Hexagonally ordered KLaF4 host: phase-controlled synthesis and luminescence studies

Area of Science:

• Materials Science
• Inorganic Chemistry
• Solid-State Chemistry

Background:

• Potassium lanthanum fluoride (KLaF(4)) is a material with potential applications in optics and photonics.
• Controlling the crystalline phase and properties of KLaF(4) is crucial for optimizing its performance.
• Previous synthesis methods may have limitations in achieving specific polymorphs or desired properties.

Purpose of the Study:

• To report the first successful synthesis of hexagonally ordered KLaF(4).
• To investigate the influence of different lanthanum precursors and reaction conditions on KLaF(4) phase formation.
• To explore the optical properties of hexagonal KLaF(4), particularly when doped with erbium (Er(3+)).

Main Methods:

• Synthesis of KLaF(4) using three different lanthanum precursors (La(O(i)Pr)(3), La(acac)(3), LaCl(3)) and potassium fluoride (KF).
• Reactions conducted under nonaqueous conditions and atmospheric pressure.
• Characterization using powder X-ray diffraction (PXRD) with Rietveld refinement, Raman spectroscopy, diffuse reflectance, and emission studies.

Main Results:

• Successful synthesis of hexagonally ordered KLaF(4) was achieved for the first time.
• Hexagonal KLaF(4) was formed using La(O(i)Pr)(3) and La(acac)(3) with KF in methanol at 65 °C, while LaCl(3) yielded cubic KLaF(4) at room temperature.
• Hexagonal KLaF(4) exhibits a lower effective phonon energy (262 cm(-1)) and strong green emission upon excitation when doped with 3 mol% Er(3+).
• A transparent polymer composite containing hexagonal KLaF(4):Er(3+) phosphor was demonstrated.

Conclusions:

• The synthesis of hexagonally ordered KLaF(4) is feasible and dependent on precursor choice and reaction conditions.
• Hexagonal KLaF(4) possesses favorable characteristics, including low phonon energy, making it a promising host for optical applications.
• The Er(3+)-doped hexagonal KLaF(4) exhibits efficient upconversion luminescence, suitable for light-emitting devices and phosphors.