162.5 | Dy2O3 | 373.0 | 186.5 |
| Ho | 67 | 164.93 | Ho2O3 | 377.9 | 188.9 |
| Er | 68 | 167.2 | Er2O3 | 382.4 | 191.2 |
| Tm | 69 | 168.93 | Tm2O3 | 385.87 | 192.93 |
| Yb | 70 | 173 | Yb2O3 | 394.0 | 197.0 |
| Lu | 71 | 174.96 | Lu2O3 | 397.9 | 199.0 |
| Sc | 21 | 44.9559 | Sc2O3 | 137.91 | 69.0 |
| Y | 39 | 88.9059 | Y2O3 | 225.8 | 112.9 |
6. RARE EARTH STANDARD ELECTRODE POTENTIAL
| Acidic solution | V | Alkaline solution | V |
| La3++3e=La | -2.522 | La(OH)3+3e=La+3OH- | -2.9 |
| Ce3++3e=Ce | La(OH)3+3e=La+3OH- | ||
| Ce4++e=Ce3+ | La(OH)3+3e=La+3OH- | ||
| Pr3++3e=Pr | La(OH)3+3e=La+3OH- | ||
| Nd3++3e=Nd | La(OH)3+3e=La+3OH- | ||
| Sm3++3e=Sm | La(OH)3+3e=La+3OH- | ||
| Sm3++e=Sm2+ | La(OH)3+3e=La+3OH- | ||
| Eu3++3e=Eu | La(OH)3+3e=La+3OH- | ||
| Gd3++3e=Gd | La(OH)3+3e=La+3OH- | ||
| Tb3++3e=Tb | La(OH)3+3e=La+3OH- | ||
| Dy3++3e=Dy | La(OH)3+3e=La+3OH- | ||
| Er3++3e=Ho | La(OH)3+3e=La+3OH- | ||
| Ho3++3e=Er | La(OH)3+3e=La+3OH- | ||
| Tm3++3e=Tm | La(OH)3+3e=La+3OH- | ||
| Yb3++3e=Yb | La(OH)3+3e=La+3OH- | ||
| La3++3e=La | La(OH)3+3e=La+3OH- | ||
| La3++3e=La | La(OH)3+3e=La+3OH- | ||
| La3++3e=La | La(OH)3+3e=La+3OH- | ||
| La3++3e=La | La(OH)3+3e=La+3OH- |
7. PHYSICAL PROPERTIES OF RARE EARTH METALS
Atomic Numbe |
Atomic Symbol |
Atomic Weight |
Ionic Radius(A) |
Density |
Melting Point (oC) |
Boiling Point(oC) |
Oxide's Melting Point(oC) |
Specific Resistance |
Magnetic Moment |
Thermal Neutron Capture Cross Section |
57 |
La |
138.92 |
1.22 |
6.19 |
920+/-5 |
4230 |
2315 |
56.8 |
0.00 |
8.9 |
