Terbium

=**Terbium**= a chemical element with the symbol **Tb** and atomic number 65. It is a silvery-white rare earth metal that is malleable, ductile, and and soft enough to be cut with a knife. Terbium is never found in nature as a free element, but it is contained in many minerals, including cerite, gadolinite, monazite, xenotime and euxenite. 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. As a component of Terfenol-D (an alloy that expands and contracts when exposed to magnetic fields more than any other alloy), terbium is of use in actuators, in naval sonar systems and sensors. The largest consumer of the world's terbium supply is in "green" phosphors (which are usually yellow). Terbium oxide is in fluorescent lamps and TV tubes. Terbium "green" phosphors (which fluoresce a brilliant lemon-yellow) are combined with divalent europium blue phosphors and trivalent europium red phosphors to provide "trichromatic" lighting technology, a high-efficiency white light used for standard illumination in indoor lighting.


 * Name:** Terbium
 * Symbol:** Tb
 * Atomic Number:** 65
 * Atomic Mass:** 158.92534 amu
 * Melting Point:** 1360.0 °C (1633.15 K, 2480.0 °F)
 * Boiling Point:** 3041.0 °C (3314.15 K, 5505.8 °F)
 * Number of Protons/Electrons:** 65
 * Number of Neutrons:** 94
 * Classification:** Rare Earth
 * Crystal Structure:** Hexagonal
 * Density @ 293 K:** 8.27 g/cm3
 * Color:** silverish

**Harmful effects**: Terbium is considered to be moderately toxic. Terbium does not tarnish rapidly in air and it is soft enough to be cut with a knife. Its oxide terbia (Tb2O3) is a white powder and the heptaoxide (Tb4O7) is a dark maroon color. The heptaoxide contains terbium in both its +3 and +4 oxidation states. Terbium exists in two crystal allotropes with transformation at a temperature of 1289 oC. Tb3+ ions emit a strong green luminescence when excited.
 * Characteristics: ** Terbium is a silver gray rare earth metal that is both malleable and ductile. Like other rare earth metals, it forms 3+ ions. Unlike most, it also forms 4+ ions relatively easily.

Uses of Terbium
The luminescence of Tb3+ is important in a significant number of applications. Terbium is used in color phosphors in lighting applications such as trichromatic lighting and in color TV tubes. It also makes the green color on your Blackberry or other high definition screen. Tb3+ ions can be used to check for the presence of microbes. Terbium chloride is applied to the test area, which is then illuminated with UV light. Within minutes, any live endospores present will glow green. Euro banknotes use rare earth chemistry to defeat counterfeiters. Shining UV light on a euro results in green fluorescence from terbium Tb3+, red from europium Eu3+, and blue from thulium Tm3+. A terbium-iron alloy is used to provide metallic films for magneto-optic recording of data. Hybrid car engines have electric motors and all electric motors are based on magnets. These magnets need to retain their magnetism at high temperatures. Alloying neodymium with terbium and dysprosium produces such magnets. These magnets are also used in the electric motors of wind-turbines, where high temperatures are also generated. Terfenol-D (a terbium, iron and dysprosium alloy) expands or contracts in the presence of a magnetic field (magnetostriction). It is used in a speaker called the 'SoundBug', which turns any flat surface into a speaker. The 'SoundBug' vibrates any material it is placed on, such as a table or desk, making it into a speaker. Terbium is also used as a dopant for materials in solid-state devices and optical fibers.