Synthesis and White Light Emission of Rare Earth‐Doped HfO₂ Nanotubes

Abstract

Luminescent nanotubes based on rare earth (RE) (Eu, Tb)‐doped hafnia (HfO2) were prepared by radio frequency (RF) sputtering with electrospun polyvinylpyrolidone (PVP) nanofibers as templates. The nanotubes annealed at 500°C have a uniform structure with desired tubular morphologies. Various colors of photoluminescence (PL) could be easily obtained by tuning the concentrations of the RE ions in the HfO2 host. The Eu‐ and Tb‐codoped HfO2 (HfO2:Eu&Tb) nanotubes exhibited white light emissions under a 325 nm excitation. Good Commission International de I'Eclairage (CIE) coordinates (0.333, 0.323) and color temperature (Tc) (5465 K) were achieved in the HfO2:Eu&Tb nanotubes. Experimental evidence showed that the presence of blue emission originates from the defect states in HfO2 nanotubes, the green and the red emissions can be attributed to the inner 4f shell transitions of corresponding Tb3+ ions and Eu3+ ions in HfO2 shells, respectively. Compared with RE‐doped HfO2 films, the nanotube samples showed intense white light emissions, revealing that the HfO2:Eu&Tb nanotubes are an efficient white light‐emission material.

Investigation on cation distribution and luminescence in spinel phase γ-Ga3−δO4 : Sm nanostructures using X-ray absorption spectroscopy

“…It is visible from the CIE colour chromaticity diagram that the pure g-Ga 2.67 O 4 nanoparticle sample exhibits DAP induced cyangreen emission characteristics (CIE coordinates, 0.26, 0.43) while the Ga 2 O 3 _600 (CIE coordinates, 0.36, 0.45) or Ga 2 O 3 _900 (CIE coordinates, 0.37, 0.46) samples exhibits green yellow emission which is analogous to the previous reports where the increase of particle size had demonstrated the red-shied PL bands. 60,61 By considering the standard CIE coordinates for the white light (i.e., 0.333, 0.333), 66 we can state that the Sm doped g-Ga 2.67 O 4 nanoparticles have shown a nearly white line emission, i.e., ranging from violet-blue to orange-red emission. The CIE coordinates for the g-Ga 2.67 O 4 : 5Sm and g-Ga 2.67 O 4 : 10Sm samples are (0.28, 0.34) and (0.30, 0.35), respectively.…”

Spray Pyrolysis Technique; High-K Dielectric Films and Luminescent Materials: A Review

“…[37,38]. They have been synthesized through a variety of physical and chemical techniques, including: Hidrothermal/Solvothermal [39,40,41], solid-state reaction [42], sol-gel [43,44], laser ablation [45,46], sputtering [47], Pechini Method [48], plasma electrolitic oxidation [49], conventional melt-quenching method [50,51], combustion synthesis [52], solvent evaporation method [53,54,55], and co-precipitation process [56]. Among these techniques, spray pyrolysis began to be used for this purpose in the mid-1980s, and it is still used today [57,58]—proving to be a practical, low cost, easy to extrapolate for large area deposition technique.…”

Phase Control in Hafnia: New Synthesis Approach and Convergence of Average and Local Structure Properties

“…10 Though much less studied than the ZrO 2 homologue, several reports evidenced remarkable photoluminescence (PL) and scintillator properties of monoclinic and tetragonal/cubic phases of HfO 2 when doped with lanthanide (Ln) ions such as Ce, Sm, Eu, Tb, and Dy. 5−7,12−15 As Zr and Hf are regarded as the two chemically most similar homogenesis elements, 16 HfO 2 and ZrO 2 are called twin oxides 17,18 because of their similar crystal structure, with close ionic radii of 0.78 Å (Hf 4+ ) and 0.79 Å (Zr 4+ ), 19 despite their large difference in the atomic number, Z, 72 to 40, respectively. In the bulk, hafnia and zirconia can each adopt three different, albeit related, crystal structures at ambient pressures, that is, monoclinic, tetragonal, and cubic.…”