Luminescence of Nanosized ZrO2 and ZrO2: Pr Powders

Journal of Applied Physics, 2003

Embedding luminescent rare earth ions into transparent oxides such as ZnO is a well-known approach to functionalize the material by adding photon-management properties. In this paper we present a detailed study of the luminescence properties and energy level structure of Pr 3+ and Yb 3+ ions embedded in ZnO thin films deposited by magnetron reactive sputtering. Careful study of the photoluminescence and excitation spectra allowed identifying and locating almost all excited levels of Pr 3+ and Yb 3+ ions. Thus, an almost complete electronic energy level diagram of these ions in the ZnO crystal lattice can be drawn for the first time. In particular, we show that the crystal field of ZnO strongly modifies the energy level structure of the Pr 3+ and Yb 3+ ions creating energy mismatches between the transitions useful for cooperative down conversion. Finally, we demonstrate that light emission from Pr 3+ ions can be induced both by direct excitation of the ions and indirectly by energy transfer from the ZnO matrix.

Radiation Physics and Chemistry, 2011

a b s t r a c t Thermoluminescence (TL) and photoluminescence (PL) characteristics of CaSO 4 :Ce nanocrystalline prepared by hydrothermal method has been studied. Its TL glow curve contains three overlapping glow peaks at around 490, 505 and 521 K. Emission spectra band at 303 and 324 nm were observed for the orthorhombic phase of nanosheets. TL response of the prepared nanocrystalline to b and c radiation was studied and the sensitivity of the nanosheets was found much more than that of analogous microcrystalline and is around 10 times higher than the well known high sensitive TL dosimeter LiF:Mg, Cu, P (GR-200) hot-pressed chips. TL kinetic parameters of this nanocrystalline are also presented.

With the help of microwave-assisted technique, zirconia (ZrO 2) nanocrystalline powder was synthesized using a structure directing agent which could be controlled by the nucleation and particle growth. The various characterizations, namely, phase, surface morphology, surface area analysis and optical property were carried out by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) and UVevisible spectroscopy. From XRD analysis, it was found that the synthesized materials reveal the tetragonal crystalline phase. The average particle size of ZrO 2 was found 14.7 nm by TEM. Specific surface area, pore volume and the pore size for ZrO 2 are 220 m 2 /g, 0.02 cm 3 /g and 10.7 nm investigated by BET, respectively. UVevis DRS spectra of the prepared material confirmed that the Zr atoms are exclusively incorporated within silica framework. Besides, the maximum absorption peaks were observed at 215 nm and 217 nm for as-synthesized and calcined samples, respectively.

2017

The set of solid solutions ZrO 2 :0.005Eu 3+ /xF À (x = 0, 0.02, 0.04, 0.08, 0.10) was prepared via solid-state route. Synthesized powders were studied by means of XRD powder analysis, scanning electron microscopy and luminescence spectroscopy. The XRD patterns for all co-substituted samples are a composition of the monoclinic and cubic phases of zirconia. The products are crystallized in a compact form with an average size of particles about 50-150 nm. All studied samples at room temperature show in their PL spectra both wide band of the host-related emission (l max % 480 nm) and sharp peaks of the 5 D 0-7 F J (J = 0-4) radiation transitions in Eu 3+ ions under excitation with l ex = 393 nm. The total intensity of the Eu 3+ luminescence increases more than 6 times with fluorine content, x, increasing up to 0.08. Possible mechanisms of the luminescence behavior are discussed.

Journal of Physics D: Applied Physics, 2009

The structural, magnetic and luminescence properties of praseodymium-doped zirconia powders of compositions Pr 0.03 Zr 0.97 O 2 and Pr 0.05 Zr 0.95 O 2 synthesized by a sol-gel process have been investigated. X-ray diffraction patterns indicate that these materials crystallize in a tetragonal fluorite-type structure. Scanning electron microscopy shows that the powders exhibit an agglomerated microcrystalline structure and the grain size may be in the order of 5-20 µm. The study of the magnetic properties of these doped metal oxides indicates a Curie-Weiss behaviour in the temperature range (100-300) K that allow us to estimate an effective magnetic moment of 3.51 µ B , which indicates the presence of Pr 3+ in the grown samples. Cathodoluminescence spectra recorded at temperatures between 85 and 295 K show emission peaks that can be attributed to transitions between different states within the 4f 2 configuration of Pr 3+ ions incorporated in the zirconia crystal lattice. Thermoluminescence measured at temperatures ranging from 373 to 773 K and at 550 nm wavelength show an intense and broad peak around 653 K for the Pr-doped zirconia which is not observed in the undoped material.

Journal of the Optical Society of America B, 2004

The luminescence lifetime of the excited state 4 F 9/2 of Er 3ϩ-ions doped (0.05 mol. %) in ZrO 2 nanocrystals was found to be sensitive to the particle crystalline phase and size. Our analysis suggests that modifications of nonradiative relaxation mechanisms due to confinement effects are more important than the local symmetry structure of the host lattice in explaining the observed luminescence quenching.

Journal of Materials Science, 2014

Nanocrystalline ZrO 2 materials were prepared by sol-gel method combining different W = [H 2 O]/[ZTB] ratios (ZTB: zirconium tetrabutoxide) with 600, 800, and 1000°C annealing temperatures, yielding diverse phase compositions. A lower post-synthesis annealing temperature (600°C) favored the t-ZrO 2 tetragonal phase while higher temperatures (800 and 1000°C) yielded the monoclinic one (m-ZrO 2). Depending on the preparation conditions, mixed structure materials are readily obtained. The luminescence activator in the undoped ZrO 2 is assumed as trivalent titanium and emission bands are assigned to the 3d 1 (e g) ? 3d 1 (t 2g) transition. Due to weaker crystal field in m-ZrO 2 form, the Ti 3? emission band is red-shifted from 410 nm in t-ZrO 2 to 500 nm. The luminescence intensity of the t-ZrO 2 form is quenched at higher temperature than that of m-ZrO 2 , indicating higher activation energy and smaller Stokes shift. The undoped ZrO 2 excitation seems to involve photoionization of Ti 3? to Ti IV. Simultaneously, the freed electron is trapped to the oxygen vacancies (F ?? centers) created by Ti 3? /Ti IV charge compensation, so this can be considered as a metalto-host/ligand charge transfer. Since most of the excitation results in immediate emission, the traps are probably very shallow though deeper ones leads to the persistent luminescence from the undoped ZrO 2 .

Pure zirconia (ZrO 2 ) nano powders were prepared by hydrothermal method using three different precursors namely zirconium nitrate, zirconyl nitrate and zirconium oxy-chloride. The products were characterized by Powder X-Ray Diffraction (PXRD), Fourier Transform Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), UV-Visible spectroscopy. Photoluminescence behavior is studied with respect to different precursors while keeping other reaction parameters constant. The PXRD studies show the formation of monoclinic ZrO 2 nanopowders irrespective of precursor used. The average crystallite size calculated from X-ray line broadening ranges from 20 -30 nm. Upon excitation at 380 nm, the PL emission spectra of all the three compounds consists of intense bands centered at 416, 438, 467 nm along with less intense peaks at 518 and 624 nm. All these bands can be ascribed to the defects in the crystal (F + centers) and oxygen vacancy defects. The difference in the intensity of PL spectra with precursors is attributed to difference in the number of defect centers.

Central European Journal of Physics, 2014

A careful study of the phosphorescence afterglow and the thermoluminescence (TL) of sol-gel-prepared m-ZrO 2 nanocrystalline powders in an extended temperature range −100 to 300°C was carried out. Wavelength-resolved TL proved the existence of a single active luminescence centre in this temperature range. A TL method based on various heating rates was used to derive more reliable trap depths of 0.75, 0.95, 1.25, 1.46 and 1.66 eV whereas deconvolution methods provided somewhat lower values. The most intense room-temperature afterglows (that were easily observable beyond 1000 s) were obtained from samples annealed at 1250 and 1500°C, and were attributed mainly to depopulation of the 1.25 eV traps.

Journal of Non-Crystalline Solids, 2008

We obtained samarium-doped zirconia using two different routes. In one, atomic layer deposited thin crystalline films were doped by using ion implantation; this sample was mainly monoclinic. The other method, the skull-melting technique, yielded polycrystalline bulk zirconia containing both monoclinic and tetragonal phases of ZrO 2 . Thorough photoluminescence (PL) measurements of Sm emission in these materials were performed using pulsed laser excitation at 405, 320 and 230 nm, respectively corresponding to direct, defect-related and host-sensitized excitation. Both samples exhibited well-resolved emission series of Sm 3+ . In general, the recorded spectra may be considered as superpositions of two different sets of lines attributable to Sm 3+ centers in different crystalline phases of ZrO 2 . These results have been confirmed by time-resolved measurements, which also suggest that all emission lines originate from a common initial state ( 4 G 5/2 ) with a lifetime of about 1 ms. As expected, the host-mediated excitation leads to a prolonged decay profile attributed to the retarded energy transfer from host to guest.