Samarium oxides

AHoys can be produced by the coreduction process, carried out at 1000°C with calcium, from the oxide mixture. For example, samarium oxide [12060-58-1] and cobalt oxide are coreduced to a SmCo [12017-68-4] powder, CaO then being removed. 

Calciothermic reduction of samarium oxide, in the presence of cobalt powder, yields samarium-cobalt alloys in the powder form. The process is popularly known as reduction diffusion. Samarium oxide, mixed with cobalt powder and calcium hydride powder or calcium particles, is heated at 1200 °C under 1 atm hydrogen pressure to produce the alloys. Cobalt oxide sometimes partly replaces the cobalt metal in the charge for alloy preparation. This presents no difficulty because calcium can easily reduce cobalt oxide. A pelletized mixture of oxides of samarium and cobalt, cobalt and calcium, with the components taken in stoichiometric quantities, is heated at 1100-1200 °C in vacuum for 2 to 3 h. This process is called coreduction. In reduction diffusion as well as in coreduction, the metals samarium and/or cobalt form by reduction rather quickly but they need time to form the alloy by diffusion, which warrants holding the charge at the reaction temperature for 4 to 5 h. The yield of alloy in these processes ranges from 97 to 99%. Reduction diffusion is the method by which most of the 500 to 600 t of the magnetic samarium-cobalt alloy (SmCOs) are produced every year. 

Yahiro, H. Eguchi, Y. Eguchi, K. Arai, H. 1988. Oxygen ion conductivity of the ceria samarium oxide system with fluorite structure. I. Appl. Electrochem. 18 527-531. 

The first sample we tested was samarium oxide, and we found it to be very radioactive. Now we know today that the radioactive isotope is samarium-147 with a half life of 105,000,000,000 years, and that the radiation is an emission of helium ions (alpha... 

Mosander extracted from the mineral lanthana a rare earth fraction, named didymia in 1841. In 1879, Boisbaudran separated a rare earth oxide called samaria (samarium oxide) from the didymia fraction obtained from the mineral samarskite. Soon after that in 1885, Baron Auer von Welsbach isolated two other rare earths from didymia. He named them as praseodymia (green twin) and neodymia (new twin) after their source didymia (twin). The name praseodymium finally was assigned to this new element, derived from the two Greek words, prasios meaning green and didymos meaning twin. 

Samarium reduces several metal oxides to metals. Such metal oxides include iron, zinc, lead, chromium, manganese, tin, and zirconium. When heated with carbon monoxide, it forms samarium oxide and carbon. 

Synonyms samariumflll) oxide, samarium oxide samaria... 

TABLE II - WORLD PRODUCTION OF SAMARIUM OXIDE EXPRESSED IN TERMS OF DERIVED ALLOYS... 

Another completely different approach consists in choosing a dye, that already possesses aminocarboxylate functions (Meshkova et al., 1992a), such as triphenylmethane dyes. The latter can be used for selective luminescent determination of Nd111 and Ybm in samarium oxide, for instance. As previously described in the section devoted to /3-diketonates (section 3.2.1), the triplet excited states of /i-dikctonatcs lie at energies >20 000-25 000 cm-1, above most of the accepting levels of Lnm ions. As a consequence, determination of Ndm and Yb111 in europium or samarium oxides is difficult using /3-dike to nates since these two ions exhibit luminescence in the NIR, especially Smm with emission lines at 908, 930, 950, and 1038 nm close to the analytical lines of Ndm and Ybm. Therefore, the detection limit of Ndm and Ybm in samarium compounds by luminescence of their ternary complexes with tta and phen is only 0.1-1 wt%. 

For various types of catalyst there are results of kinetic investigations for the oxidative dehydrogenation of ethane available (e.g., for a magnesium oxide catalyst doped with samarium oxide, lithium nitrate and ammonium chloride [64] or a V2O5/Y-AI2O3 catalyst [68]). In another study with a Sn.oLai.oNdi.oOx catalyst, investigations were reported of noncatalytic reactions, which were found to be significant at temperatures above 700 °C [69]. 

Rare earth oxides are useful for partial oxidation of natural gas to ethane and ethylene. Samarium oxide doped with alkali metal halides is the most effective catalyst for producing predominantly ethylene. In syngas chemistry, addition of rare earths has proven to be useful to catalyst activity and selectivity. Formerly thorium oxide was used in the Fisher-Tropsch process. Recently ruthenium supported on rare earth oxides was found selective for lower olefin production. Also praseodymium-iron/alumina catalysts produce hydrocarbons in the middle distillate range. Further unusual catalytic properties have been found for lanthanide intermetallics like CeCo2, CeNi2, ThNis- Rare earth compounds (Ce, La) are effective promoters in alcohol synthesis, steam reforming of hydrocarbons, alcohol carbonylation and selective oxidation of olefins. 

Lanthanide (III) Oxides. The lanthanide(III) oxides will be used to illustrate the present breadth of our most extensive knowledge of the chemical thermodynamics of lanthanide compounds. Cryogenic heat capacities of hexagonal (III) lanthanum, neodymium, and samarium oxides, together with those of cubic (III) oxides of gadolinium, dysprosium, holmium, erbium, and ytterbium, have been reported (90, 91, 195). In addition, those of thulium, lutetium, and a composition approaching that of cerium (III) oxide have also been determined, and five well-characterized compositions between PrOi.714 and PrOi.833 are currently under study (J93). 

The lanthanides react slowly with cold water (more rapidly with hot water) to form hydrogen gas, and readily bum in air to form oxides. Oxides are substances in which a metal and oxygen have chemically combined to form a compound. For example, samarium and oxygen combine to form the compound samarium oxide. Yttrium has a natural protective oxide coating, making it much more resistant. The lanthanides form compounds with many nonmetals, such as hydrogen, fluorine, phosphorous, sulfur, and chlorine, and heating may be required to induce these reactions. 

Samarium can be obtained by heating samarium oxide (Sm203) with barium or lanthanum metal ... 

The only compound of samarium with any commercial applications is samarium oxide (Sm203). This compound is used in the manufacture of special kinds of glass, as a catalyst in the manufacture of ethanol (ethyl alcohol), and in nuclear power plants as a neutron absorber. 

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