Kinetics or thermodynamics? Extolling their role to modulate the crystal phases and luminescence of KY3F10:Eu3+ powders

Abstract

KY₃F₁₀, a fluoride compound with two polymorphs (α and δ), has been a subject of study due to its unique properties. Obtaining the metastable δ-phase has been challenging, but this study presents an enhanced synthetic methodology using coprecipitation to isolate specific crystal phases. Varying the reaction temperature and time allows for the modulation of polymorph formation. The structural analysis of the synthesized powders reveals the influence of kinetic and thermodynamic control. The morphology of the particles is also affected by these factors, with different reaction conditions leading to distinct particle shapes. The luminescent response of Eu³⁺-doped powders helps understand the structural stability. It is demonstrated that time-resolved fluorescence spectroscopy is a sensitive and direct measurement to follow the observed changes. Overall, this study demonstrates the interplay between thermodynamics and kinetics in materials synthesis and the impact on crystal phase formation and properties.