An Uncommon Hypervalent Fluorooxosilicophosphate.

Area of Science:

• Materials Science
• Inorganic Chemistry
• Solid-State Chemistry

Background:

• Silicon's coordination diversity drives silicate structural richness.
• Hypervalent silicon species are rare, especially mixed-anion fluoroxosilicates.

Purpose of the Study:

• To synthesize and characterize novel mixed-anion hypervalent fluoroxosilicate compounds.
• To investigate the structural stability and ionic conductivity of the new material.

Main Methods:

• Synthesis of Na4Si2PO4F9
• Phonon dispersion calculations for structural stability
• Temperature-dependent conductivity measurements

Main Results:

• Successfully synthesized Na4Si2PO4F9 containing two unprecedented hypervalent silicon species (trans-SiO2F4 and SiOF5).
• Phonon calculations confirmed the structural stability of the compound.
• Achieved ionic conductivity of 4.0×10⁻⁵ S⋅cm⁻¹ at 700 K with low activation energy (53.1 KJ⋅mol⁻¹).

Conclusions:

• This work expands the structural chemistry of silicates by introducing new hypervalent silicon species.
• Na4Si2PO4F9 is a promising candidate for solid ionic conductors in battery technologies.