lanthanum(III) Oxide
Properties
| State | Solid |
| Color | white |
| Solubility | Insoluble in water; slowly soluble in dilute mineral acids |
| Melting Point | 2252 °C (approximate) |
About lanthanum(III) Oxide
Lanthanum(III) oxide is the white powder you get when you calcine almost any La-containing salt above 700°C — La2(CO3)3, La(OH)3, La(NO3)3, La oxalate all march to La2O3 + gas byproducts — and it's the standard commercial form in which lanthanum is shipped and stored before being converted to whatever downstream compound you actually want. La2O3 takes the A-type hexagonal rare-earth-sesquioxide structure (P-3m1, the same one Ce, Pr, Nd, Pm adopt at room temperature). At higher atomic numbers the lanthanide series shifts to monoclinic B-form (Sm-Gd) and then cubic bixbyite C-form (Tb-Lu) — the classic structural progression driven by the lanthanide contraction. The largest single use of La2O3 by tonnage is petroleum FCC catalyst manufacture: La-exchanged zeolite Y processes around 14 million barrels per day of crude globally, and refinery operators prize the La-stabilized form because the rare-earth ion cross-links framework Al-O-Si bonds and prevents dealumination during the 700°C steaming cycles in the regenerator. Other significant uses are in nickel-metal-hydride battery electrodes (LaNi5 alloys, the dominant chemistry in Toyota Prius hybrids until lithium-ion took over), high-refractive-index optical glass for camera lenses (La2O3 raises n from ~1.5 to >1.8 without raising dispersion the way TiO2 does), and as starting material for La metal via molten-salt electrolysis. Bulk La2O3 is faintly basic — it slowly absorbs CO2 and water from air to form the carbonate and hydroxide, so freshly calcined material is usually stored under argon.
Where you'll encounter it
If you've ever burned gasoline refined at a US, EU, or Chinese refinery — or used a digital camera with a high-end glass zoom lens — the supply chain almost certainly passes through La2O3 powder. Modern fluid catalytic cracking processes around 14 million barrels of crude oil per day worldwide, and every one of those FCC units relies on La-exchanged zeolite Y catalyst — La2O3 powder is the precursor for the ion-exchange step that stabilizes the framework against the 700°C steaming cycles in the regenerator. Camera lens designers use La2O3 to push glass refractive index above 1.8 without raising dispersion the way TiO2 would, which is why high-end Canon L-series and Nikkor zoom lenses hit their sharpness specs. The Toyota Prius hybrid battery pack ran on LaNi5 negative electrodes for two decades before lithium-ion took over — every one of those packs started life as kilograms of La2O3.
Common Uses
- La-exchanged zeolite Y catalyst for fluid catalytic cracking at 14 Mb/d crude
- LaNi5-based negative electrodes in nickel-metal-hydride rechargeable batteries
- High-index optical glass for camera lenses and telescope optics
- Solid-oxide-fuel-cell cathode (LaMnO3, LaCoO3) precursor
- Precursor for lanthanum-metal production via molten LaCl3/LaF3 electrolysis
- Phosphor matrix in tri-band fluorescent lamps (LaPO4:Ce,Tb green emission)
- Reference material in inductively-coupled-plasma rare-earth analysis
Safety Information
GHS classifications: H315 (skin irritation Cat 2), H319 (eye irritation Cat 2A), H335 (respiratory irritation). Acute oral LD50 in rats >5000 mg/kg — low acute toxicity. The chronic concern is pulmonary fibrosis from repeated inhalation of fine rare-earth oxide dust, documented in arc-light carbon-rod workers in the 20th century (rare-earth pneumoconiosis or 'cer pneumoconiosis'). OSHA has no specific PEL for La compounds; defer to general dust limits of 10 mg/m3 (total) and 5 mg/m3 (respirable). Use a P100 respirator for any operation generating airborne powder, and HEPA-filter all calcination off-gas paths.
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.