Europium oxides

Europium oxide is now widely used as a phospor activator and europium-activated yttrium vanadate is in commercial use as the red phosphor in color TV tubes. Europium-doped plastic has been used as a laser material. With the development of ion-exchange techniques and special processes, the cost of the metal has been greatly reduced in recent years. 

Europium oxides Europrene AR Europrene N Europrene Sol T S. eurythermus Euxenite... 

In order to make an efficient Y202 Eu ", it is necessary to start with weU-purifted yttrium and europium oxides or a weU-purifted coprecipitated oxide. Very small amounts of impurity ions, particularly other rare-earth ions, decrease the efficiency of this phosphor. Ce " is one of the most troublesome ions because it competes for the uv absorption and should be present at no more than about one part per million. Once purified, if not already coprecipitated, the oxides are dissolved in hydrochloric or nitric acid and then precipitated with oxaflc acid. This precipitate is then calcined, and fired at around 800°C to decompose the oxalate and form the oxide. EinaHy the oxide is fired usually in air at temperatures of 1500—1550°C in order to produce a good crystal stmcture and an efficient phosphor. This phosphor does not need to be further processed but may be milled for particle size control and/or screened to remove agglomerates which later show up as dark specks in the coating. 

The HFBR core uses fully-enriched (93%) uranium oxide-aluminum cermet curved plates dad m aluminum. The core height is 0.58 m and the diameter is 0.48 m or a volume of 103.7 Itr. The U-235 weighs 9.83 kg supported by a grid plate on the vessel bottom. The coolant flow u downward. Iience. How reversal is necessary for natural circulation. It operating temperature and pressure are 60 ( and 195 psi. There are 8 main and 8 auxiliary control rod blades made of europium oxide (Lii A)o and dysprosium oxide (DyjO,), clad in stainless steel that operate in the reflector region. The scram system is the winch-clutch release type to drop the blades into the reflector region. Actuation of scram causes a setback for the auxiliary control rods which are driven upward by drive motors,... 

Europium oxide (EU2O3) nanorods have been prepared by the sonication of an aqueous solution of europium nitrate in the presence of ammonia. In this reaction, ammonium ions adsorbed on the Eu(OH)3 particles (formed due to the collapse of the bubbles) results in the formation of a monolayer which then fuse together by hydrogen bonding leading to the formation of nanorods [28]. 

Pol VG, Palchik O, Gedanken A, Felner I (2002) Synthesis of europium oxide nanorods by ultrasound irradiation. J Phys Chem B 106(38) 9737-9743... 

There are only a few commercial uses for europium. Europium oxide, (Eu O ), a compound of europium, is added to infra-sensitive phosphors to enhance the red colors on TV and computer-monitor picture tubes. It is also added to fluorescent light tubes to increase their efflciency, as well as to some materials to make lasers. Since it is a good neutron absorber, it is part of nuclear reactor control rods. Europium is an additive to the glue used on postage stamps, thus making it possible for the electronic sorting machines in U.S. postal offices to read the stamps. 

The discovery of samarium is credited to Boisbaudran, who in 1879 separated its oxide, samaria from Mosander s didymia, the mixture of rare earth oxides from which cerium and lanthanum were isolated earher. Demarcay in 1901 first identified samaria to be a mixture of samarium and europium oxides. The element got its name from its mineral, samarskite. The mineral, in turn, was named in honor of the Russian mine official Col. Samarki. 

Yttrinm and europium oxides form mixed crystals without any vacancies due to the very similar size of their ionic radii. Y OjiEu is used with around 3 mol% europium to give a very intense red phosphor (/L 612 run) that is used in colour CRTs. 

First exanple - In the production of red phosphors for color TV v re each screen requires about 5 - 10 g yttrium oxide and 500 - 1 000 mg europium oxide, high requirements are placed on the purity and with reference to specific rare earth elements or nan-rare earth elements. As a result, the prices are expressed in /g. 

A study was also made of a series of samples having a base composition 30Ba070B203, but, with varying europium concentrations with up to 5 per cent europium oxide, no significant departure from Beer s law or reduction in the lifetimes were found. 

The most successful of the anion emitters are based on rare earth oxide matrices, with the rare earth in the +3 oxidation state. Europium oxide, Eu703, is the most successful of these anion emitters and also has the most stable +2 oxidation state of all the rare earths. This feature of Eu203, the stability of the +2 oxidation state, is thought to be responsible for this compound s being the best matrix. Whereas the matrix in the +3 oxidation state allows the migration of the anions away from the counter ion, the stability of the +2 oxidation states allows reactions of the following type to take place ... 

Apart from the intrinsic interest in the process, there are a number of applications of pressure sintering. We mention two. First, this compaction permits the determination of the spectra of solids which cannot be obtained when the sample is in its usual form. For example, Conway (3) has determined the adsorption spectrum of gadolinium oxide down to 2000 A. A similar study is being made on europium oxide by Nathans (5). 

The electrical conductivity of rare-earth oxide fluorides was first investigated for the development of a binary anion conductive solid electrolyte. As a result, it was found that the binary rare-earth oxide fluorides exhibited oxide ion conductivity. Among them, the conductivity of neodymium europium oxide fluoride, Nd2Eu203F6, was reported to be much higher than that of yttria-stabilized zirconia, YSZ, practically used as an oxygen sensor [34]. The electrical conductivities of the binary rare-earth oxide fluorides vary not only with the combination of Ln203 with Ln F3... 

Europium oxide phosphors are also used in printing postage stamps. These phosphors make it possible for machines to read a stamp and know what its value is. If the wrong stamp is on a letter, the machine can tell from reading the phosphor. The machine will then send the letter back to the person who mailed it. 

Preparation of Nuclear Ceramic Materials 17.3.12.4. Control Rods 17.3.12.4.3. Europium Oxide. 

Use of europium oxide as a neutron absorber in the control rods avoids gas generation under irradiation and gives a slower loss of reactivity with neutron exposure than boron carbide (10%). The main problems are obtaining adequate critical nuclear... 

---