In recent decades, rare earth (RE 3+ ) ion-doped luminescent nanomaterials have garnered startling interest and are stimulated by their continuously expanding need in nanotechnology, optoelectronics, and biomedicine [1][2][3][4][5][6]. However, due to their thermal quenching at higher temperatures, their application in specific fields is greatly limited [7]. This research aims to develop negative thermal expansion (NTE) luminescent materials in applications such as aerospace technology, electronics, fuel cells, thermal sensors, automotive, and manufacturing industries. The NTE is an unusual physicochemical process in which the material contracts upon heating rather than expanding [8]. The most well-known material with NTE is water at 0-3.98 °C. Thus, designing and developing NTE materials and studying their behavior with temperature is crucial to developing better-performing materials. To this end, the current work focuses on designing and developing RE ion-doped YF 3 nanoparticles.

The triple ion (Eu 3+ /Sm 3+ /Tb 3+ ) co-doped YF 3 nanoparticles were synthesized, followed by a simple one-step hydrothermal synthesis at 180 °C for 10 h in a conventional oven [9]. The structure and phase purity of the as-synthesized nanomaterials were confirmed using X-ray diffraction (XRD). The sharp diffraction peaks indicate a perfect orthorhombic crystalline structure of YF 3 with a Pnma space group. All the diffraction peaks by the YF 3 Waimirite crystal structure. Scanning electron microscopy (SEM) images confirmed the as-synthesized material morphology. The particles are in an orthorhombic shape.

The energy-dispersive spectroscopy (EDS) analysis of the prepared material (in Figure 1) reveals the elemental distribution. EDS detected traces of yttrium and fluorine ions along with the three co-dopants terbium, samarium, and europium. The elemental composition analysis by the EDS technique confirms that the successful doping of RE ions into the YF 3 lattice.

The excitation and emission fluorescence spectra were measured for the as-prepared nanoparticles at room temperature. The emission spectrum was recorded under the 590 nm excitation, reveals the Eu 3+ blue emission corresponds to the 5 D 3 → 7 F n (n=1 -3) transitions, compared with literature results [10]. On the other hand, the excitation spectra were recorded by monitoring the Eu 3+ ion emission peak located at 254 nm and the Tb 3+ ion mission peak situated at 373 nm (Figure 2). The excitation spectra show prominent peaks corresponding to Eu 3+ and Tb 3+ ions occurring from their 7 F n (n=1-3) electronic energy state. A detailed study of the energy transfer mechanism between the RE 3+ ions was investigated. The temperature-dependent emission properties were also recorded. The nanoparticles were further tested as NTE materials, which can be implemented in various applications to advance technological benefits [11]. Microscopy and Microanalysis, 31 (7), 2025, 1859-1860 https://doi.org/10.1093/mam/ozaf048.941 Proceedings Downloaded from https://academic.oup.com/mam/article/31/Supplement_1/ozaf048.941/8212518 by guest on 26 July 2025