Optical Investigation of Sm doped ZrO2

Journal of Applied Physics, 2012

ZrO 2 samples with 11% Nd and La doping and with 7, 9, 11, and 13% Gd doping have been prepared by co-precipitation route followed by sintering at 700 C and 1100 C, for potential application as high conductivity electrolytes in solid oxide fuel cells. The samples have been characterized by x-ray diffraction with laboratory x-ray source of Cu K a radiation and extended x-ray absorption fine structure (EXAFS) spectroscopy measurement at Zr K edge with synchrotron radiation. The XRD spectra have been analyzed to determine the structure of the samples and the EXAFS data have been analyzed to find out relevant local structure parameters of the Zr-O and Zr-Zr shells, viz., bond distances, co-ordinations, and disorder parameters. The effect of change in ionic radius as well as concentration of the dopants on the above parameters has been thoroughly studied. The experimental results, in some cases, have also been corroborated by first principle calculations of the energetics of the systems. V C 2012 American Institute of Physics.

2001

Photoluminescence (PL) of pure and 0.2 mol percent Sm3+ doped zirconium oxide prepared by the Sol-Gel process and annealed at 1000 degrees C to stabilize the monoclinic phase were performed. The experimental spectra suggest the presence of energy transfer pro9cesses between the host and the dopant when the host was excited with a signal centered at 320 nm. The Sm3+ doped monoclinic zirconium oxide shows strong emission at the green and red bands, corresponding to the 4G5/2 yields 6H5/2 and 4G5/2 yields 6H7/2 samarium transition, respectively; whereas the undoped sample only shows a broad band emission centered at 495 nm. The main mechanism that allows the samarium emission under UV-excitation appears to be non-radiative energy transfer from the ZoO2 host to the Sm3+ ions.

The Journal of Physical Chemistry C, 2012

The local structure of europium doped and impregnated ZrO 2 in the amorphous state and during crystallization is investigated by in situ X-ray diffraction and in situ Raman, high-resolution transmission electron microscopy (HRTEM) and time-resolved photoluminescence spectroscopy. From Raman spectra excited at three different wavelengths (λ ex = 488, 514, and 633 nm), both phonon modes of ZrO 2 and photoluminescence (PL) corresponding to europium electronic transitions were investigated. In the assynthetized state, samples were X-ray and Raman amorphous with few tetragonal (also monoclinic) crystallites being observed under HRTEM microscopy. In situ XRD patterns show that all samples crystallize in the tetragonal phase around 450°C. The time-resolved PL spectra of europium doped and impregnated ZrO 2 show spectral dynamics with time delay after lamp/laser pulse which is assigned to the coexistence of the different amorphous and crystalline components or unreacted europium precursor. From in situ Raman spectra, crystallization was detected at 300−350°C, monitoring for the characteristic tetragonal-like 5 D 0 − 7 F 2 emission of europium at 606 nm. The ratio of tetragonal to amorphous emission increased abruptly from ca. 2−4% at 300−400°C to almost 25% at 400−450°C, whereas at 500°C the emission is mostly tetragonal. A similar trend was found with the ex situ calcined samples, but relative strong tetragonal emission was observed at lower temperature in the range of 350 to 400°C.

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.

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.

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.

Optical Materials, 2005

Strong visible emission under UV (320 nm) and IR (967 nm) excitation on ZrO 2 :Sm 3+ and ZrO 2 :Er 3+ nanophosphors were obtained and the concentration effect on the luminescence and crystalline structure is reported. Experimental results shows that phase composition depend on the ion concentration. The visible emission obtained under UV excitation is produced by the transitions 4 G 5/2 ! 6 H 5/2,7/2,9/2 of Sm 3+ through a non-radiative energy transfer process from the host to the active ion. Energy transfer and quenching effect due to ion concentration was confirmed by measuring the fluorescence decay time. Green (545 nm) and red (680 nm) emissions bands were observed under IR excitation troughs an upconversion process. It was proved that visible emission for both nanophosphor could be tuned by controlling the ion concentration. The nature of this behavior is discussed taking into account the phase composition for ZrO 2 :Sm 3+ and two photon absorption and cross-relaxation process was considered for ZrO 2 :Er 3+ nanophosphor.

PHYSICAL REVIEW B 85(15), 155202 (2012)

deA combination of experiments and ab initio quantum-mechanical calculations has been applied to examine electronic, structural, and hyperfine interactions in pure and Ta-doped zirconium dioxide in its monoclinic phase (m-ZrO2). From the theoretical point of view, the full-potential linear augmented plane wave plus local orbital (APW + lo) method was applied to treat the electronic structure of the doped system including the atomic relaxations introduced by the impurities in the host in a fully self-consistent way using a supercell approach. Different charge states of the Ta impurity were considered in the study and its effects on the electronic, structural, and hyperfine properties are discussed. Our results suggest that two different charge states coexist in Ta-doped m-ZrO2. Further, ab initio calculations predict that depending on the impurity charge state, a sizeable magnetic moment can be induced at the Ta-probe site. This prediction is confirmed by a new analysis of experimental data.

Proceedings of …, 2001

Photoluminescence (PL) of pure and 0.2 mol% Sm3 doped zirconium oxide prepared by the Sot-Gel process and annealed at 1 000°C to stabilize the monoclinic phase were performed. The experimental spectra suggest the presence of energy transfer processes between the host (Zr02) and the dopant (Sm3+), when the host was excited with a. 3+. .. .. . signal centered at 320 nm. The Sm doped monochnic zirconium oxide shows strong emission at the green (569 nm) and red (607, 613 and 61 8 nm) bands, corresponding to the 4G512-6H512 and 4G512-> 6H712 samarium transition, respectively; whereas the undoped sample only shows a broad band emission centered at 495 nm. The main mechanism that allows the samarium emission under UV-excitation appears to be non-radiative energy transfer from the Zr02 host to the Sm3 ions.