2007

Zirconia Based Nanomaterials for Oxygen Sensors – Generation, Characterisation and Optical Properties

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Janusz D. Fidelus, Witold Lojkowski, Donats Millers,
Larisa Grigorjeva, Krishjanis Smits and Robert R. Piticescu

Abstract: Microwave driven hydrothermal synthesis and hydrothermal synthesis were used to
obtain ZrO2 nanopowders. Their production with varying phase composition, the characterisation
and selected optical properties concerning their potential use as luminescence oxygen sensors are
reported. It was found that the powders obtained by the microwave driven hydrothermal method
and annealed at 750 0C in air show experiment repeatability within an accuracy of 6 %.

Solid State Phenomena Vol. 128 (2007) pp. 141-150

© (2007) Trans Tech Publications, Switzerland

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Comparison of ZrO2:Y Nanocrystals and Macroscopic Single Crystal Luminescence

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Krisjanis Smits, Donats Millers, Larisa Grigorjeva, Janusz D. Fidelus, Witold Lojkowski

Abstract. The luminescence spectra of a tetragonally structured ZrO2:Y single crystal and
nanocrystals were compared. It was found that the number of luminescence centers contributed
to the spectra. The excitation of luminescence within the band gap region led to different
luminescence spectra for the single crystal and nanocrystal samples, whereas recombinative
luminescence spectra were the same for both samples. The origin of this difference is that in
the nanocrystals, even under excitation within the band gap, charge carriers were created.
Zirconium- oxygen complexes distorted by intrinsic defects were proposed to be the
luminescence centres responsible for the wide luminescence band observed.

Journal of Physics: Conference Series 93 (2007) 012035

doi:10.1088/1742-6596/93/1/012035

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The Luminescence Properties of ZnO nanopowders

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Aleksandr Kalinko, Janusz D. Fidelus, Larisa Grigorjeva, Donats Millers, Claude J. Monty, Adam Presz and Krisjanis Smits

Abstract. Pure and Al3+ doped ZnO nanopowders were studied by means of time-resolved
luminescence spectroscopy. The powders were synthesized by hydrothermal and plasma
methods. These powders were used as a raw material for vaporization-condensation process
inside the Solar reactor. The commercially available ZnO nanopowder was studied for a
comparison. Exciton to defect band luminescence intensity ratio was estimated in different
types of ZnO nanopowders. It was found that nanopowders with whiskers morphology show
superlinear luminescence intensity depending on excitation density. The observed effect
depends on the average nanoparticle size and on the powder morphology.

IOP Publishing
Journal of Physics: Conference Series 93 (2007) 012044

doi:10.1088/1742-6596/93/1/012044

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The Luminescence Properties of ZnO:Al Nanopowders Obtained by Sol-gel, Plasma and Vaporization-condensation Methods

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Larisa Grigorjeva, Donats Millers, Krishjanis Smits, Claude Monty, Jules Kouam and Lassad El Mir

Abstract: ZnO nanocrystals were synthesized and characterized by XRD and SEM methods. The
luminescence spectra and decay kinetics were studied under pulsed laser excitation (266 nm, 8 ns).
ZnO and ZnO:Al powders were prepared by sol-gel and plasma chemical synthesis. These powders
were used as a raw material for the SPVD (Solar Physical Vapour Deposition) process. In this way,
the vaporisation-condensation phenomenon (VC) led to the formation of ZnO whiskers and
nanopowders. The luminescence properties of the VC nanopowders were studied and compared to
those displayed by the raw material. The Al dopant, present in the raw powders as a solid solution
and ZnAl2O4 precipitates, was only present as Al ions in the nanopowders after the SPVD. The blue
luminescence intensity increased considerably after SPVD. The whiskers type microstructures
showed nonlinear blue luminescence dependent on the excitation pulse density.

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Luminescence of oxygen related defects in zirconia nanocrystals

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K. Smits, L. Grigorjeva, W. Łojkowski, and J. D. Fidelus

The luminescence of undoped tetragonal structure ZrO2 nanocrystals was studied. The luminescence intensity
depends on oxygen content in gases mixture in which the nanocrystals were annealed. The distorted
Zr-O bond is suggested to be the recombination center for band carriers. The oxygen deficient defect
is proposed to be responsible for photoluminescence.

Physica Status Solidi (C) Current Topics in Solid State Physics 4, No. 3, 770– 773 (2007)

DOI 10.1002/pssc.200673850

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