Rietveld refinement of Sr(5)(AsO(4))(3)Cl from high-resolution synchrotron data

Area of Science:

• Solid-state chemistry
• Crystallography
• Materials science

Background:

• Apatite-type compounds are known for their diverse applications.
• Halogenoapatites with the general formula A(5)(YO(4))(3)X are a well-studied class of materials.
• Strontium-based apatites are of interest due to their unique properties.

Purpose of the Study:

• To synthesize and characterize the apatite-type compound penta-strontium tris-[arsenate(V)] chloride, Sr(5)(AsO(4))(3)Cl.
• To determine the crystal structure of the synthesized compound.
• To compare its structure with other known halogenoapatites.

Main Methods:

• High-temperature ion exchange reaction between a synthetic mimetite sample [Pb(5)(AsO(4))(3)Cl] and strontium carbonate (SrCO(3)).
• High-resolution synchrotron X-ray powder diffraction (XRPD) for data collection.
• Rietveld refinement for crystal structure determination.

Main Results:

• Successful synthesis of Sr(5)(AsO(4))(3)Cl with SrCO(3) as a by-product.
• The compound crystallizes in the apatite structure type, space group P6(3)/m, consistent with other halogenoapatites.
• Detailed structural analysis revealed two independent Sr(2+) cation sites and isolated tetrahedral AsO(4)(3-) anions, with chloride anions located in the structure's channels.

Conclusions:

• The synthesized strontium chloride apatite, Sr(5)(AsO(4))(3)Cl, adopts the characteristic apatite structure.
• The crystal structure is analogous to other halogenoapatites, confirming the general formula A(5)(YO(4))(3)X.
• The study provides a detailed crystallographic description of this strontium-based apatite compound.