Abstract
Synthetic procedures to obtain size and shape-controlled microparticles hold great promise to achieve structural control on the microscale of macroscopic ceramic- or composite-materials. Lutetium oxide is a material relevant for scintillation due to its high density and the possibility to dope with rare earth emitter ions. However, rare earth sesquioxides are challenging to synthesise using bottom-up methods. Therefore, calcination represents an interesting approach to transform lutetium-based particles to corresponding sesquioxides. Here, the controlled solvothermal synthesis of size-tuneable europium doped Lu(OH)2Cl microplatelets and their heat-induced transformation to Eu:Lu2O3 above 800 °C are described. The particles obtained in microwave solvothermal conditions, and their thermal evolution were studied using powder X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical microscopy, thermogravimetric analysis (TGA), luminescence spectroscopy (PL/PLE) and infrared spectroscopy (ATR-IR). The successful transformation of Eu:Lu(OH)2Cl particles into polycrystalline Eu:Lu2O3 microparticles is reported, together with the detailed analysis of their initial and final morphology.
Highlights
Luminescent micro- or nanoparticles of wide band gap semiconductors are interesting building blocks for innovative functional materials with macroscopic dimensions, for example for optical ceramics [1,2,3,4]
The product stoichiometry was further confirmed by microelemental analysis on the obtained powders, which showed a ratio of carbon (0.09), chlorine (1.0) and hydrogen (2.4) with respect to Lutetium (1.0)
Longer reaction times at lower temperature (150 ◦ C, 60 min) further reduced the particle size to 260 ± 10 nm in length, 120 ± 5 nm in width, and thicknesses in the range 10–40 nm (Figure 1a–c). These findings revealed that higher reaction temperatures and shorter reaction times led to larger particles
Summary
Luminescent micro- or nanoparticles of wide band gap semiconductors are interesting building blocks for innovative functional materials with macroscopic dimensions, for example for optical ceramics [1,2,3,4]. When functional micro- or nanomaterials are assembled without dispersing hosts, optical grade polycrystalline ceramics and composites for scintillation detection may be obtained, e.g., by using radioluminescent microparticles as building blocks [2,3,11,12] In this scenario, doped rare earth sesquioxides (RE2 O3 ) are appealing materials for phosphor or scintillation applications where light transmission is required, due to their wide band gap. Lu2 O3 has a band gap of around 5.8 eV, well above the visible range, and it is an ideal host for optically active rare earth dopants as it allows for substitutional doping which leads to bright radioluminescence [1,6,13,14,15]
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