scholarly journals Effect of Ca 2+ and Zr 4+ co-doping on the optical properties of Gd 3Al 2Ga 3O 12: Ce single crystals

2019 ◽  
Vol 5 (3) ◽  
pp. 101-105
Author(s):  
Valentina M. Kasimova ◽  
Nina S. Kozlova ◽  
Oleg A. Buzanov ◽  
Evgeniya V. Zabelina
Keyword(s):  
Single Crystals ◽  
Light Yield ◽  
Optical Transmittance ◽  
High Energy ◽  
Refractive Indices ◽  
Optical Parameters ◽  
Visible Radiation ◽  
Co Doping ◽  
Positron Emission ◽  
Co Doped

Scintillation materials capable of transforming absorbed high-energy particles into visible radiation photons find multiple applications including advanced medical visualization methods. Gd3Al2Ga3O12 : Ce is a promising oxygen-containing sсintillator for fabrication of detecting crystals of positron emission tomographs due to its unique properties, e.g. high density, high light yield, radiation hardness etc. However its kinetic parameters currently restrict its use in this field. Attempts at improving the luminescence rise and decay time kinetics by introducing additional impurities have become a top priority task for many researchers. Analyzing literary data one can conclude that the optical parameters of co-doped crystals have been studied insufficiently or have not been studied at all. We have studied Ca2+ and Zr4+ co-doped Gd3Al2Ga3O12 : Ce single crystals by optical spectroscopy in the 200–2200 nm. We have taken the optical transmittance, absorption and reflection spectra and measured the refractive indices. Dispersion curves have been obtained by approximation of experimental refractive indices using the Brewster method and the Cauchy equation. Material constants of these equations have been estimated for each of the co-doped crystals.

scholarly journals Superconductivity in Cu Co-Doped SrxBi2Se3 Single Crystals

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3899 ◽  
Author(s):  
Aleksandr Yu. Kuntsevich ◽  
Victor P. Martovitskii ◽  
George V. Rybalchenko ◽  
Yuri G. Selivanov ◽  
Mikhail I. Bannikov ◽  
...  
Keyword(s):  
Critical Temperature ◽  
Transport Properties ◽  
Single Crystals ◽  
Electron Density ◽  
Doping Level ◽  
Carrier Density ◽  
Host Matrix ◽  
Topological Superconductor ◽  
Co Doping ◽  
Co Doped

In this study, we grew Cu co-doped single crystals of a topological superconductor candidate Sr x Bi 2 Se 3 , and studied their structural and transport properties. We reveal that the addition of even as small an amount of Cu co-dopant as 0.6 atomic %, completely suppresses superconductivity in Sr x Bi 2 Se 3 . Critical temperature (∼2.7 K) is rather robust with respect to co-doping. We show that Cu systematically increases the electron density and lattice parameters a and c. Our results demonstrate that superconductivity in Sr x Bi 2 Se 3 -based materials is induced by significantly lower Sr doping level x < 0.02 than commonly accepted x ∼ 0.06 , and it strongly depends on the specific arrangement of Sr atoms in the host matrix. The critical temperature in superconductive Sr-doped Bi 2 Se 3 is shown to be insensitive to carrier density.

Effect of Co-Doping on Electronic and Magnetic Properties in Ti2NiAl Heusler Alloy

2012 ◽  
Vol 602-604 ◽  
pp. 575-578
Author(s):  
Bo Wu ◽  
Xiu De Yang ◽  
Song Zhang
Keyword(s):  
Heusler Alloy ◽  
Density Functional ◽  
Magnetic Moments ◽  
High Energy ◽  
Type Structure ◽  
Local Spin Density Approximation ◽  
Lattice Constants ◽  
Co Doping ◽  
The Density Functional Theory ◽  
Co Doped

By using local spin density approximation (LSDA) scheme within the density functional theory (DFT), the structure, magnetism and electronic properties of Co-doped Heusler alloy Ti2NiAl with Hg2CuTi- and Cu2MnAl-type structure are comprehensively investigated. The results revealed that whole of the doped alloys with Hg2CuTi-type structure are ground configurations and half-metallic. With the increase of Co-doped concentration, the lattice constants and total magnetic moments in per unit are changed linearly, and the discrepancies of total energy between Hg2CuTi- and Cu2MnAl structure are also enhanced. Analysis on density of states (DOS) revealed that the Fermi level should gradually move to high-energy orientation with increasing Co content due to stronger hybridization of d-electronic atoms.

scholarly journals Enhanced Electrochemical Performance of LiNi0.5Mn1.5O4 Composite Cathodes for Lithium-Ion Batteries by Selective Doping of K+/Cl− and K+/F−

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2323
Author(s):  
Aijia Wei ◽  
Jinping Mu ◽  
Rui He ◽  
Xue Bai ◽  
Xiaohui Li ◽  
...  
Keyword(s):  
Rate Capability ◽  
Lithium Ion ◽  
High Energy ◽  
Electrochemical Kinetics ◽  
Doping Amount ◽  
Solid State Method ◽  
Teller Distortion ◽  
Co Doping ◽  
Composite Cathodes ◽  
Co Doped

K+/Cl− and K+/F− co-doped LiNi0.5Mn1.5O4 (LNMO) materials were successfully synthesized via a solid-state method. Structural characterization revealed that both K+/Cl− and K+/F− co-doping reduced the LixNi1−xO impurities and enlarged the lattice parameters compared to those of pure LNMO. Besides this, the K+/F− co-doping decreased the Mn3+ ion content, which could inhibit the Jahn–Teller distortion and was beneficial to the cycling performance. Furthermore, both the K+/Cl− and the K+/F− co-doping reduced the particle size and made the particles more uniform. The K+/Cl− co-doped particles possessed a similar octahedral structure to that of pure LNMO. In contrast, as the K+/F− co-doping amount increased, the crystal structure became a truncated octahedral shape. The Li+ diffusion coefficient calculated from the CV tests showed that both K+/Cl− and K+/F− co-doping facilitated Li+ diffusion in the LNMO. The impedance tests showed that the charge transfer resistances were reduced by the co-doping. These results indicated that both the K+/Cl− and the K+/F− co-doping stabilized the crystal structures, facilitated Li+ diffusion, modified the particle morphologies, and increased the electrochemical kinetics. Benefiting from the unique advantages of the co-doping, the K+/Cl− and K+/F− co-doped samples exhibited improved rate and cycling performances. The K+/Cl− co-doped Li0.97K0.03Ni0.5Mn1.5O3.97Cl0.03 (LNMO-KCl0.03) exhibited the best rate capability with discharge capacities of 116.1, 109.3, and 93.9 mAh g−1 at high C-rates of 5C, 7C, and 10C, respectively. Moreover, the K+/F− co-doped Li0.98K0.02Ni0.5Mn1.5O3.98F0.02 (LNMO-KF0.02) delivered excellent cycling stability, maintaining 85.8% of its initial discharge capacity after circulation for 500 cycles at 5C. Therefore, the K+/Cl− or K+/F− co-doping strategy proposed herein will play a significant role in the further construction of other high-voltage cathodes for high-energy LIBs.

Photoluminescence, ellipsometric, optical and morphological studies of sprayed Co-doped ZnO films

2016 ◽  
Vol 30 (15) ◽  
pp. 1650171 ◽  
Author(s):  
O. Gençyılmaz ◽  
F. Atay ◽  
İ. Akyüz
Keyword(s):  
Refractive Index ◽  
Surface Properties ◽  
Extinction Coefficient ◽  
Zno Films ◽  
Optical Parameters ◽  
Pl Spectra ◽  
Co Doping ◽  
Morphological Studies ◽  
Doped Zno ◽  
Co Doped

In this study, undoped and cobalt (Co)-doped zinc oxide (ZnO) films were successfully produced by ultrasonic spray pyrolysis (USP) technique at low temperature (350[Formula: see text]C). The optical and surface properties were investigated as a function of Co content. The optical parameters (thickness, refractive index and extinction coefficient) were determined using spectroscopic ellipsometry (SE) and it was seen that the refractive index and extinction coefficient values of Co-doped ZnO films decreased slightly depending on the increasing of Co doping. For investigation, the transmittance and photoluminescence (PL) spectra of the films, UV–Vis spectrophotometer and PL spectroscopy were used at room temperature. The transmittance spectra show that transmittance values decreased and Co[Formula: see text] ions substitute Zn[Formula: see text] ions of ZnO lattice. The optical band gap values decreased from 3.26 eV to 2.85 eV with the changing of Co content. The results of PL spectra exhibit the position of the different emission peaks unchanged but the intensity of peaks increased with increasing Co doping. Also, the surface properties of the films were obtained by atomic force microscopy (AFM) and these results indicated that the surface morphology and roughness values were prominently changed with Co doping.

Crystal Growth and Scintillation Properties of Ce3+ and Mg2+ Co-Doped LiCaAlF6 Single Crystal

2012 ◽  
Vol 508 ◽  
pp. 240-246 ◽  
Author(s):  
Akihiro Yamaji ◽  
Yutaka Fujimoto ◽  
Takayuki Yanagida ◽  
N. Kawaguchi ◽  
Yoshisuke Futami ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Single Crystal ◽  
Single Crystals ◽  
Light Yield ◽  
Emission Peak ◽  
Absorption Coefficients ◽  
Nominal Concentration ◽  
Lithium Glass ◽  
Decay Times ◽  
Co Doped

Ce and Mg Co-Doped LiCaAlF6 (LiCAF) Single Crystals Were Grown by Micro-Pulling-down (μ-PD) Method and the Optical and Scintillation Properties of Obtained Crystals Were Measured. The Grown Crystals Were Crack-Free and Had 30-50 mm in Length and 2 Mm in Diameter. Absorption Coefficients Were Proportional to the Ce Nominal Concentrations. the Radioluminescence Spectra under 5.5 Mev Alpha-Ray Irradiation Showed Emission Peak at 290 and 310 nm due to Ce3+ 5d-4f Transitions, and Were Agreement with those of Ce Single-Doped LiCaF. The Highest Light Yield under 5.5 Mev Alpha-Ray Irradiation of Ce 4% and Mg 2% Co-Doped LiCaF Was Found to Be 0.6 Times than that of Lithium Glass Scintillator GS-20. Comparing the Light Yield of Licaf Samples with the Fixed Ce Nominal Concentration and Different Mg Co-Doped Concentrations, the Light Yield Increased with an Increase of Mg Nominal Concentration. the Alpha-Ray Excited Decay Times Were Constantly 45-50 ns.

scholarly journals Influence of Ca2+ and Zr4+ codoping on the optical characteristics of Gd3Al2Ga3O12:Ce single-crystal

2019 ◽  
Vol 22 (1) ◽  
pp. 27-34
Author(s):  
V. M. Kasimova ◽  
N. S. Kozlova ◽  
O. A. Buzanov ◽  
A. P. Kozlova ◽  
E. V. Zabelina
Keyword(s):  
Single Crystal ◽  
Light Output ◽  
High Energy ◽  
Optical Characteristics ◽  
Visible Radiation ◽  
Positron Emission ◽  
Priority Task ◽  
High Energy Particles ◽  
Literature Data Analysis ◽  
Crystal Element

Scintillation materials that can convert absorbed high-energy particles into photons of visible radiation find many applications, in particular in modern methods of medical imaging. Gd3Al2Ga3O12 : Ce is promising single crystal for use as a detecting crystal element of the positron emission tomographs due to its unique properties: high density, high light output, radiation hardness, etc. However, its scintillation kinetics currently limit the use of this crystal. Changing of these kinetics by codoping becomes a priority task, which is considered in many papers. The literature data analysis showed that the optical characteristics of such codoped crystals were not well enough studied or were not investigated at all. In this regard, the spectral dependences of transmission, absorption and reflection are measured using optical spectroscopy for Gd3Al2Ga3O12:Ce, Gd3Al2Ga3O12 : Ce,Ca and Gd3Al2Ga3O12 : Ce,Zr. Dispersion dependences of refractive in dices are obtained by approximating the refractive indices measured using the Brewster method. The approximation was carried out using the Cauchy equation. The material constants of this equation are estimated.

scholarly journals Optical characteristics of single crystal Gd3Al2Ga3O12 : Ce

2018 ◽  
Vol 4 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Nina S. Kozlova ◽  
Oleg A. Buzanov ◽  
Valentina M. Kasimova ◽  
Anna P. Kozlova ◽  
Evgeniya V. Zabelina
Keyword(s):  
Radiation Detection ◽  
Light Yield ◽  
High Energy ◽  
Optical Quality ◽  
Optical Characteristics ◽  
Refractive Indices ◽  
Rare Earth Ion ◽  
High Optical Quality ◽  
Detection Techniques ◽  
Spectrophotometric Methods

New emerging high-energy radiation detection techniques are based on the use of rare-earth ion doped materials. There is a great demand for new inorganic scintillators for medical applications, including X-ray and g radiation detection. In these applications, the new scintillating materials must comply with the main requirements such as high optical quality, high light yield, short response time etc. Materials satisfying these requirements include Gd3Al2Ga3O12: Ce (GAGG : Ce) scintillating single crystals. By now the optical characteristics of GAGG : Ce have been studied insufficiently. We have therefore measured the spectral reflectance and transmittance characteristics of these crystals using optical spectroscopy in the 200–750 nm range. We have also measured the absorbance and refractive indices and the extinction coefficients, and assessed the optical band gap for GAGG : Ce crystals. For measuring the refractive indices, we have used two spectrophotometric methods, i.e. by the measured Brewster angle and by the reflectance for low incidence angles, i.e., close to the normal. Based on the results we have drawn up the dispersion functions of the refractive indices.

Cooperative Energy Transfer Up-/Down-Conversion Luminescence in Tb3+/Yb3+ Co-Doped Cubic Na5Lu9F32 Single Crystals by Gd3+ Co-Doping

2017 ◽  
Vol 17 (6) ◽  
pp. 3163-3169 ◽  
Author(s):  
Shinan He ◽  
Haiping Xia ◽  
Qingyang Tang ◽  
Qiguo Sheng ◽  
Jianli Zhang ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Single Crystals ◽  
Co Doping ◽  
Down Conversion ◽  
Co Doped ◽  
Cooperative Energy

scholarly journals Effect of co-doping on dielectric function spectra and static refractive indices of single-walled carbon nanotubes: A first principles study

2017 ◽  
Vol 95 (12) ◽  
pp. 1194-1199 ◽  
Author(s):  
Deepa Sharma ◽  
Neena Jaggi
Keyword(s):  
Carbon Nanotubes ◽  
Refractive Index ◽  
Dielectric Function ◽  
Single Walled Carbon Nanotubes ◽  
Refractive Indices ◽  
Single Walled Carbon ◽  
Co Doping ◽  
Static Refractive Index ◽  
Walled Carbon Nanotubes ◽  
Co Doped

This paper details a density functional theory (DFT) based ab initio study on the effect of co-doping on the dielectric function spectra and refractive indices of single-walled carbon nanotubes (SWCNTs). Dielectric function spectra of a pristine (8,0) SWCNT; (8,0) SWCNT co-doped with aluminum (Al) and phosphorus (P); (8,0) SWCNT co-doped with Al, P, and nitrogen (N); (9,0) SWCNT doped with Al; and (9,0) SWCNT co-doped with Al and boron (B) have been calculated using DFT-based Cambridge sequential total energy package (CASTEP) code. Polarized and unpolarized light as well as light through polycrystalline media have been considered. Analysis involves calculation and comparison of static refractive indices of the pristine and co-doped SWCNTs. Co-doping with Al and P results in a substantial increase in the value of the static refractive index while co-doping of Al, N, and P results in a reduction in the value of static refractive index though it does not fall lower than that of the pristine SWCNT. Thus, it can be concluded that co-doping with atoms of different combinations of elements can be evolved as a novel and effective tool for tuning the dielectric function and static refractive index values of SWCNTs. It will prove to be highly significant for effective designing of various sensitive optical devices using SWCNTs.

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