Erbium(III) Fluoride
Properties
| State | Solid |
| Color | Pink |
| Solubility | Essentially insoluble in water; insoluble in organic solvents |
| Melting Point | 1150 °C |
| Boiling Point | 2200 °C |
About Erbium(III) Fluoride
Erbium(III) fluoride is the pink, water-insoluble counterpart of pink, water-soluble ErCl3 — both salts get their color from the same Er3+ f-f transitions, but the fluoride lattice is too stable to dissolve. ErF3 crystallizes in the β-YF3 orthorhombic structure (space group Pnma), the same heavy-lanthanide trifluoride structure type as DyF3, melts at 1150 °C, and resists hydrolysis even in boiling water — its Ksp is around 10^-24. That insolubility is the practical reason ErF3 is the dopant of choice for ZBLAN fluoride-glass fiber amplifiers, where the fluoride matrix needs to stay chemically intact during glass melting at 800-900 °C and during fiber drawing. The reason anyone cares about Er-doped fiber at all is the 4I13/2 → 4I15/2 transition near 1530 nm, which happens to be the wavelength of minimum loss in silica fiber. In silica, that transition is broadened by Si-O phonons to about 30 nm of usable gain bandwidth — fine for early EDFAs. In ZBLAN, with phonon energies roughly half of silica's, the gain spectrum is broader and flatter (50-80 nm), supporting much denser DWDM channel counts and higher per-fiber capacity. ErF3 is also the standard Yb-codoped upconverter — Yb3+ harvests 980 nm pump light and feeds energy sequentially to Er3+, populating high-lying levels that emit green at 525/545 nm and red at 660 nm. That two-photon upconversion is what powers anti-counterfeiting inks on currency and pharmaceutical packaging.
Where you'll encounter it
If you've handled ZBLAN fluoride-glass preforms in a fiber-laser lab, you've worked with ErF3 — typical doping levels are 0.5-2 mol% in the ZrF4-BaF2-LaF3-AlF3-NaF host, hand-blended as fluoride powders and melted under reactive atmosphere. The resulting fibers run 2.7 µm and 1.55 µm laser lines used for medical surgery and IR countermeasures. In a nanoparticle synthesis lab, ErF3 ends up in NaYF4:Yb,Er upconversion nanocrystals, which you can image by exciting at 980 nm and watching them light up green under a microscope — the basis for deep-tissue biological imaging that avoids tissue autofluorescence.
Common Uses
- Dopant in ZBLAN fluoride-glass fiber amplifiers for C-band and L-band DWDM telecom
- Activator in NaYF4:Yb,Er upconversion nanocrystals for deep-tissue bioimaging
- Gain-medium dopant in 2.7 µm and 1.55 µm mid-infrared fiber lasers
- Calcium metallothermic reduction feedstock for Er metal production
- Anti-counterfeiting upconversion phosphor in currency and pharmaceutical packaging
- Optical thin-film material for IR window coatings
- Reference compound for Er3+ luminescence quantum yield measurements
- Co-dopant in scintillator and storage-phosphor crystal growth
Safety Information
GHS H315/H319 (skin and eye irritation, Category 2/2A). Low acute toxicity (LD50 > 5 g/kg orally in rat) — the lattice is stable enough not to release significant fluoride at physiological pH. Acid digestion (HNO3 or HCl) generates HF, so any sample-prep procedure for ICP-MS analysis needs hood work, calcium gluconate gel on hand, and PTFE labware. OSHA PEL for soluble fluorides is 2.5 mg/m3 as F. Long-term inhalation of rare-earth fluoride dust has been associated with pulmonary fibrosis in refinery cohorts.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.