Low-temperature formation of cubic β-PbF2: precursor-based synthesis and first-principles phase stability study

Area of Science:

• Solid-state chemistry
• Materials science
• Inorganic chemistry

Background:

• Lead(II) fluoride (PbF(2)) exists in two main polymorphs: orthorhombic α-PbF(2) and cubic β-PbF(2).
• The cubic β-PbF(2) phase is typically stable only at high temperatures, requiring significant energy for its formation.
• Understanding the synthesis and phase stability of PbF(2) polymorphs is crucial for potential applications in optics and electronics.

Purpose of the Study:

• To develop a novel precursor-based synthesis route for the cubic β-PbF(2) phase.
• To enable the preparation of β-PbF(2) at temperatures significantly below its usual transition point.
• To investigate the relative thermodynamic stability of the α- and β-phases of PbF(2) under accessible conditions.

Main Methods:

• Synthesis of β-PbF(2) using molecular precursors: Pb[Se(C(6)H(2)(CF(3))(3))](2) and Pb(C(6)H(2)(CF(3))(3))(2).
• Characterization of the resulting PbF(2) material, including macroscopic crystals and nanoparticulate powder.
• Theoretical investigation using Kohn-Sham density functional theory (DFT) to calculate phase stability and energy differences.

Main Results:

• Successful synthesis of cubic β-PbF(2) at relatively low temperatures using the precursor method.
• The presence of short Pb-F contacts in the molecular precursors facilitates the formation of β-PbF(2).
• DFT calculations indicate that the β-phase has a slightly lower energy than the α-phase (0.5-1.7 kJ mol(-1)), suggesting its potential stability under certain conditions.

Conclusions:

• A novel and efficient precursor-based method allows for the low-temperature synthesis of cubic β-PbF(2).
• The findings suggest that the cubic β-phase may be more thermodynamically stable than previously assumed.
• This work opens avenues for exploring the properties and applications of β-PbF(2) synthesized under milder conditions.