Hafnium oxide sol-gel material with embedded luminescent polyol nanoparticles M.-A.
1 Flores-González ,
P.-N.
1 Olvera-Venegas ,
M.-A. Hernández-Pérez2, R. González-Montes de Oca1, 1 M. Villanueva-Ibáñez
1Polytechnique
University of Pachuca/ Hidalgo, México 2I National Polytechnic Institute / México, D.F. flores@upp.edu.mx
Hafnium dioxide (HfO2)-based materials can be used in diverse applications; yttrium oxide stabilized hafnium oxide is widely employed in high temperature applications, anticorrosion, thermal barrier or optical coatings. Furthermore, HfO2 presents a high crystalline density (≈10) that makes it attractive for host lattice activated by rare earths for luminescent applications [1]. In this work, Y2O3:Eu3+ nanoparticles (NPs) embedded in HfO2 were prepared by polyol and sol-gel techniques, respectively. The structure and growth behavior of nanoparticles in the sol-gel powders were studied by X-ray diffraction, dynamic light scattering, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and micro Raman spectroscopy. The experiments indicate that NPs have a polycrystalline structure with average size between 20 to 50 nm. The photoluminescent (PL) characteristics of nanostructured material were investigated.
RESULTS
EXPERIMENTAL 1) Polyol synthesis of Y2O3Eu3+ nanoparticles
B)
(0,3,2)
(-1,1,2)
(3,1,0)
(0,2,2)
(1,1,1)
A)
A)
(-1,1,1)
B)
(1,1,0)
All the polyol samples were structurally characterized assynthesized.
Intensity (a.u.)
Polyol method is a direct precipitation of oxides in a high boiling alcohol to obtain aggregates of NP’s or colloidal NP’s
Characterization of HfO2 sol-gel precursor and Y2O3Eu3+ nanoparticles
Wavenumber
10
20
30
40
50
60
70
2- degree
2) Sol-gel synthesis of HfO2 and Y2O3Eu3+ nanoparticles Hf(OC2H5)4 (1 mol)
A) Infrared spectra evolution of HfO2 sol-gel solution heat-treated at different temperatures. (B) XRD of HfO2 annealed at 700ºC with monoclinic structure.
A) Electron diffraction pattern of as-synthesized with cubic crystalline structure. B) EDS spectrum of the as-synthesized ultra fine powder
C5H8O2 (acac) (1 mol)
C2H5OH stirred 1 h at 90 °C in N2 atmosphere
Characterization of HfO2/Y2O3Eu3+
C2H5OH
1600000
mixing
3+ HfO2/Y2O3:Eu
1400000
Hydrolysis under atmosphere saturated with water
Intensity (CPS)
500°C
3+
HfO2/Y2O3:Eu 5%
Intensity (a.u.)
Stirred at 100 °C 2 h in N2 atmosphere (~2% RH)
700°C
5
D0
7
F2
1200000
1000000
800000
600000
Y2O3Eu3+ nanoparticles
HfO2
400000
HfO2 sol-gel solution
550
200
300
400
500
600
700
600
650
700
Wavelength (nm)
-1
drying powders
CONCLUSION This work shows that HfO2/Y2O3:Eu3+ can be prepared at low temperature (<200ºC. Polyol method and sol-gel process can be combined to result in new materials with different properties. HfO2/Y2O3:Eu3+ heat treated at 700ºC shows a monoclinic structure and an homogeneous morphology in sub-micrometric size conformed by smaller nanostructures than 50 nm. Preliminary luminescent tests indicated that the obtained materials have the characteristic 5D0 7F2 transition of Eu3+ ions
Raman shift (cm )
:Eu3+
Raman spectra of HfO2/Y2O3 heat-treated at 500 and 700ºC, and HfO2 sol-gel heat-treated at 700ºC. The low content of Y2O3:Eu3+nanoparticles does not influence the crystal structure of monoclinic HfO2.
SEM image of 700°C heat-treated powders. The figure shows HfO2/Y2O3:Eu3+ aggregates conformed of smaller structures on the order of 20 to 50 nm.
Room temperature emission spectra of powders heattreated at 700°C (lexc= 252nm). Transition 5D0 7F2 confirms the location of Eu 3+ ions in Y2O3 embedded in a HfO2 matrix.
REFERENCES [1] C. LeLuyer, M. Villanueva-Ibañez, A. Pillonnet, and C. Dujardin; (2008), HfO2:X (X ) Eu3+, Ce3+, Y3+) Sol Gel Powders for Ultradense Scintillating Materials. J. Phys. Chem. A , 112, 10152–10155. [2] M.A. Flores-Gonzalez, K. Lebbou, , R. Bazzi, C. Louis, P. Perriat, O. Tillement; (2005), Eu3+ addition effect on the stability and crystallinity of fiber single crystal and nanostructured Y2O3 oxide. Journal of Crystal Growth 277, 502–508.
Acknowledgements The authors acknowledge CONACyT support.