Real structure of undoped Y<sub>2</sub>O<sub>3</sub> single crystals

Hanic, F.; Hartmanová, M.; Knab, G. G.; Urusovskaya, A. A.; Bagdasarov, Kh. S.

doi:10.1107/s0108768184001774

Cited by 168 publications

(67 citation statements)

References 2 publications

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“…The symmetry of coordination polyhedra are responsible for the splitting of yttrium 3d orbitals [27], but also of 4f orbitals in REE, which can be substituted for yttrium in the crystal structure of Y 2 O 3 polymorphs. For c-Y 2 O 3 two six-fold coordinated cation positions with C 3i and C 2 symmetry exist [11]. When occupied with REE, 4f orbitals splits and luminescent emission takes place after laser excitation [28].…”

Section: Discussionmentioning

confidence: 99%

“…A very good substitution of dopants is insured by similar crystal-chemical constraints for rare earth ions and yttrium [9,10]. Y 2 O 3 structure corresponds to the C-type cubic bixbyite structure, space group Ia3 [11,12] with 16 formula units in the elementary cell. There are 32 cation (six-fold coordinated) sites available for substitution of lanthanide ions: eight are centrosymmetric with C3i symmetry and 24 noncentrosymmetric with C 2 symmetry (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Influence of mechanochemical processing to luminescence properties in Y2O3 powder

Gajović

Tomašić

Djerdj

et al. 2008

Journal of Alloys and Compounds

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In high purity Y 2 O 3 powders presence of small amount of erbium ions in cation sites was identified due to the luminescence bands observed by Raman spectrometer. The decrease of the luminescence intensity during high-energy ball-milling was explained. The mechanochemical processing induced the changes of Y 2 O 3 microstructure introducing distortion of the crystal lattice and oxygen vacancies in the cubic phase, substitution of tungsten at the cation sites in c-Y 2 O 3 , and incomplete phase transition of Y 2 O 3 from the cubic to the monoclinic structure. The influence of the particle-size decrease, caused by ball-milling, to luminescence was also considered.Keywords: Oxide materials; Mechanochemical processing; Microstructure; Luminescence IntroductionYttrium sesquioxide (Y 2 O 3 ) ceramics have been intensively investigated for different technological purposes. For decades yttrium oxide has been an important material in ceramic industry, from constituent of ceramic superconductors [1,2], to wellknown YSZ ceramics [3,4]. Y 2 O 3 is also used in electronic applications as a part of metal-oxide-semiconductor heterostructures in MOS transistors [5][6][7][8]. It also plays an important role in preparation of novel light-emitting materials. Y 2 O3 is used as a refractory matrix in rare earth ion doped laser materials [9]. It is selected as a host because of favorable thermomechanical properties (high melting point, phase stability, low thermal expansion). A very good substitution of dopants is insured by similar crystal-chemical constraints for rare earth ions and yttrium [9,10]. Y 2 O 3 structure corresponds to the C-type cubic bixbyite structure, space group Ia3 [11,12] with 16 formula units in the elementary cell. There are 32 cation (six-fold coordinated) sites available for substitution of lanthanide ions: eight are centrosymmetric with C3i symmetry and 24 noncentrosymmetric with C 2 symmetry (Fig. 1a). The sites with C 3i symmetry have a smaller crystal field, so Stark splitting of 4f orbital is smaller [13]. Moreover, since C 3i site has an inversion center, the selection rules forbid the electron-dipole (ED) transitions, but thermal fluctuations of Y 2 O 3 lattice destroy the perfect C 3i symmetry locally [14], and the ED transitions can occur. There is no center of inversion in the C 2 site and the luminescence of incorporated lanthanide ions is predominantly connected with this site. At the pressure of 10-13 GPa cubic Y 2 O 3 exhibits the first-order reconstructive (irreversible) phase transition [15] to monoclinic structure, space group C2/m [16]. Monoclinic structure has 6 Y 2 O 3 formula units in the elementary cell with 3 nonequivalent cation sites (seven-fold coordinated) and Cs symmetry (Fig. 1b). Bihari et. al [17] observed three sets of luminescence lines in doped monoclinic Y 2 O 3 , which correspond to three nonequivalent cation sites. In this work the luminescence bands was observed in high purity Y 2 O 3 (99.99%). The origin of the luminescence bands was identified and their propert...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of mechanochemical processing to luminescence properties in Y2O3 powder

Gajović

Tomašić

Djerdj

et al. 2008

Journal of Alloys and Compounds

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“…1a). XRL spectrum of the undoped ceramics at 85 K is fitted into the elementary Gaussian shape bands with the maxima near 3.40, 3.06, 2.67, 2.33, 2.09, and 1.91 eV considering the features of Y 2 O 3 crystal structure [1] and the possibility of the formation of the short-lived and stable hole and electron centers of V -and F -type [2][3][4] by the ionizing radiation in the oxide compounds [11][12][13]. The doping of the material by europium ions leads to the appearance of Eu 3+ centers luminescence with C 2 symmetry.…”

Section: Resultsmentioning

confidence: 99%

“…h [1]. Such structure derives from the structure of fluorite (CaF 2 ) and some anions are not in this structure.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Europium Impurity on the Recombination Luminescence in Y₂O₃

Novosad

Bordun

et al. 2018

Acta Phys. Pol. A

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In this work the researched results of the spectral characteristics of the luminescence and the thermostimulated luminescence curves of Y2O3 and Y2O3:Eu ceramic materials at the X-ray excitation in the 85-295 K range were generalized. Considering the features of Y2O3 crystal structure and the possibility of the formation of the shortlived and stable hole and electron centers of V -and F -type by the ionizing radiation X-ray luminescence spectrum of ceramics at 85 K is fitted into the elementary Gaussian shape bands with the maxima near 3.40, 3.06, 2.67, 2.33, 2.09, and 1.91 eV. The main 3.40 and 3.06 eV bands of the luminescence are caused by the self-trapped excitons of (YO6) 9− complex, when the cation is localized in the field of the trigonal (C3i) and monoclinic (C2) symmetries. The emission at 2.67 eV and the weak bands in the 1.65-2.61 eV region are considered as the radiation of excitons localized on the anion vacancies and the electron centers of F -type (F + , F and F − ). The thermoluminescence of Y2O3 in the 186 and 204 K main peaks range is connected with the thermal destruction of the self-trapped states of O − ions that located in the field of the trigonal and monoclinic symmetries. The activator bands caused by 5 D0 → 7 Fj electronic transitions in Eu 3+ are only observed in the X-ray and thermostimulated luminescence spectra of Y2O3:Eu ceramics. It was assumed that both at the X-rays irradiation and an optical excitation in the band of the charge transfer of Y2O3:Eu sample the energy goes to Eu 3+ through (Eu 2+ O − ) complexes (states) of the charge transfer.

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“…It can be seen that the resistivity of both films increases exponentially with decreasing temperature in the measurement range from 300 to 95 K, which indicates that both films have semiconductor behavior. In comparison with the YSCO single-phase films grown at 800 °C, the resistivity of the nanocomposite films grown at 900 °C decreases roughly by a factor of four over the entire temperature range of 95−300 K. To understand the electrical transport behavior in both films, the temperature dependent resistivity ρ(T) is fitted by Mott's variable range hopping (VRH) model [4]. In the case of ρ(T)=ρ 0 * exp(T 0 /T) -1/4 (where ρ 0 is the pre-exponential factor and T 0 is a characteristic temperature), a linear dependence of lnρ versus T -1/4 is obtained for both films, as shown in the inset in Figure 2, which indicates that hopping conduction is dominant in the measured temperature range for both films.…”

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confidence: 99%

Microstructure and Electrical Conductivity of (Y, Sr)CoO_3-δ Thin Films Tuned by the Film-Growth Temperature

Jing

et al. 2017

Microsc Microanal

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Perovskite-based rare earth cobaltates have been the topic of extensive research since they possess fascinating electrical and magnetic properties [1,2]. Y x Sr 1−x CoO 3−δ (YSCO) compounds with roomtemperature ferromagnetic properties were reported. In particular, the YSCO compound with x≈0.25 exhibits the highest Curie temperature (T c ≈335 K) among the perovskite-based cobaltates and the properties of YSCO could be modulated by its chemical composition [3]. In contrast to the considerable studies on the YSCO bulk materials, investigations on the microstructure and the properties of the YSCO thin films are limited. In this work, we report a detailed study on the microstructural and electrical properties of the Y x Sr 1−x CoO 3−δ (x=0.25) films, which were prepared at different growth temperatures on the (La 0.289 Sr 0.712 )(Al 0.633 Ta 0.356 )O 3 (LSAT) substrates.The YSCO thin films are grown on single crystalline LSAT (001) substrates at 800 °C and 900 °C, respectively, using a magnetron sputtering system. The flowing pressure is 1 mbar with the mixed ambient of Ar and O 2 at the ratio of 1:1. After the film growth, the films are annealed for 15 minutes in a mixture gas of Ar and O 2 (400 mbar) in a ratio of 1:1, and then cooled down to room temperature in 30 minutes. Cross-sectional specimens were prepared by focused ion beam (FIB) technique (FEI Dualbeam Helios NanoLab 600i). Transmission electron microscopy (TEM) observation and selected area electron diffraction (SAED) are carried out on a JEOL 2100 microscope, operated at 200 kV. Energy-dispersive X-ray spectroscopy (EDS) data and high-angle annular dark-field (HAADF) images are obtained in a JEOL ARM 200F. The electrical properties of the films are measured using a Physics Property Measurement System (PPMS, Quantum Design). (001) substrates at 800 °C and 900 °C, respectively, viewed along the [100] zone axis of the substrates. From the image of the cross-sectional samples the thickness of the films is measured as about 100 nm. The films prepared at 800 °C show a homogeneous contrast and a sharp interface to the substrate, indicating a perfect epitaxy of the films. In contrast, In Figure 1 (b) nano-scale columnar contrast is evident in the YSCO films prepared at 900 °C, which comes from second phase. The EDS spectrum of the second-phase particles is inserted in (b), which indicates that the secondary phase is Y 2 O 3 . Importantly, it can be seen that Y 2 O 3 columns either start at the film-substrate interface or form within the film in a self-assembled manner. The size of the Y 2 O 3 columns is typically in a range of 4−10 nm in the in-plane direction and 60−80 nm in the out-of-plane direction. Electronic address:

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Real structure of undoped Y₂O₃ single crystals

Cited by 168 publications

References 2 publications

Influence of mechanochemical processing to luminescence properties in Y2O3 powder

Influence of mechanochemical processing to luminescence properties in Y2O3 powder

The Influence of Europium Impurity on the Recombination Luminescence in Y₂O₃

Microstructure and Electrical Conductivity of (Y, Sr)CoO_3-δ Thin Films Tuned by the Film-Growth Temperature

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Real structure of undoped Y2O3 single crystals

Cited by 168 publications

References 2 publications

Influence of mechanochemical processing to luminescence properties in Y2O3 powder

Influence of mechanochemical processing to luminescence properties in Y2O3 powder

The Influence of Europium Impurity on the Recombination Luminescence in Y2O3

Microstructure and Electrical Conductivity of (Y, Sr)CoO3-δ Thin Films Tuned by the Film-Growth Temperature

Contact Info

Product

Resources

About

Real structure of undoped Y₂O₃ single crystals

The Influence of Europium Impurity on the Recombination Luminescence in Y₂O₃

Microstructure and Electrical Conductivity of (Y, Sr)CoO_3-δ Thin Films Tuned by the Film-Growth Temperature