What are some rare elements used for?

Question

Really, what are some of those really heavy elements used for? Neodymium? Terbium? Even some of the lesser heavy ones like Yttrium I can't think of a use for!

Answer 1

Neodymium:

"Applications
Uses of neodymium include

Neodymium is a component of didymium used for colouring glass to make welder's goggles.
Neodymium colours glass in delicate shades ranging from pure violet through wine-red and warm grey. Light transmitted through such glass shows unusually sharp absorption bands; the glass is used in astronomical work to produce sharp bands by which spectral lines may be calibrated. Neodymium is also used to remove the green colour caused by iron contaminants from glass.
Neodymium salts are used as a colourant for enamels.
Neodymium is used in the strongest permanent magnets known - Nd2Fe14B. These magnets are cheaper, lighter, and stronger than samarium-cobalt magnets. Neodymium magnets appear in high-quality products such as microphones, professional loudspeakers, in-ear headphones and computer hard disks where low mass, small volume, or strong magnetic fields are required.
Probably because of similarities to Ca2+, Nd3+ has been reported [1] to promote plant growth. Rare earth element compounds are frequently used in China as fertilizer.
Size and strength of volcanic eruption can be predicted by scanning for neodymium isotopes. Small and large volcanic eruptions produce lava with different neodymium isotope composition. From the composition of isotopes, scientists predict how big the coming eruption will be, and use this information to warn residents of the intensity of the eruption.
Certain transparent materials with a small concentration of neodymium ions can be used in lasers as gain media for infrared wavelengths (1054-1064 nm), e.g. Nd:YAG (yttrium aluminium garnet), Nd:YLF (yttrium lithium fluoride), Nd:YVO4 (yttrium orthvanadate), and Nd:glass. The current laser at the UK Atomic Weapons Establishment (AWE), the HELEN 1-TW neodymium-glass laser, can access the midpoints of pressure and temperature regions and is used to acquire data for modelling on how density, temperature and pressure interact inside warheads. HELEN can create plasmas of around 106 K, from which opacity and transmission of radiation are measured.
Neodymium glass (Nd:Glass) solid-state lasers are used in extremely high power (terawatt scale), high energy (megajoules) multiple beam systems for inertial confinement fusion. Nd:Glass lasers are usually frequency tripled to the third harmonic at 351 nm in laser fusion devices"
From Wikipedia, the free, online encyclopedia at:
http://en.wikipedia.org/wiki/Neodymium

Terbium:
"Applications
Terbium is used to dope calcium fluoride, calcium tungstate and strontium molybdate, materials that are used in solid-state devices, and as a crystal stabilizer of fuel cells which operate at elevated temperatures, together with ZrO2. Terbium is also used in alloys and in the production of electronic devices, its oxide is used in green phosphors in fluorescent lamps and color TV tubes. Sodium terbium borate is used in solid state devices."
From Wikipedia at: http://en.wikipedia.org/wiki/Terbium

Yttrium:
"Applications
Yttrium(III) oxide is the most important yttrium compound and is widely used to make YVO4:Eu and Y2O3:Eu phosphors that give the red color in color television picture tubes. Other uses include:

Yttrium oxide is also used to make yttrium iron garnets which are very effective microwave filters.
Yttrium iron, aluminium, and gadolinium garnets (e.g. Y3Fe5O12 and Y3Al5O12) have interesting magnetic properties. Yttrium iron garnet is very efficient as an acoustic energy transmitter and transducer. Yttrium aluminium garnet has a hardness of 8.5 and is also used as a gemstone (simulated diamond).
Small amounts of the element (0.1 to 0.2%) have been used to reduce grain size of chromium, molybdenum, titanium, and zirconium. It is also used to increase the strength of aluminium and magnesium alloys.
Used as a catalyst for ethylene polymerization.
Yttrium aluminium garnet, yttrium lithium fluoride, and yttrium vanadate are used in combination with dopants such as neodymium or erbium in infrared lasers.
This metal can be used to deoxidize vanadium and other nonferrous metals.
Yttrium is also used in the manufacture of gas mantles for propane lanterns, as a replacement for thorium, which is slightly radioactive.
Cerium-doped yttrium aluminium garnet (YAG:Ce) crystals are used as phosphors to make white LEDs.
Yttrium was used as a "secret" element in a superconductor developed at the University of Houston, YBaCuO. This superconductor operated above 90K, an amazing feat because it can operate at above liquid nitrogen's boiling point. (Y1.2Ba0.8CuO4). The matter created was a multi-crystal multi-phase mineral, of which were black and green.
Yttrium has been studied for possible use as a nodulizer in the making of nodular cast iron which has increased ductility (the graphite forms compact nodules instead of flakes to form nodular cast iron). Potentially, yttrium can be used in ceramic and glass formulas, since yttrium oxide has a high melting point and imparts shock resistance and low thermal expansion characteristics to glass."
From Wikipedia at: http://en.wikipedia.org/wiki/Yttrium

Hope this helps!

Answer 2

Neodymium..strong magnets
Terbium....sodium terbium borate is used in lasers
Yttrium...color TV screens

Answer 3

All kinds of industrial and engineering applications.

Rare earth magnets: http://www.rare-earth-magnets.com/ (used in electronics of all kinds from cars to dvd drives)

http://pubs.usgs.gov/fs/2002/fs087-02/
Cathode ray tubes, liquid crystal displays, fiber optics cables, glass polishing agents, processing petroleum, etc.