A new layered perovskite, KSrNb2O6F, by powder neutron diffraction

Area of Science:

• Solid-state chemistry
• Inorganic materials science
• Crystallography

Background:

• Layered oxyfluorides represent a significant class of inorganic materials with diverse structural motifs.
• The Dion-Jacobson family of compounds, characterized by the general formula A[A'(n-1)B(n)X(3n+1)], features layered perovskite structures.
• Understanding the precise atomic arrangement in novel layered compounds is crucial for predicting their properties.

Purpose of the Study:

• To determine the crystal structure of the newly synthesized layered oxyfluoride, potassium strontium diniobium hexaoxide fluoride (KSrNb(2)O(6)F).
• To investigate the structural characteristics, including distortions and atomic ordering, within the perovskite slabs.
• To classify the compound within the established Dion-Jacobson family based on its structural parameters.

Main Methods:

• Powder neutron diffraction was employed to collect structural data.
• The crystal structure was refined in the orthorhombic space group Immm.
• Bond-valence-sum calculations were utilized to assess oxygen/fluorine ordering.

Main Results:

• The crystal structure of KSrNb(2)O(6)F was successfully refined, confirming its layered nature with n=2 in the Dion-Jacobson family.
• The compound consists of double perovskite slabs, [SrNb(2)O(6)F](-), interleaved with K(+) ions.
• Significant distortions and tilting of NbO(5)F octahedra were observed along the a axis, and evidence for O/F ordering along the b axis was found.

Conclusions:

• KSrNb(2)O(6)F represents a new member of the Dion-Jacobson layered perovskite family.
• The refined structure reveals specific atomic ordering of oxygen and fluorine within the distorted NbO(5)F octahedra.
• The detailed structural characterization provides a foundation for exploring the physical and chemical properties of this oxyfluoride material.