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1.
《Ceramics International》2021,47(18):25708-25720
Tb3+/Dy3+ co-doped CaLa2(WO4)4 (CLW: Tb3+/Dy3+) and its derivatives were synthesized by the sol-gel method. The morphology, thermal, structure and luminescent-optical properties the as-prepared light-emitting phosphors were characterized by utilizing scanning electron microscopy (SEM), differential thermal analysis (DTA)-thermogravimetric analysis (TG), X-ray diffraction (XRD) and radioluminescence (RL or X-ray luminescence) - photoluminescence (PL) –thermoluminescence (TL or TSL) - optical absorption spectrometry. The Tb3+ and Dy3+ ions were singly or doubly doped and the results were examined in detail. Moreover, for these phosphors, the energy transfer mechanisms which depend on RL and PL spectra were determined. The samples excited by X-ray demonstrate characteristic luminescence peaks of Dy3+ (422, 480, 575, 663 and 747 nm) and Tb3+ (489, 544, 586, 620, 652 and 675 nm). These emissions are similar for RL and PL measurements. It could be said that the energy transfer efficiency of the host material is perfect for rare-earth ions. The synthesized phosphors exhibit various colors from yellow to blue under UV excitation. The optical band gaps of host CLW, CLW: Tb3+, CLW: Dy3+ and co-doped CLW: Tb3+/Dy3+ were calculated at values 3.83 eV, 3.44 eV, 3.64 eV and 3.52 eV, respectively. From the results obtained, the CaLa2(WO4)4: Tb3+, Dy3+phosphors may be one of the potential candidates for light-emitting diode.  相似文献   

2.
《Ceramics International》2017,43(12):9084-9091
This paper reports the preparation of Eu3+ doped Gadolinium oxyorthosilicate (Gd2SiO5:Eu3+) phosphor with different concentration of Eu3+(0.1–2.5 mol%) using the modified solid state reaction method. The synthesis procedure of the Gd2SiO5:Eu3+phosphor using inorganic materials such as Gd2O3, silicon dioxide (SiO2), europium oxide (Eu2O3) and boric acid (H3BO3) as flux is discussed in detail. The prepared phosphor samples were characterized by using X-Ray Diffraction (XRD), Field Emission Gun Scanning Electron Microscopy (FEGSEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Photoluminescence (PL) and Thermoluminescence (TL). The Commission Internationale de l′Eclairage(CIE) coordinates were also calculated. The PL emission was observed in the 350–630 nm range for the Gd2SiO5:Eu3+ phosphor. PL excitation peaks were observed at 266, 275, 312 and 395 nm while the emission peaks were observed at 380, 416, 437, 545, 579, 589, 607, 615 and 628 nm. The emission peak at 615 nm was the most intense peak for all the different Eu3+ concentration samples. From the XRD data, using the Scherrer's formula, the average crystallite size of the Gd2SiO5:Eu3+ phosphor was calculated to be 33 nm. TL was carried out for the phosphor after both UV and gamma irradiation. The TL response of the Gd2SiO5:Eu3+ phosphor for the two different radiations was compared and studied in detail. It was found that the present phosphor can acts as a single host for red emission (1.5 mol%) for display devices and light emitting diode (LED) and white light emission for Eu3+(0.1 mol%) and it might be used as a TL dosimetric material for gamma dose detection.  相似文献   

3.
A model Pd/Fe2O3 catalyst prepared by the vacuum technique has been studied in the carbon monoxide oxidation in the temperature range of 300–550 K at reagent pressures P(CO)=16 Torr, P(O2)= 4 Torr. It has been shown that the activity of the fresh catalysts is determined by palladium. According to the XPS data, the reduction with carbon monoxide results in the formation of Fe2+ (formally Fe3O4) and appearance of the catalytic activity in this reaction at low temperatures (350 K). High low-temperature activity of the catalyst is supposed to be connected with the reaction between oxygen adsorbed on the reduced sites of the support (Fe2+) and CO adsorbed on palladium (COads) at the metal–oxide interface.  相似文献   

4.
《Ceramics International》2023,49(18):29690-29698
With the trend of electronic information technology towards miniaturization, integration and intelligence, higher requirements are put forward for the performance of dielectric ceramic materials. In this paper, a series of doped samples Sm2O3-xZnO (x = 0, 0.1, 0.2, 0.4, 0.6, 0.8) were successfully prepared by the traditional solid state reaction method, and the complex dielectric properties of the ceramic samples were investigated as a function of temperature (100 K–400 K) and frequency (102–106 Hz) separately. A new phase Zn6.76Sm2.58O10.6 was found in all samples, and all samples were complex. At a higher temperature, 350 K, with the increase of ZnO doping content, the maximum dielectric constant is 434.7, the dielectric loss is as low as 0.0098, and the dielectric performance is significantly increased compared with room temperature. UV–Vis DRS test showed that the absorbance of the sample increased with the increase of ZnO content, and the side reaction showed that the dielectric constant and dielectric loss of the sample were improved under the action of UV light. These provide an experimental basis for the application of samarium based dielectric ceramics.  相似文献   

5.
A laser melting method has been developed for the synthesis of highly luminescent, long-lasting SrAl2O4:Eu2+, Dy3+ phosphors. The high temperature achieved in high-power density CO2 laser irradiation of mixtures of SrCO3, Al2O3, Eu2O3, and Dy2O3 enabled the one-step, fast synthesis of these phosphors in air at atmospheric pressure. X-ray diffraction, Raman spectroscopy, and scanning electron microscopy characterization studies reveal that the produced materials consist of monoclinic SrAl2O4 grains extensively surrounded by rare-earth ion-enriched grain boundaries. The photoluminescence properties of laser-produced SrAl2O4:Eu2+, Dy3+ materials are discussed. The results reported here suggest that this laser melting method is a promising route for the synthesis of ceramic phosphors. It is presented as an alternative to the conventional sol–gel and solid-state methods, which require the use of high-temperature furnaces, flux additives, and reducing atmospheres.  相似文献   

6.
《Ceramics International》2020,46(8):11717-11725
Outdoor lighting and other lighting systems can disrupt natural plant growth habits. Thus, LED lighting that is not detrimental to plant growth is required. In our study, Dy3+-doped Ca8ZnY(PO4)7:Dy3+ phosphor with enhanced luminescence properties caused by the co-dopants Mg2+ and B3+ were synthesised. The samples had multiple excitation peaks, indicating they are excited by either near-ultraviolet (n-UV) or blue chips. All samples exhibited bright narrow yellow and blue emission corresponding to the transitions of Dy3+ ions with 4F9/26H13/2 and 4F9/26H13/2, respectively. Moreover, doping with Mg2+ and B3+ enhanced the luminescence intensity, reaching 113.6 and 119.7%, respectively. In addition, the luminescence emission intensity at 150 °C was maintained at approximately 95% of the initial value at 25 °C, and its thermal stability increased by 123%. Devices assembled with an n-UV chip (388 nm) and the as-obtained CZMYP:Dy3+ phosphor emitted a bright warm white light and simulated outdoor dark lighting for tobacco cultivation, indicating that the as-prepared phosphor is an excellent candidate material for plant habitat-conscious phosphors.  相似文献   

7.
《Ceramics International》2016,42(11):13004-13010
A series of Dy3+ or/and Eu3+ doped Y2Mo4O15 phosphors were successfully synthesized at a low temperature of 600 °C via solid state reaction. The as-prepared phosphors were characterized by X-ray powder diffraction (XRD), scanning electronic microscope (SEM), photoluminescence (PL) excitation, emission spectra and PL decay curves. XRD results demonstrate that Y2Mo4O15: Dy3+, Eu3+ has the monoclinic structure with the space group of p21/C(14). Under the excitation of ultraviolet (UV) or near-UV light, the Dy3+ and Eu3+ ions activated Y2Mo4O15 phosphors exhibit their characteristic emissions in the blue, yellow and red regions. The emitting light color of the Y2Mo4O15: 0.08Dy3+, yEu3+ phosphors can be adjusted by varying the concentration ratio of Dy3+ to Eu3+ ions and a white light is achieved when the doping concentration of Eu3+ is 5%. In addition, the energy transfer from Dy3+ to Eu3+ is also confirmed based on the luminescence spectra and decay curves.  相似文献   

8.
《Ceramics International》2022,48(12):17225-17233
In this study, we prepared a novel series of Li2xCu1-xMoO4 (x = 0.02, 0.04, 0.06, 0.08, and 0.10) microwave ceramics. The dynamic sintering behavior, crystal phases, micro-morphologies, and dielectric properties of the samples were studied. The substitution of Li+ contributed to refining the crystal grain size, promoting the densification of microstructure, and enhancing the quality factor. Due to different valence substitutions, Cu+ ions were created, which were verified by X-ray photoelectron spectroscopy (XPS) and Raman experiments. In addition, the Raman shift, full width at half maximum (FWHM) value of the A1g peak, and crystal microstrains were analyzed to gain a mechanistic understanding of the influence of structure on the dielectric properties. When x = 0.08, the Li2xCu1-xMoO4 ceramic sintered at 675 °C exhibited optimal comprehensive properties with εr = 8.17, Qf = 68 476 GHz, and τf = ?25 ppm/°C, and good chemical stability between the ceramic and Al electrode was also achieved. These promising properties make Li2xCu1-xMoO4 (x = 0.08) more suitable for ultra-low temperature co-fired ceramic (ULTCC) applications.  相似文献   

9.
《Ceramics International》2020,46(10):15943-15948
In this research work, we have investigated the structural development of Tb3+ and Dy3+ co-substituted CoFe2O4 ferrites using temperature and time dependent XRD measurements. Sol-gel auto combustion technique was used to synthesized Tb3+ and Dy3+ co-substituted spinel ferrites with composition CoFe2-x-y TbxDyyO4 (x + y = 0.0–0.25). Various characterization techniques such as High temperature XRD, XPS and SQUID were used to observe the Kinetics mechanism as well as the impact of co-substitution on the structural and magnetic properties. Room temperature XRD scans showed that the synthesized materials having single phase and were crystalline in nature. The crystallite size was lied in nano regime ranging from 26.07 to 21.92 nm and lattice parameters were found to be decreased with increasing rare earth metal ions contents. Temperature and time dependent XRD data suggested that structure of investigated samples not degrade even at temperature 900 °C which was maintained for 2 h. The ionic states of Co2+, Tb3+, Dy3+ and Fe3+ were confirmed by X-ray Photoelectron spectrometry measurements along with the binding energies of Co2p, Tb 2p, Dy 2p, Fe 2p which confirmed the tetrahedral and octahedral sites for substituted ions. Room temperature magnetic measurements of annealed nanoferrites were carried out by operating the SQUID magnetometer in VSM mode. The data demonstrated that increasing concentrations of substituent (Tb3+and Dy3+) resulted in the reduction of various magnetic parameters such as remanence, saturation magnetization and Coercivity. The calculated values of saturation magnetization and coercivities were found in the range of 78.1–45.15emu/g and 742–543Oe respectively. This study concluded that cation distribution and crystallite size is effective in controlling the structural, morphological and magnetic properties.  相似文献   

10.
《Ceramics International》2022,48(12):17157-17170
Pure pyrochlore Ca2Ti2O6, perovskite CaTiO3, and their mixed crystalline phases with different proportions were controllably synthesized via a solvothermal method, followed by a subsequent calcination process. RIR (reference intensity ratio) data of Ca2Ti2O6 were first obtained by X-ray diffraction (XRD), which can be used to quantitatively analyze the phase composition. When Eu3+ is doped into these calcium titanium oxides, they can be used as luminescent and photocatalytic materials. The structure, luminescence, and photocatalytic properties of pure pyrochlore Ca2Ti2O6:Eu3+ and perovskite CaTiO3:Eu3+ were comparatively studied in detail. The relative intensities of the excitation peaks and the emission peaks in Ca2Ti2O6:Eu3+ and CaTiO3:Eu3+ are different, which is attributed to the different symmetries of Eu3+ inhabiting the two kinds of lattices. In addition, although the luminescence intensity of CaTiO3:3%Eu3+ is higher than that of Ca2Ti2O6:3%Eu3+ under excitation at 394 nm, the luminescence intensity of Ca2Ti2O6:3%Eu3+ is superior to that of CaTiO3:3%Eu3+ under excitation at 464 nm and 533 nm. Photocatalytic experiments show that Ca2Ti2O6:3%Eu3+ has better photocatalytic performance than CaTiO3:3%Eu3+, which is mainly due to its smaller crystallite size, higher specific surface area and pyrochlore structure. In addition, biphase (Ca2Ti2O6–CaTiO3):3%Eu3+ has the best photocatalytic activity compared with the single phase Ca2Ti2O6:3%Eu3+ and CaTiO3:3%Eu3+, owing to the presence of heterojunctions that significantly reduced the band gap. It is anticipated that the discovery of this bifunctional Ca2Ti2O6:Eu3+ would expand the application of rare earth-doped calcium titanium oxide materials.  相似文献   

11.
Series of (1–9 mol %) dysprosium (Dy3+) ions doped MgNb2O6 (MNO) nanophosphors were synthesized by chemical combustion process and their photo luminescent and photocatalytic behaviours were examined. Powder X-ray diffraction (PXRD) reveals the columbite structure and crystal structure parameters were calculated. The average crystallite size was found to be in the range of 20–30 nm as calculated by Scherrer's method. The photoluminescence (PL) of MgNb2O6:Dy3+exc-393 nm) reflects white emission for the prepared samples as confirmed by CIE and CCT. The photocatalytic activities of these nanophosphors were probed for the decolorization of acid red 88 (AR-88) under UV light irradiation. The photocatalyst with MgNb2O6:Dy3+ (5 mol %) showed enhanced activity of 97%, attributed to effective separation of charge carriers. All the above experimental results confirm that, the optimized phosphor is quite useful for WLEDs, solid-state lighting applications and as a photocatalyst.  相似文献   

12.
Ti4+-activated zinc calcium aluminate phosphors, owing to their excellent luminescence properties, nontoxicity, environment friendliness and low price, have a certain prospect in the field of plant cultivation. In this study, we have successfully synthesized a series of Ca14-yAl10-xZn6-zO35:xTi4+ (CAZO:Ti4+) phosphors through a high-temperature solid-state method. Furthermore, the emission spectrum of CAZO:Ti4+ located in bluish violet-emitting band, and has an emission peak at 378?nm upon the excitation of 268?nm due to the charge transfer of Ti4+-O2-. Moreover, the luminescence intensity of as-synthetized phosphors can be improved by cation vacancies engineering to compensate for charge unbalance. Especially, the luminescence intensity could be further improved when the Ca2+ vacancy is 0.35?mol or the Zn2+ vacancy is 0.275?mol. Furthermore, the X-ray powder diffraction (XRD) analysis and crystal structure are checked and confirmed that the synthesized material is pure phase. The concentration quenching mechanism, FT-IR spectra, UV–vis absorption properties, lifetimes and electron transition process of Ca14-yAl10-xZn6-zO35: xTi4+ were discussed in detail. From the above, the phosphor has a potential application for plant growth field due to its broad bluish violet emission.  相似文献   

13.
《Ceramics International》2017,43(11):8406-8410
Color-tunable Dy3+/Eu3+ co-doped in Ce2AlO3N phosphors were synthesized via a simple conventional solid state reaction. The as-prepared samples were characterized by XRD, TEM and photoluminescence spectra. Results show that the concentrations of Eu3+ ions can affect the blue and yellow emission intensities of Dy3+, and tunable emission color can be obtained by adjusting the doping concentrations of Eu3+. Based on the energy levers of Eu3+and Dy3+, the mechanism of tunable color has been presented in detail. The thermal stability of Dy3+/Eu3+: Ce2AlO3N has also been discussed.  相似文献   

14.
In this study, ternary MWCNTs/CoFe2O4/FeCo nanocomposite coated with conductive PEDOT-polyaniline (PA@MW/F/C) co-polymers were synthesized by microwave-assisted sol-gel followed in-situ polymerization methods. The phases, crystal structures, morphologies, magnetic and electromagnetic features of the as-prepared samples were identified via XRD, SEM, XPS, VSM, and VNA respectively. Absorption characteristics were investigated in the frequency (12–18 GHz) Ku band. XRD, VSM and SEM analysis confirmed the partial reduction process of CoFe2O4 and successfully decorated magneto-dielectric particles with co-polymers. By measuring electromagnetic features of the samples, it was found that coating magneto-dielectric particles with conductive co-polymers improved the permittivity and dielectric constant, accordingly affecting the impedance matching characteristic and attenuation constant performance. Moreover, exchange coupling behavior was found significant impacts on the microwave absorption properties. PA@MW/F/C coated nanocomposite revealed the maximum reflection loss of ?90 dB at 13.8 GHz with 4 GHz effective bandwidth and 1.5 mm thickness. Due to the enhanced interfacial polarization, impedance matching and exchange coupling effects of the as-prepared nanocomposite, it owns excellent microwave absorption properties, which can be applied as an absorber with distinguishing features (strong absorption, thin thickness, and broadest effective bandwidth).  相似文献   

15.
《Ceramics International》2022,48(24):36110-36120
This study mainly focuses on the thermoluminescence features and trap parameter analysis of Sr2Al2SiO7:Dy3+ phosphors prepared via the low-temperature combustion method. The phase confirmation, structural and morphological studies are performed using XRD, FTIR, SEM and EDX characterizations. The energy gap of pure and Dy3+ doped phosphors is calculated. And the band gap decrease with doping. The optimum concentration was 3 mol% from the emission spectra; hence, this sample was irradiated with 3 Gy–5 kGy gamma doses. The samples showed high sensitivity and the MDD value is 0.21 mGy. The trap parameters were determined following deconvolution of the glow curves. Four traps were found in the samples, and the trap lifetime increased with increasing gamma dose. The trap depth increased The linear response from 3 Gy to 250 Gy implies that the prepared samples could be used as γ dosimeters within this range.  相似文献   

16.
《Ceramics International》2016,42(3):4019-4025
Terbium ion doped zinc aluminum phosphate (ZAP) glasses with composition (90−x)((90−y)P2O5–10Al2O3yZnO)–xTb2O3 (x=0.5–9 in mol% and y=30, 35, 40 in mol%) have been prepared by melt quenching method, and the effects of the Tb2O3 and ZnO content on the luminescence properties have been studied by photoluminescence spectroscopies. It was found that the green emission peaked at 544 nm is significantly enhanced under higher Tb2O3 content, meanwhile the sensitization effect of ZnO content is confirmed from the enhanced main emission. The quenching effect attributed to the resonant energy transfer through the cross-relaxation mechanism is observed when Tb2O3 concentration is beyond 2.5 mol% due to the fact that more Tb3+ ions enhance the 4f→5d and 4f→4f electronic transitions through the dipole–dipole (d–d) interaction. Also, ZnO plays a role of the disperser to prevent non-radiative de-excitation process. A characteristic luminescence image of the (100−x)(60P2O5–10Al2O3–30ZnO)·xTb2O3 series glasses under UV excitation at 366 nm is presented for the first time, and the transition of luminescence suggests that the Tb3+-doped ZAP glasses are suitable for green and dual-color blue/green LED applications by modulation of Tb and ZnO composition.  相似文献   

17.
《Ceramics International》2017,43(11):8378-8390
Dysprosium (Dy) substituted nickel ferrite (NiDyxFe2-xO4) powders with varying Dy content (x=0.0, 0.025, 0.05, 0.075, 0.1, 0.2) have been prepared by combustion method using DL-alanine fuel. Sintering characteristics of the powders and electrical properties of ceramics have been studied. Effective substitution of Dy3+ for Fe3+ is seen up to x=0.075 yielding improved properties, and a higher Dy content (x≥0.1) leads to partial substitution, disturbed stoichiometry, and diffusion of Dy to the grain boundaries and segregation as a secondary phase. Increasing Dy content reduces the crystallite size, powder particle size, and grain size in sintered ceramics, and the changing microstructural evolution is better resolved with back scattered electron imaging and compositional analysis. Raman spectroscopy confirms inverse spinel structure formation and substantiates the presence of secondary phase evidenced through X-ray diffraction and electron microscopy. A marginal increase in the electrical resistivity (ρdc) and magnetization are observed due to effectual substitution of Dy3+ for Fe3+ at the octahedral sites up to x=0.075. For x≥0.1, the increasing influence of highly resistive DyFeO3 secondary phase at the inter-granular boundaries leads to a rapid increase in resistivity and reduction in dielectric losses, and the magnetization is reduced due to the anti-ferromagnetic nature of the secondary phase (DyFeO3). Dense ceramics with high resistivity (~109 Ω cm), low dielectric loss (tan δ ~0.002) at 1 MHz, and high magnetization (50.07 emu/g) are obtained for an optimum Dy content of x=0.075. Dielectric response, complex impedance, and electrical modulus spectroscopy in the frequency range (10−2–106 Hz) reflect the changes in the microstructure, and suggests a non-Debye type relaxation.  相似文献   

18.
《Ceramics International》2015,41(7):8481-8487
In this work Sm3+ (0–2.0 at%) and Bi3+ (0–2.0 at%) doped Y2O3 luminescent powders were prepared by a sol–gel method from yttrium acetylacetonate, samarium and bismuth nitrates as metal sources. The as prepared powders (chemical composition is close to stoichiometric Y2O3) present the cubic structure from 700 °C, and at 900 °C are characterized by the presence of rounded particles with heterogeneous size of 42.9 nm. Luminescent effect of ions of Sm3+ and Bi3+ into Y2O3 host as was studied on heat treated powders from 800 to 1100 °C. The combination of the red luminescence from the Sm3+ ions and the bluish from Bi3+, makes the synthesized phosphors candidates to be used in fabrication of phosphor-converted light-emitting diodes (LEDs).  相似文献   

19.
A series of Ca5(PO4)3F:Dy3+, Eu3+ phosphors was synthesized by a solid‐state reaction method. The XRD results show that all as‐prepared Ca5(PO4)3F:Dy3+, Eu3+ samples match well with the standard Ca5(PO4)3F structure and the doped Dy3+ and Eu3+ ions have no effect on the crystal structure. Under near‐ultraviolet excitation, Dy3+ doped Ca5(PO4)3F phosphor shows blue (486 nm) and yellow (579 nm) emissions, which correspond to 4F9/26H15/2 and 4F9/26H13/2 transitions respectively. Eu3+ co‐doped Ca5(PO4)3F:Dy3+ phosphor shows the additional red emission of Eu3+ at 631 nm, and an improved color rendering index. The chromaticity coordinates of Ca5(PO4)3F:Dy3+, Eu3+ phosphors also indicate the excellent warm white emission characteristics and low correlated color temperature. Overall, these results suggest that the Ca5(PO4)3F:Dy3+, Eu3+ phosphors have potential applications in warm white light‐emitting diodes as single‐component phosphor.  相似文献   

20.
This study analyses the influence of Ni in the electrochemical behaviour of three different stainless steels in alkaline medium. The studied steels have increasing Ni content: AISI 430, AISI 304L and AISI 316. The obtained results are compared with those of a nickel base alloy (Ni > 42%, w/w) and a pure Ni electrode. Electrochemical impedance spectroscopy and cyclic voltammetry have been the main tools used to study the growth and evolution of the passive layers formed on those materials in alkaline medium. XPS and SEM have been employed for chemical and morphological characterization of the developed passive films.The presence of Ni promotes the formation of thinner and more protecting passive films. This fact noticed in the XPS analysis is reflected in the cyclic voltammograms by an important decrease of the magnetite formation peak current as well as that corresponding to Cr3+/Cr6+ oxidation. The low frequency limit of complex plane impedance plots also increases with the Ni content. In order to better characterise the resistivity of the electrochemically formed films, a more detailed impedance analysis in the high frequency range (1 kHz-10 MHz) has been performed. The analysis of the registered spectra indicates that Ni modifies the conductivity of the oxide layers, promoting the formation of more resistive oxide films.  相似文献   

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