The chemical element europium: basic properties and applications. Application area europium Hydrogen energy
Europium is a chemical element in the periodic table. It is used in energy, medicine and electronics and is the most expensive representative of the lanthanides. What are the properties and characteristics of europium?
Element 63
The chemical element europium was first discovered by the Englishman William Crookes in 1886. But its properties did not become known immediately. Repeatedly, Crookes and other scientists saw only spectral lines of a substance unknown to them. Its discovery is attributed to the Frenchman Eugene Demarce, who not only discovered the element, but also isolated it from the mineral, described it and gave it a name.
Europium is a metal with atomic number 63. It is not found in independent form and occurs naturally in rare earth minerals such as monazite and xenotime. Amount of the chemical element europium in earth's crust is 1.2 * 10 -4%. For industrial production, the metal is extracted from monazite, since its content in this mineral reaches up to 1%.
The largest deposits of europium are located in Kenya. It is also found in the USA, Brazil, Australia, Scandinavian countries, Russia, Kazakhstan, etc.
Main characteristics
The chemical element europium is a silvery metal white. Its atomic mass is 151.964 (1) g/mol. It is soft and easily amenable to mechanical action, but only under an inert atmosphere, since it is a fairly active substance.
The melting point of the metal is 826 degrees Celsius, europium boils at a temperature of 1529 degrees. It can become superconducting (gaining the ability to have zero electrical resistance) at a pressure of 80 GPa and a temperature of -271.35 Celsius (1.8 K).
There are two natural isotopes of the element europium 153 and europium 151 with different neutron contents in the nucleus. The first one is quite stable and is slightly more widespread in nature. The second isotope is unstable and exhibits alpha decay. The period of the chemical element europium 151 is 5×10 18 years. In addition to these isotopes, there are 35 more artificial ones. The longest is Eu 150 (half-life 36.9 years), and one of the fastest is Eu 152 m3 (half-life 164 nanoseconds).
Chemical properties
The chemical element europium belongs to the lanthanide group, along with Lanthanum, Cerium, Gadolinium, Promethium and others. He is the lightest and most active of all his “classmates.” Europium quickly reacts with air, oxidizing and becoming covered with a film. Because of this, it is usually stored in paraffin or kerosene in special containers and flasks.
Europium is also active in other reactions. In compounds it is usually trivalent, but sometimes it is divalent. When heated in an oxygen atmosphere, it forms the compound Eu 2 O 3 in the form of a white-pink powder. When heated slightly, it easily reacts with nitrogen, hydrogen and halogens. Many of its compounds are white with light shades of orange and pink.
Europium (III) cations are obtained by decomposition of solutions of sulfate, oxalate, and nitrate salts. In industry, the metal is produced using carbon or lanthanum by reducing its oxide or electrolysis of its alloy EuCl 3.
Of all the lanthanides, only the emission spectrum of europium(III) ions can be discerned by the human eye. When used to generate laser radiation, the color of its beam is orange.
Application
The chemical element europium has found application in the field of electronics. In color television it is used to activate red or red phosphors. of blue color. Its combination with silicon EuSi 2 forms thin films and is used to make microcircuits.
The element is used for production fluorescent lamps and fluorescent glass. In medicine, it was used to treat some forms of cancer. Its artificial isotope europium 152 serves as an indicator, and the isotope numbered 155 is used for medical diagnostics.
It absorbs thermal neutrons more strongly than other lanthanides, which is very useful in nuclear energy. For these purposes, its oxide, a compound with boric acid(europium borate) and a binary compound with boron (europium hexaboride). The element is also used in atomic hydrogen energy during the thermochemical decomposition of water.
Harm and impact on humans
Europium is found in small quantities in the human body. It can also be contained in water, entering it in areas of mineral deposits in which it is included. Industrial production also supplies water with this element.
The effect of the element on the human body and health has not been studied. Trusting the widespread information, it does not pose a particular danger, since its concentrations are usually too low.
Europium has very little toxicity, and its content in water is usually so small that it cannot significantly affect its quality. In fresh and low-salt waters its amount reaches 1 µg/l, sea water this figure is 1.1*10 -6 mg/l.
The last rare earth element of the cerium subgroup - europium - just like its neighbors on the periodic table, is one of the most powerful absorbers of thermal neutrons. This is the basis for its use in nuclear technology and radiation protection technology.
As an anti-neutron protection material, element No. 63 is interesting because its natural isotopes 151 Eu and 153 Eu, absorbing neutrons, are converted into isotopes whose cross section for capturing thermal neutrons is almost as large.
Radioactive europium produced in nuclear reactors has been used to treat some forms of cancer.
Europium has gained importance as an activator of phosphors. In particular, yttrium oxide, oxysulfide and orthovanadate YV0 4, used to produce red color on television screens, are activated by micro-impurities of europium. Other phosphors activated by europium are also of practical importance. They are based on zinc and strontium sulfides, sodium and calcium fluorides, calcium and barium silicates.
It is known that attempts were made to alloy some special alloys with europium, separated from other lanthanides, in particular zirconium-based alloys.
Element No. 63 is not like other rare earth elements in every way.
- the lightest of the lanthanides, its density is only 5.245 g/cm 3 . Europium has the largest atomic radius and atomic volume of all lanthanides. Some researchers also associate these “anomalies” in the properties of element No. 63 with the fact that of all the rare earth elements, europium is the least resistant to the corrosive action of moist air and water.
Reacting with water, europium forms a soluble compound Eu(0H) 2 *2H 2 0. It is yellow in color, but gradually turns white during storage. Apparently, further oxidation by atmospheric oxygen to Eu 2 0 3 occurs here.
As is known, trivalent ions of many lanthanides can be used, like the Cr 3+ ion in ruby, to excite laser radiation. But of all of them, only the Eu 3+ ion produces radiation in the part of the spectrum perceived by the human eye. The europium laser beam is orange.
Origin of the name europium
Where the name of element No. 63 comes from is not difficult to understand. As for the history of the discovery, it was difficult and long to discover.
In 1886, the French chemist Demarsay isolated a new element from Samara earth, which was, apparently, not pure europium. But his experience could not be reproduced. In the same year, the Englishman Crookes discovered a new line in the spectrum of samarskite. Lecoq de Boisbaudran made a similar message six years later. But all the data about the new element were somewhat shaky.
Demarsay showed character. He spent several years isolating a new element from samarium earth and, having finally prepared (this was already in 1896), a pure preparation, he clearly saw the spectral line of the new element. Initially, he designated the new element with the Greek capital letter “sigma” - 2. In 1901, after a series of control experiments, this element received its current name.
Metallic europium was first obtained only in 1937.
"Europeum"
Completed by: student of group YaF-42
Zharlgapova Aida
Checked by: Zhumadilov K.Sh.
Astana, 2015
History of discovery
The discovery of europium is associated with the early spectroscopic work of Crookes and Lecoq de Boisbaudran. In 1886, Crookes, while studying the phosphorescence spectrum of the mineral samarskite, discovered a band in the wavelength region of 609 A. He observed the same band when analyzing a mixture of ytterbium and samarium earths. Crookes did not give a name to the suspected element and temporarily designated it with the index Y. In 1892, Lecoq de Boisbaudran received 3 g of purified samarium earth from Cleves and carried out its fractional crystallization. After spectroscopy of the resulting fractions, he discovered a number of new lines and designated the supposed new element with the indices Z (epsilon) and Z (zetta). Four years later, Demarsay, as a result of long-term painstaking work on isolating the desired element from samarium earth, clearly saw a spectroscopic band of an unknown earth; he gave it the index "E". It was later proven that Lecoq de Boisbaudran's Z(epsilon), and Z(zetta), Demarsay's "E", and the anomalous spectral bands observed by Crookes, belong to the same element, named by Demarsay in 1901 as Europium in honor of the continent of Europe.
EUROPIUM(Europium), Eu - chemical. element of group III periodic. systems of elements, at. number 63, at. mass 151.96, part of the lanthanide family. Natural E. consists of isotopes with mass numbers 151 (47.82%) and 153 (52.18%). Electronic configuration of three ext. shells 4s 2 p 6 d 10 f 7 5s 2 p 6 6s 2. Energy and research ionizations are 5.664, 11.25 and 24.7 eV. Crystalchem. the radius of the Eu atom is 0.202 nm (the largest among the lanthanides), the radius of the Eu 3+ ion is 0.097 nm. The electronegativity value is 1.01. In free form - silvery-white metal, body-centered cubic crystal lattice with lattice constant a= 0.45720 nm. Density 5.245 kg/dm 3, t pl =822 °C, t boil =1597 °C. Heat of fusion 9.2 kJ/mol, heat of evaporation 146 kJ/mol, sp. heat capacity 27.6 J/mol.K, sp. resistance 8.13.10 -5 Ohm.cm (at 25 °C). Paramagnetic, magnetic susceptibility 22.10 -8. In chem. compounds exhibit oxidation states +2 and +3. Natural isotopes of E. have high thermal neutron capture cross sections, so E. is used as an eff. neutron absorber. Eu serves as an activator in decomposition. phosphors based on compounds Y, Zn, etc. Lasers based on ruby activated Eu 3+ produce radiation in the visible region of the spectrum. Of the radionuclides, most What matters are (b - -radioactive 152 Eu (T 1/2 = 13.33 g) and 154 Eu (T 1/2 = 8.8 g), used in g-flaw detection and other purposes.
For the ROSFOND library it was necessary to select neutron data for 12 stable and long-lived isotopes of europium. Data for all these isotopes are contained in the FOND-2.2 library. However, as will be seen below, it would be advisable to replace neutron data for a number of isotopes with more modern and complete estimates made in last years. Let us consider the results of the re-evaluation of data for europium isotopes carried out in recent years in comparison with the estimates contained in FUND-2.2. In this case, we will pay main attention to the results of assessing the capture cross section. All experimental data used in comparison with the estimated cross sections were taken from the EXFOR-CINDA database (version 1.81, June 2005). Recommended Muhabhab values are given according to the work “Thermal Neutron Capture Cross Sections, Resonance Integrals and G-factors”, INDC(NDS)-440, 2003. Radioactive isotopes. There are no complete neutron data sets for the 6 long-lived dysprosium isotopes –145Eu, 146Eu, 147Eu, 148Eu, 149Eu and 150Eu. In the FOND-2.2 library, neutron data for them were taken from EAF-3. In the EAF-2003 version of the library, the data on radioactive neutron capture for the most part remained practically unchanged, but the remaining cross sections were revised taking into account calculations using programs that implement new theoretical models. Of particular note are the long-lived isotopes 152Eu, 154Eu, 155Eu and 156Eu, for which complete sets of neutron data were available. These isotopes are characterized by large cross-sections radiation capture and long lifetime. They are fission products that make a noticeable total contribution to the total absorption cross section of all fission products. Stable isotopes. Data for stable europium isotopes in the FOND-2.2 library were taken from the JENDL-3.3 library with slight data correction (March 1990). The changes concerned the revision of cross sections for threshold reactions. The JEF-3.1 library for Eu-151 uses the estimate made for JEF-2.2 (~ENDF/B-V). For Eu-153, an estimate made for the Japanese neutron data library JENDL-3.2. The neutron data in the JENDL-3.3 library has not been revised since the JENDL-3.2 version (March 1990). ENDF.B-VII (betha 1.2 version, November 2005) adopts the assessment carried out as part of the project to create an international fission product library. Authors of the assessment: Muhabhab (S.Mughabghab, BNL) - (resonance area); Oblozhinsky (P. Oblozinsky, BNL), Rochman (D. Rochman, BNL) and Herman (M. Herman, BNL) - (higher energy region. When analyzing neutron data for individual isotopes, we will proceed from that general information which is stated above. Europium-152 The Eu-152 isotope is formed by burning off the stable isotope Eu-151. It has three isomeric states. In the ground state - half-life T1\2=13.516 years. From which the isotope, with ~70% probability, undergoing β-decay turns into the stable isotope Gd-150 (α-active), and with ~30% probability, as a result of positron decay, turns into Sm-152. In the first isomeric state, the half-life is 9.31 hours. The decay chain is similar to the ground state, with the only difference being that the probabilities of the decay processes have swapped places. The probability of an isomeric transition is negligible. In the second isomeric state (T1\2=96 min.) it experiences an isomeric transition to the ground state with the emission of a γ-quantum. In FOND-2.2 – assessment by J. Kopecky, D. Nierop, 1992 (EAF-3). In JEFF-3.1 – evaluation performed for JENDL-3.2. In JENDL-3.3 - evaluation done for JENDL-3.2 with minor modifications, 1990. In ENDF/B-VII b1.2 - evaluation by R. Wright and JNDC FPND W.G. (2005) for the international fission product library. In the region of allowed resonances (1.E-5 eV – 62.07 eV) the ENDF/B estimate was used, above – the JENDL-3.3 estimate. Some characteristics for the resonant energy region are given in Table 2. They were obtained using the INTER program from the ENDF UTILITY CODES software package (release 6.13, July 2002). From the information presented in Table 2, it can be seen that both the ENDF/B estimate and the JENDL estimate are consistent with the experimental value of the capture cross section. Note that there is a strong discrepancy between the value of the resonance integral recommended by Muhabhab (BNL-325, 1981) and the values obtained from the estimated cross sections. It is also clear from the tabular data that the assessment adopted by the FUND needs to be revised. Figure 10 shows a comparison of the estimated cross sections for radiative neutron capture in the resonant energy region. From the comparison shown in Figure 10, it can be seen that the ENDF/B estimate significantly expands the range of allowed resonances. When describing resonances in the region of 2 eV, the ENDF/B estimate is higher than the JENDL estimate, which causes small discrepancies in the value of the resonance integral between these estimates.
Application area europium
Europium metal, designation according to Russian standards EvM-1 according to TU 48-2-217-72, ingots, chemical purity 99.9% or more. They belong to rare earth elements (cerium subgroup of lanthanides). Located in group 111 in the 6th period periodic table Europium is the lightest of the lanthanides. It is also unstable among rare earth elements - in the presence of atmospheric oxygen and moisture it quickly oxidizes (corrodes). Europium is the most active and one of the most expensive lanthanides. Used as a financial instrument. Technical Application europium the following:
1. Nuclear power: Europium is used as a neutron absorber in nuclear reactors, the most active in terms of neutron capture is europium-151. this provides highly effective protection against hard radiation over a wide wavelength spectrum.
2. Nuclear-hydrogen energy: Europium oxide is used in the thermochemical decomposition of water in atomic-hydrogen energy (Europium-strontium-iodide cycle).
3. Laser materials: Europium ions are used to generate laser radiation in the visible region of the spectrum (orange rays), so europium oxide is used to create solid-state, liquid lasers.。
4. Electronics: Europium is a dopant in samarium monosulfide (thermoelectric generators), and also as an alloying component for the synthesis of diamond-like (superhard) carbon nitride. Europium silicide in the form of thin films is used in integrated microelectronics.
5. Europium monoxide is used in the form of thin films as magnetic semiconductor materials for rapidly developing functional electronics, and in particular MIS electronics
6. Phosphors: Europium tungstate is a phosphor used in microelectronics and television. Strontium borate is doped with europium and is used as a phosphor in black light lamps.
7. Europium in medicine: Europium cations are successfully used in medicine as fluorescent probes. Radioactive isotopes of Europium are used in the treatment of certain forms of cancer.
8. Other uses of europium: Photosensitive compounds of europium with bromine, chlorine and iodine are being intensively studied. Europium-154 has high power heat release during radioactive decay and has been proposed as a fuel in radioisotope energy sources. Some special alloys, in particular zirconium-based alloys, are doped with europium, separated from other lanthanides.
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