Reddish-orange Eu3+-doped sol-gel emitters based on LaF3 nanocrystals - Synthesis, structural and photoluminescence investigations
In this work, Eu3+-doped glass-ceramic materials containing LaF3 nanocrystals (GC Eu3+:LaF3) were fabricated by controlled heat-treatment of precursor xerogels synthesized via low-temperature sol-gel method. In order to characterize the thermal resistance of silica xerogels and to determine the crystallization temperature of LaF3 phase the TG/DSC analysis was performed. The formation of LaF3 nanocrystals in glass-ceramics was confirmed by X-ray diffraction measurements (XRD) and high-resolution transmission electron microscopy (HRTEM). In addition, the IR-ATR spectra were registered to identify the types of vibrational modes existing within prepared sol-gel hosts. The photoluminescence behavior of synthesized Eu3+-doped materials was characterized based on PLE (λem = 611 nm) and PL spectra (λexc = 393 nm) as well as luminescence decay analysis. The characteristic 5D0 → 7FJ (J = 0-4) intra-configurational transitions within 4f6 manifold of Eu3+ ions were registered in reddish-orange spectral range. In order to estimate the symmetry in local framework around Eu3+ ions the R/O-factor defined as I(5D0 → 7F2)/I(5D0 → 7F1) was calculated. The recorded decay curve for GC Eu3+:LaF3 exhibits bi-exponential profile, what provides the distribution of Eu3+ ions between two local sites with different decay rates.