Terbium
lanthanideProperties
| Property | Value |
|---|---|
| Atomic Mass | 158.93 amu |
| Category | lanthanide |
| Period | 6 |
| Electron Configuration | [Xe] 4f9 6s2 |
| Electronegativity | 1.2 (Pauling) |
| Oxidation States | 3, 4 |
| Melting Point | 1629 K (1355.8 °C) |
| Boiling Point | 3503 K (3229.8 °C) |
| Density | 8.23 g/cm³ |
| Discovered By | Carl Gustaf Mosander (1843) |
About Terbium
Terbium is one of four elements named after a single Swedish quarry at Ytterby, and chemistry pulled it out of yttria the hard way — Mosander spent years separating Mosander's three oxides into yttria, erbia, and terbia by repeated fractional crystallization. What earns Tb its place in modern equipment is the Tb³⁺ ion's ⁵D₄ → ⁷F₅ transition, which fluoresces at exactly the green wavelength the human eye sees most efficiently. Doped into Y₂O₃ or LaPO₄ it became the green phosphor in tri-band fluorescent tubes, then in trichromatic LED phosphor blends, and it's the green channel in scintillators like Tb:GOS that medical X-ray detectors use. The other side of Tb chemistry is mechanical: Terfenol-D (Tb₀.₃Dy₀.₇Fe₂) is the highest-strain magnetostrictive alloy at room temperature, expanding about 0.15% in a moderate field. That's the actuator behind low-frequency Navy sonar transducers and bone-conduction speakers built into eyewear.
Fun Fact
Four elements — terbium, yttrium, erbium, and ytterbium — are all named after the tiny Swedish village of Ytterby, making it the most element-rich place name in the history of chemistry.
Common Uses
- Tb³⁺-doped LaPO₄ green phosphor in tri-band fluorescent tubes and white LEDs
- Tb:Gd₂O₂S scintillator screens in medical X-ray flat-panel detectors
- Terfenol-D magnetostrictive transducers for naval sonar projectors
- Magneto-optical recording layers in early Sony MiniDisc media
- Stabilizer dopant in Tb-zirconia solid-oxide fuel-cell electrolytes
- Lanthanide tag (Tb-DOTA) in time-resolved fluorescence immunoassays