Structural, magnetic and luminescent characteristics of Pr 3+ -doped ZrO 2 powders synthesized by a sol–gel method (original) (raw)
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Luminescence of Nanosized ZrO2 and ZrO2: Pr Powders
Solid State Phenomena, 2003
The time-resolved luminescence from different size ZrO 2 and ZrO 2 :Pr nanocrystals was studied. The pulsed electron beam (270 keV, 10 ns) was used for luminescence excitation. The luminescence band peaking at 2.8 eV is suggested to be of intrinsic origin. Luminescence intensity and decay kinetics depends on the nanocrystal size. The large size nanocrystals show more intense luminescence than small sized nanocrystals. This dependence arises due to nonradiative decay of electronic excitations at nanocrystal surface. The luminescence intensity from ZrO 2 :Pr nanocrystals is much lower than from undoped ZrO 2 nanocrystals. The surface area analysis was undertaken by BET (Braunaver, Emmet, Teller) method (Model Gemini 2360, Micromeritics Instruments Corp), using nitrogen as an adsorbate. The specific surface area (S) was determined for each powder. The average grain size (F) of nanocrystals was calculated
Luminescence of Nanosized ZrO2 and ZrO2: Pr Powders
Solid State Phenomena, 2003
The time-resolved luminescence from different size ZrO 2 and ZrO 2 :Pr nanocrystals was studied. The pulsed electron beam (270 keV, 10 ns) was used for luminescence excitation. The luminescence band peaking at 2.8 eV is suggested to be of intrinsic origin. Luminescence intensity and decay kinetics depends on the nanocrystal size. The large size nanocrystals show more intense luminescence than small sized nanocrystals. This dependence arises due to nonradiative decay of electronic excitations at nanocrystal surface. The luminescence intensity from ZrO 2 :Pr nanocrystals is much lower than from undoped ZrO 2 nanocrystals. The surface area analysis was undertaken by BET (Braunaver, Emmet, Teller) method (Model Gemini 2360, Micromeritics Instruments Corp), using nitrogen as an adsorbate. The specific surface area (S) was determined for each powder. The average grain size (F) of nanocrystals was calculated
Photoluminescent emission of Pr3+ ions in different zirconia crystalline forms
Optical Materials, 2008
Polycrystalline praseodymium doped-zirconia powders were synthesized by crystallization of a saturated solution and annealed in air at T a = 950°C. Monoclinic, tetragonal and cubic crystalline phases of zirconia were obtained. EDS studies showed homogeneous chemical composition over all the powders particles and chemical elemental contents in good agreement with the incorporation of Pr 3+ ion in Zr 4+ sites. XRD patterns showed stabilization of tetragonal and cubic phases at 1.28 and 2.87 at.% of Pr 3+ doping concentrations, respectively. Both unit cells expand when Pr 3+ content increases. All samples showed a crystallite size lower than 27 nm. Diffuse reflectance studies exhibited the presence of the 4f5d absorption band of Pr 3+ , and absorption peaks in 440-610 nm region associated with 4f inter-level electronic transitions in Pr 3+ ion. Low temperature (20 K) photo-luminescent spectroscopic measurements over excitation of 488 nm for praseodymium doped zirconia, showed multiple emission peaks in the 520-900 nm range of the electromagnetic spectrum, associated with typical 4f inter-level electronic transition in Pr 3+. Incorporation of Pr 3+ in more than one zirconia crystalline phase and the incorporation in cubic C 2 sites, were observed. Zirconia powders presented significant differences in its emission spectra as a function of the type of crystalline phase compounds.
Luminescence properties of Sm3+-doped polycrystalline ZrO2
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.
Scripta Materialia, 2009
In this paper we report observation of highly efficient Pr 3+ 4f-4f emission in ZrO 2 (0.5 mol.% Pr 3+ ) fine nanocrystals stabilized by Y 2 O 3 (7 mol.%). The nanocrystals were obtained via a hydrothermal microwave-driven process followed by heat treatment at 1200°C. The samples excited by 266 or 297 nm light exhibit a remarkable sensitizing of Pr 3+ photoluminescence. The chromaticity analysis indicates the usability of the studied material as a red luminescent phosphor.
Optical Materials, 2002
Pure and rare earth doped zirconium oxide was prepared by the sol–gel process and annealed at 1000 °C to stabilize the monoclinic phase. Thermoluminescence (TL) and photoluminescence (PL) under Gamma and UV irradiation were performed. A single TL peak was present at 135 °C under gamma irradiation, whereas under UV irradiation the TL presented two peaks at 62 and 130 °C. The PL of pure and rare earth doped samples was also characterized. The experimental spectra suggest the presence of energy transfer processes between the dopant (Sm3+) and the host (ZrO2).
Structure–property relationship of luminescent zirconia nanomaterials obtained by sol–gel method
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 .
Optical Materials, Volume 31, Issue 8, Pages 1134–1143, 2009
(Sr0.995Tm0.005)ZrO3 (STZO) powders were prepared by the polymeric precursor method and heat treated at different temperatures for 2 h under oxygen flow. These powders were analyzed by X-ray diffraction (XRD), Ultraviolet–visible (UV–vis) absorption spectroscopy, photoluminescence (PL) measurements, field-emission gun-scanning electron microscopy (FEG-SEM) and energy dispersive X-ray spectrometry (EDXS). XRD patterns revealed that the powders crystallize in an orthorhombic structure without the presence of secondary phases. UV–vis absorption spectra suggest that the STZO powders heat treated at low temperatures present intermediary energy levels within the band gap as consequence of structural defects in the lattice. PL measurements indicated the presence of broad, broad/narrow and narrow bands in STZO powders. The broad bands were associated to the asymmetric STZO structure and/or p–d transitions while, the narrow bands were ascribed to f–f transitions arising from thulium ions. A simple model was proposed in order to explain the PL behavior of these powders. FEG-SEM micrographs showed that these powders are composed by several microparticles with irregular morphologies and agglomerated nature. EDXS data were used for analyses of chemical compositional of powders.
Chemical synthesis of nanocrystalline tin-doped cubic ZrO2 powders
Materials Letters, 2003
The nanocrystalline powders of the system SnO 2-ZrO 2 has been prepared using zirconium oxalate and tin tartarate, which are also synthesised from their organic and inorganic precursors. The aqueous solutions of oxalate and tartarate are mixed with proper proportions and with polyvinyl alcohol to form the polymer precursor solution. This is evaporated, pyrolysed and calcined to nanocrystalline powders. The phase of the powders is cubic at the temperature of calcination of 700 jC with the crystallite size ranges from 15 to 25 nm, whereas the particles size ranges from 30 to 50 nm for the sample containing 5 mol% SnO 2. The shapes of the particles are oval and spherical. The alloying can be done up to 20 mol% with SnO 2. The material is promising for chemical sensors.