Erbium oxychloride (ErOCl) is an inorganic compound containing erbium, oxygen, and chlorine. It belongs to the family of rare-earth oxyhalides, typically formed by the controlled hydrolysis of erbium trichloride (ErCl₃) or through reactions involving erbium oxides and chlorinating agents. This compound crystallizes in a layered structure where erbium cations are coordinated by both oxide and chloride anions, giving it unique optical and electronic properties.
ErOCl appears as a crystalline solid, often pink to violet in color due to the characteristic f–f electronic transitions of the trivalent erbium ion (Er³⁺). It is sparingly soluble in water but can hydrolyze to produce erbium hydroxide and hydrochloric acid. Like other rare-earth oxyhalides, it demonstrates high thermal stability and is resistant to decomposition under moderate heating, though it may convert to erbium oxide at elevated temperatures.
Synthesis
The compound can be obtained by reacting Er2O3 solution with fused magnesium chloride.
Physical properties
The compound forms crystals of the tetragonal system, space group P4/nmm.
- Chemical formula: ErOCl
- Appearance: crystals
- Crystal structure: Tetragonal (layered oxyhalide type structure, similar to other LnOCl compounds).
- Solubility: Sparingly soluble in water; hydrolyzes slowly, especially in moist air, forming hydroxides and chlorides.
- Thermal stability: Stable at moderate temperatures but decomposes at higher temperatures into erbium oxide (Er₂O₃) and hydrogen chloride when exposed to moisture.
- Magnetic/optical properties: Shows paramagnetism due to unpaired 4f electrons and exhibits sharp f–f optical transitions, useful in spectroscopy and laser materials.
Occurrences
- Erbium oxychloride does not occur naturally; it is a synthetic compound. It is generally prepared in laboratories by controlled hydrolysis of erbium trichloride (ErCl₃) or by heating erbium chloride in the presence of oxygen or water vapor.
- Related oxychlorides exist for many lanthanides, often produced as intermediates in high-temperature chlorination or oxide–halide reactions.
- It finds use in optical materials, phosphors, and research into erbium-doped systems because erbium ions are important for infrared emission (notably at ~1.55 μm, used in telecommunications).
Applications
The material has applications in optics and photonics, as erbium ions are valuable for their strong luminescence in the infrared region, particularly around 1.55 µm, important for fiber-optic communication. Erbium oxychloride can serve as an intermediate in the preparation of pure erbium oxide, glasses, ceramics, and phosphors. Its stability, combined with erbium’s unique spectroscopic features, makes ErOCl a useful compound in advanced material research.
