Elaboration of micro-dimensional optical oxide materials from
the Ti, Zr and Hf alkoxides
Valter Reedo1,2, Martin Järvekülg1,2, A. Lukner1 , K. Keevend1, A. Lõhmus1, U. Mäeorg2
1Institute of Physics, University of Tartu, Riia 142, EE-51014 Tartu, Estonia,
2Institute of Organic and Bioorganic Chemistry, University of Tartu, Jakobi 2, 51014 Tartu, Estonia
INTRODUCTION
Nano- and microscale structures have exceptional properties and have
great potential as the building blocks of nano- and microdevices systems of
high efficiency.
In present work we report preparation of nano-dimensional ZrO2, TiO2
and HfO2 rare earth doped and un-doped thin films, fibres, powders and
micro-structured surfaces. These rare earth doped oxides are valuable sensors
(e.g. for monitoring of ambient gas content at high temperatures or for
detection of high energy particles).
We observed, for the first time, the self formation of ZrO2, TiO2 and
HfO2 micro-tubes from precursor solution. We also work on in-situ conversion
of prepared oxide materials to metal carbides for elaboration of new approach
for obtaining of hard alloys.
THIN FILMS BY DIP-COATING AN D SPIN-COATING
Prepared films were smooth and
~50 nm in thickness. The
morphology of spin-coated Sm3+
doped and undoped films (fig 1.)
show that formed crystallites are
different in size (20-30 nm for
doped and 90-120 nm for
undoped films). This indicates
that growth of nano-crystallites is
influenced by addition of dopant
in TiO2 materials.
AIM OF THE WORK
• Elabortion of method for preparation of rare earth doped and un-doped thin
films, fibres, powders and micro-structured surfaces starting from the Zr, Ti,
Hf alkoxides.
• Finding novel methods for manipulation of viscose alkoxide polymer to
develop new micro-dimensional structures.
• Characterization of obtained low-dimensional oxide structures for finding
new properties and fenomenons.
FIBERS BY ROAD BULLING
Fibers were prepared by glass road spinning
technique from solvent free precursors.
Prepared HfO2, ZrO2 and TiO2 fibers were 50100μm in diameter. Luminescence spectrum was
measured for Sm3+ doped TiO2 fibers (Fig 6.).
Figure 1. AFM image of a) Sm3+ doped
TiO2 b) undoped TiO2.
INTRODUCTION OF SOL-GEL TECHNIQUE
Relatively simple and low-cost sol-gel technique
was used for preparation of low-dimensional
ZrO2, TiO2 and HfO2 undoped and rare earth
doped oxide materials. Below is brought a brief
overview of this technique.
Water, dopant
Alkoxides
In collaboration with S. Slange
and A. Lukner we have
observed gas-sensing property
on Sm3+ doped spin-coated and
dip-coated TiO2 thin film (fig
2.). This makes this material
potentially valuable for gas
sensing applications.
Figure 2. The PL intensity responses of Smdoped TiO2 powders for different oxygen
concentrations in ambient atmosphere
POWDERS BY RAPID HYDROLYSIS
AND CONDENSATION
+ Water
Precursor
stadium
(viscose material)
In collaboration with A.
Lukner we have observed
different behavior of
Sm3+
spectra intensity by heat
treatment for TiO2 thin films
and powdwes (fig 4.). This
gives us tool for manipulation
of
photoluminescence
properties of material.
Hydrolysis,
Polymerization
Figure 6. Photoluminescence of
Sm3+ doped TiO2 fiber.
Controlled
gelation and
hydrolysis
Figure 7. Photos of
hafnia fibers
Figure 5. SEM image of
Sm3+ doped TiO2 powder.
MICRO-STRUCTURED OXIDE SURFACES
Micro-structured HfO2 surfaces (Fig 8.)
were prepared by sol-gel molding technique [1].
50 μm
Figure 8. Micro-structured HfO2 surfaces.
CONCLUSIONS
• Sol-gel method can be applied for elaborating various
low-dimentional TiO2, ZrO2 and HfO2 samples.
• Fibers, films and micro molded surfaces are
transparent and the material is suitable for hosting rareearth dopants, which make them potentially valuable for
different optical uses.
•A novel method for manufacturing micro- and possibly
nanoscale tubes and fibers was found. Further studies
are underway to clarify cognitive
aspect of the
materials and to determine there industrial potential.
Figure 6. Self formed zirconia microtubes.
REFERENCES
[1] T. M. Gale, C. Grimkiewicz, S. Obi, M.
Schniper, J. Söchtig, H. Thiele, S. Westenhöfer,
Optics and Lasers in Engineering 43 (2005) 373386.
[2] S. Hasegawa, Y. Sasaki and S. Matsuhara,
Sensors and Actuators, (1993) 509-510.
Figure 4. The
spectra intensity
change in post
preparation
annealing
for
films (B) and for
powders (C)
SELF-FORMATION OF OXIDE
MICRO-TUBES BY CONTROLLED
GELATION AND HYDROLYSIS.
Varying catalyst concentration
in the sol resulted in self-formation
of solid tubular low-dimensional
structures. Most of these were in the
form of tubes with ~1mm in length
and ~30-4 μm in diameter. Nanoscale
fiber-like solid particles could also
be detected.
AKNOWLEDGEMENTS
This work has been supported by
ETF6537, ETF6660, ETF6163,
SF0382149s02, Estonian
Nanotechnology Competence Center
and Doctoral school of material science
and material technology.