Lanthanum oxychloride (LaOCl) is an inorganic compound belonging to the family of lanthanide oxyhalides. It consists of lanthanum, oxygen, and chlorine, typically forming a crystalline solid with a layered structure. The compound often appears as a white powder or crystalline material and is known for its thermal and chemical stability.
This material has important applications in optics, electronics, and catalysis. Due to its luminescent properties, doped LaOCl is widely used as a host material for phosphors, particularly in X-ray imaging screens and fluorescent lamps. When activated with rare-earth ions such as europium or terbium, it exhibits strong and efficient emission, making it valuable in lighting and display technologies.
Properties
LaOCl decomposes to La2O3 at about 700 °C in static air. The compound forms crystals of tetragonal system, space group P4/nmm.
- Chemical formula: LaOCl
- Molar mass: 190.35 g/mol
- Appearance: crystals
- Crystal structure: Tetragonal, layered structure similar to PbFCl-type compounds.
- Solubility: Slightly soluble in water, more soluble in strong acids; hydrolyzes slowly in moist air.
- Thermal stability: Stable at room temperature; decomposes at high temperatures to lanthanum oxide (La₂O₃) with release of chlorine.
- Magnetic/Electronic properties: Non-magnetic, wide bandgap material; has been investigated for optical and luminescent applications.
Synthesis
Lanthanum oxychloride is usually synthesized by heating lanthanum chloride (LaCl₃) in the presence of oxygen or by partial hydrolysis of lanthanum chloride at elevated temperatures. It crystallizes in a tetragonal structure, where alternating layers of lanthanum-oxygen and chlorine contribute to its anisotropic properties.
LaOCl can be synthesized by dissolving La2O3 in hydrochloric acid and vaporizing the water and then heating the precipitates. Also it can be formed by reacting LaCl3 with water:
LaCl3 + H2O → LaOCl + 2HCl
Occurrences and Applications
Lanthanum oxychloride is not found naturally but is a synthetic compound derived from lanthanum-bearing minerals such as monazite and bastnäsite, which are processed to extract lanthanum.
In laboratories and industries, it is prepared during the purification and intermediate stages of lanthanum salts. It is used in luminescent materials, phosphors, and as a precursor for other lanthanum-based oxides and catalysts.
