Particle Size and Crystal Phase Dependent Photoluminescence of La₂Zr₂O₇:Eu³⁺ Nanoparticles

Herein, La₂Zr₂O₇:5% Eu³⁺ nanoparticles (NPs) with different sizes have been synthesized for the first time through a modified facile molten salt process using a single-source complex precursor of La(OH)₃·ZrO(OH)₂:Eu(OH)₃·nH₂O. It was found that the concentration of the added ammonia to co-precipitate the corresponding metallic ions to form the precursor can influence the final particle size of the fluorite La₂Zr₂O₇:5%Eu³⁺ NPs. Furthermore, the crystal phase of the La₂Zr₂O₇:5%Eu³⁺ NPs was transferred from fluorite to pyrochlore after thermal treatment at 1000°C. The relationship between photoluminescence (PL), quantum yield (QY), particles size and crystal phase has been further investigated through fluorescence decay, site symmetry, and Judd-Ofelt (J-O) analysis. Specifically, PLQY and lifetime increase with increasing particle size of the fluorite La₂Zr₂O₇:5%Eu³⁺ NPs. Additionally, crystal phase transfer from fluorite to pyrochlore resulted in large PLQY decrease and moderate lifetime increase in the La₂Zr₂O₇:5%Eu³⁺ NPs.