66 DYSPROSIUM Dy (Greek: dysprositos = hard to obtain)

Dysprosium is a hard, silvery white metal belonging to the lanthanide series of the rare earth metals. It is relatively stable in air at room temperature, but is readily attacked and dissolved by dilute acids. The metal is soft enough to be cut with a knife and can be machined without sparking if overheating is avoided. Small amounts of impurities greatly affect its physical properties. Despite being soft, it has a high melting point of 1409ºC, and together with its thermal neutron capture cross section has found use in cooling nuclear control rods as the dysprosium oxide-nickel cermet, which readily absorbs neutrons without swelling or contracting under prolonged neutron bombardment. Paramagnetic at room temperature, dysprosium becomes ferromagnetic below 154K.

Dysprosium is a trivalent element of the lanthanide series, being the most basic of the erbium subgroup (Dy, Ho, Er, Tm) of the yttrium family. Dysprosium dioxide is white whilst dysprosium salts are yellow or green.

In combination with vanadium and other rare earths, dysprosium has been used in making laser materials. Dysprosium-cadmium calcogenides, as sources of infrared radiation, have been used for studying chemical reactions. Apart from gadolinium and terbium, it has the next highest magnetic susceptibility of any element, and has found uses as permanent magnets when alloyed with other metals.

Dysprosium is found, along with other rare earth elements, in a variety of minerals including xenotime; fergusonite, YNbO4; gadolinite, Be2FeY2Si2O10; euxenite; polycrase; and blomstrandine; the most important sources, however, are monazite, (Ce,La,Nd,Th)PO4; and bastanite.

Dysprosium exists as a mixture os seven stable isotopes, 28% of dysprosium-164, 25% each of dysprosium-163 and dysprosium-162, 19% dysprosium-161, 2% dysprosium-160, 0.1% dysprosium-158 and just 0.06% dysprosium-156. A total of 22 radioactive isotopes are known, ranging from the inverse beta decaying dysprosium-141 to the beta decaying dysprosium-169.

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