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1.
Honghong Lei Yuncheng Zhou Peng Jiang Wei Wang Wenbin Cao Yawen Xue 《Ceramics International》2018,44(16):19751-19755
Cr-doped Ba2In2-xCrxO5+y (0?≤?x?≤?0.5) orange-brown inorganic oxides have been successfully synthesized by solid-state reaction. X-ray diffraction (XRD) patterns show that their crystal structures transform from orthorhombic to cubic by increasing the Cr doping amount. Field emission scanning electron microscopy (FESEM) measurements show powder particles of irregular shape with average particle size of about 10?µm. The colors of the compounds are tuned from light yellow (x?=?0) to orange (x?=?0.1) and then to dark brown (x?=?0.5). X-ray photoelectron spectroscopy and UV–Vis absorption spectroscopy demonstrate the oxidation state of Cr to be +?6 and the change in color to be due to the metal-ligand charge transfer of Cr6+-O2-. 相似文献
2.
《Ceramics International》2022,48(9):12415-12422
In this work, Ba3Ba1+xTa2-xO9-δ (x = 0, 0.1, 0.3, and 0.5) double perovskite proton conductors were prepared by solid-state reaction process. Phase compositions and microstructures were characterized by X-ray diffraction and field emission scanning electron microscope techniques. valence and semi-quantitative composition of components were identified by X-ray photoelectron spectroscopy. Conductivities of Ba3Ba1+xTa2-xO9-δ were then measured under various vapor and oxygen pressures by AC impedance spectroscopy technique. Results revealed linear increase in total conductivities of Ba3Ba1+xTa2-xO9-δ oxides as a function of temperature. Ba3Ba1.3Ta1.7O8.55 exhibited the highest total conductivity of 8.41 × 10?4 S cm?1 under humidity and 800 °C. The transport numbers calculated by defect equilibria model revealed. Ba3Ba1+xTa2-xO9-δ oxides as pure proton conductors at 400–800 °C. Also, transport numbers of oxide ions and holes both increased with temperature. Ba3Ba1.3Ta1.7O8.55 illustrated the highest protonic transport number of 0.60 at 800 °C. In sum, these results suggest that Ba3Ba1+xTa2-xO9-δ oxides display excellent proton conductivity. 相似文献
3.
《Ceramics International》2021,47(20):28487-28492
In this work, the microwave dielectric properties of Ba4(Nd1-yBiy)28/3Ti18-x(Al1/2Ta1/2)xO54(0≤x≤2, 0.05≤y≤0.2) ceramics co-substituted by A/B-site were studied. Firstly, (Al1/2Ta1/2)4+ was used for substitution at B-site. At 0≤x≤1.5, the above mentioned ceramic was found to exist in single-phase tungsten bronze structure, but at x = 2.0, the secondary phase appeared. Although the dielectric constant decreased by doping the (Al1/2Ta1/2)4+, but the quality factor was observed to improve by 40% and the temperature coefficient of resonant frequency decreased by 75%. Based on the above results, Bi3+ was introduced to Ba4Nd28/3Ti17(Al1/2Ta1/2)O54. The introduction of Bi3+ reduced the sintering temperature, greatly improved the dielectric constant, and ultimately decreased the temperature coefficient of resonant frequency, but it led to deterioration of quality factor. At last, with appropriate site-substitution content control (x = 1.0,y = 0.15), excellent comprehensive properties (εr = 89.0, Q × f = 5844 GHz @ 5.89 GHz,TCF = +8.7 ppm/°C) were obtained for the samples sintered at 1325 °C for 4 h. 相似文献
4.
Lan Wang Xiaoyan Shu Facheng Yi Dadong Shao Kuibao Zhang Haibin Zhang Xirui Lu 《Journal of the European Ceramic Society》2018,38(7):2863-2870
A series of Nd and Ce co-doped Gd2-xNdxZr2-yCeyO7 (0.0 ≤ x, y ≤ 2.0) ceramics were rapidly fabricated through spark plasma sintering (SPS) within 3?min. The effects of Nd and Ce contents on the phase composition, lattice parameter, active modes, microtopography and microstructure have been investigated in detail. XRD studies reveal that the compositions corresponding to 0.0 ≤ y ≤ 1.0 show a single phase and beyond 1.0 exhibit multiphase. The lattice parameters increase with elevated Nd and Ce content. The grains are densely packed on each other with cube-like shape, and the elements are almost homogeneously distributed in the compound. This synthetic method provides a simple pathway for the preparation of highly densified single phase ceramic at 1600–1700 ℃ for 3?min under pressure of 80?MPa. 相似文献
5.
《Journal of the European Ceramic Society》2021,41(15):7645-7653
We report the structure, dielectric, ferroelectric and piezoelectric properties of Cr-Mn co-doped (1-y)BiFe1-xCrxO3-yBaTi1-xMnxO3 (0≤x≤0.04, 0.2≤y≤0.27) ceramics. By varying both x and y, a series of samples near morphotropic phase boundaries exhibiting both high ferroelectric Curie temperature TC (∼580−643 °C) and relatively large piezoelectric constant d33 are constructed. Especially, the sample with y = 0.24 and x = 0.02 is found to show coexistence of high depolarization temperature Td (∼551 °C) and relatively large d33∼116 pC/N, superior to most of those of BiFeO3 based high-temperature piezoceramics reported previously. The enhanced ferroelectric TC in the Cr-Mn modified samples can be ascribed to the combined effects of large lattice distortion and high tetragonal phase content. These results demonstrate that constructing morphotropic phase boundaries via considering simultaneously the role of lattice distortion might be effective route to realize high-temperature and high piezoelectricity in BiFeO3-based systems. 相似文献
6.
《Journal of the European Ceramic Society》2000,20(5):625-630
Ceramic compacts in the systems Al2O3–Y2O3, Cr2O3–Y2O3 and Y3(CryAl1-y)5O12 (Cr-doped YAG) were prepared by solid state reaction in calcined co-precipitated powder mixtures of appropriate compositions. Various solid-solution phases were formed, e.g. Y3(Al1-xCrx)5O12, YAlyCr1-yO3 and Al2-xCrxO3. Composite materials in the pseudo-binary or ternary systems Al2O3–Y3Al5O12, Cr2O3–Y2O3 and Y3(Al1–xCrx)5O12–YAlyCr1–yO3–(AlzCr1−z)2O3 were obtained by hot-pressing appropriate powder precursors at 1600–1650°C for 1 h. The microstructure of the prepared materials was studied in a scanning electron microscope with element analysis facilities. X-ray diffraction was used to reveal the phases present and their lattice parameters. The chemical compatibility of these phases was investigated. The results are discussed with a special emphasis on the solubility of Cr in the YAG structure, and on the compatibility relationship between Cr-doped YAG and its neighbouring phases. A gel-coating process for preparing Al2O3–YAG composites with tailored microstructures is also described. 相似文献
7.
《Ceramics International》2021,47(24):34086-34091
Novel green and blue chromophores based on Ni/Co/Cr doped BaMg6Ti6O19 solid solutions are successfully synthesized through a solid-state reaction. The crystal structure of all the samples belongs to the magnetoplumbite structure with the space group of P63/mmc. The BaMg6-x/2Ti6-x/2NixO19 (0 ≤ x ≤ 0.3) compounds exhibit a light green (x = 0.1) to yellow-green (x = 0.3) color. The oxidation state of Ni is confirmed to be +2 valence and the d-d transition of Ni2+ in octahedral sites is responsible for color. BaMg6-x/2Ti6-x/2CoxO19 (0 ≤ x ≤ 0.3) series show a blue color and the intensity of blueness is increasing with the increase of Co content. The blue color is due to d-d transitions within Co2+ present in the tetrahedral sites. For BaMg6-x/2Ti6-x/2CrxO19 (0 ≤ x ≤ 2) phases the color varies from light green (x = 0.2) to green (x = 2). Chromium exists in +3 and + 6 oxidation states and the observed color is due to charge transfer transition between Cr3+–Ti4+ and d-d transitions within octahedral Cr3+ sites resulting in strong absorption in the visible region. The synthesized colored oxides are mixed with PMMA to prepare novel green and blue PMMA polymer composites to evaluate their compatibility in plastics. 相似文献
8.
《Ceramics International》2019,45(10):12942-12948
Sintering of oxides and carbonates at 1400 °C gives crystalline high-entropy single phase products with a BaFe12O19 (magnetoplumbite) structure containing 5 doping elements at high concentration level: Ba(Fe6Ti1·2Co1·2In1.2Ga1.2Cr1.2)O19. The complete list of explored substitutions includes K, Ca, Sr, Pb, La, Bi, Al, Ga, In, Ti, V, Cr, Mn, Co, and Ni. Loading to the batch more than 5 dopants or introduction of NiO, or V2O5 initiates formation of second phases like spinels or vanadates. Bi2O3 and K2O are too volatile at sintering temperature and were evaporated from the samples.Due to large ionic radius, the In3+ cation is likely to be incorporated not only on Fe3+ sites, but also on Ba2+ sites, that follow from resulting crystal composition. The smallest di-valent and tri-valent cations, Sr2+ and Al3+, are found to preferably concentrate together in the same magnetoplumbite phase crystals within one sample.According to elemental analysis of selected hexagonal crystals in the investigated 8 doped samples the most prospective compositions for obtaining high-entropy single phase with magnetoplumbite structure can be formulated as (Ca,Sr,Ba,Pb,La)Fex(Al,Ga,In,Ti,Cr,Mn,Co)12-xO19 where x = 1.5–6. 相似文献
9.
Kai Cheng Chunchun Li Changzhi Yin Ying Tang Yihua Sun Liang Fang 《Journal of the European Ceramic Society》2019,39(13):3738-3743
The effects of Sr2+ substitution for Ba2+ on microwave dielectric properties and crystal structure of Ba3-xSrx(VO4)2 (0 ≤ x ≤ 3, BSVO) solid solution were investigated. Such Sr2+ substitution contributes to significant reduction in sintering temperature from 1400 °C to 1150 °C. Both permittivity (∑r) and quality factor (Q × f) values decreased with increasing x value, which was determined to be related with the descending values of average polarizability and packing fraction, whereas the increase in τf value was explained by the decreased average VO bond length, A-site bond valence. BSVO ceramics possessed encouraging dielectric performances with ∑r = 12.2–15.6 ± 0.1, Q × f = 44,340 - 62,000 ± 800 GHz, and τf = 24.5–64.5 ± 0.2 ppm/°C. Low-temperature sintering was manipulated by adding B2O3 as sintering additive for the representative Sr3V2O8 (SVO) ceramic and only 1 wt.% B2O3 addition successfully contributed to a 21.7% decrease in sintering temperature to 900 °C, showing good chemical compatibility with silver electrodes, which render BSVO series and SVO ceramics potential candidates in multilayer electronic devices fabrication. 相似文献
10.
《Ceramics International》2023,49(18):29607-29613
The crystal structure of Ba2-xMgB2O6:xEu3+ phosphors, synthesized using a solid-state reaction, have been confirmed by X-ray diffraction analysis. This study focuses on the site occupancy preference of Eu3+ ions within the matrix, which was determined using bond energy theory, fluorescent spectra, and a consideration of energy transport and decay curves. The impact of Eu3+ ion concentration on luminescence has been assessed, and an optimal concentration (x = 0.22) identified. The critical distance, Rc was 9.6 Å, with a calculated θ value of 19.67, indicating that quadrupole-quadrupole interaction plays a critical role in the quenching Ba2-xMgB2O6:xEu3+ phosphors. The Ba2-xMgB2O6:xEu3+ phosphors exhibited a color purity of 99.26%, and a quantum efficiency of 49.68%. The activation energy Ea was determined to equal 0.2987 eV. The results have established Ba1.78MgB2O6:0.22Eu3+ as a red fluorescent powder with high quantum efficiency and a millisecond fluorescence lifetime. 相似文献
11.
《Ceramics International》2023,49(16):26675-26682
Phase formation, microstructure, magnetic properties, and dielectric properties of Ba1.5Sr1.5Co2Fe(23−x)CrxO41 (0.0 ≤ x ≤ 1.0) ceramics, in which Fe3+ ions were substituted by Cr3+ ions, were systematically investigated. X-ray diffraction results reveal that Z-type hexagonal ferrite was formed by sintering at 1250 °C, and Cr3+ ions successfully enter lattice without destroying crystal structure. Analysis of the microstructure reveals that Cr3+ ion doping has significant effect on crystal micromorphology. Samples with x = 0.4 have the most homogeneous micromorphology and the highest sintering density of 5.12 g/cm3. In addition, under the influence of external magnetic field, all samples exhibit typical soft magnetic character and hysteresis characteristics, with saturation magnetization up to 63.86 emu/g (x = 0.6). Particularly, compared with undoped sample, Cr-doped samples have outstanding magnetic–dielectric properties. Firstly, with increasing Cr3+ amount, real part of the permeability (μ′) reaches the maximum value of 10.70 at x = 0.4, while cutoff frequency exceeds 2 GHz, and Snoek constant reaches ∼19.50 GHz. Furthermore, due to more homogeneous microstructure, samples with x = 0.4 have low magnetic loss and can maintain high quality factor (Q) over a broad frequency range. Moreover, real part of the permittivity (ε′) reaches the maximum value of 16.90 at x = 0.6, and dielectric loss remains lower than 0.013 for frequencies below 0.7 GHz. Consequently, magnetic–dielectric materials prepared in this work are expected to have extensive application prospects for ultrahigh-frequency devices. 相似文献
12.
A series of Ba2Mg1−xMnxP4O13 (x = 0-1.0) and Ba1.94Eu0.06Mg1−xMnxP4O13 (x = 0-0.15) phosphors were prepared by conventional solid-state reaction. X-ray powder diffraction (XRD), the photoluminescence spectra, and the decay curves are investigated. XRD analysis shows that the maximum tolerable substitution of Mn2+ for Mg is about 50 mol% in Ba2MgP4O13. Mn2+-singly doped Ba2MgP4O13 shows weak red-luminescence peaked at about 615 nm. The Eu2+/Mn2+ co-doped phosphor emits two distinctive luminescence bands: a blue one centered at 430 nm originating from Eu2+ and a broad red-emitting one peaked at 615 nm from Mn2+ ions. The luminescence of Mn2+ ions can be greatly enhanced with the co-doping of Eu2+ in Ba2MgP4O13. The efficient energy transfer from Eu2+ to Mn2+ is verified by the excitation and emission spectra together with the luminescence decay curves. The emission colors could be tuned from the blue to the red-purple and eventually to the deep red. The resonance-type energy transfer via a dipole-quadrupole interaction mechanism is supported by the decay lifetime data. The energy transfer efficiency and the critical distance are calculated and discussed. The temperature dependent luminescence spectra of the Eu2+/Mn2+ co-doped phosphor show a good thermal stability on quenching effect. 相似文献
13.
《Ceramics International》2022,48(13):18784-18792
Bulk Cr1-xMnxO2 samples are prepared by high pressure synthesis technology. The crystal structure, magnetic properties and electronic structure of the samples are investigated by experiments and theoretical calculation. The crystal structure of the samples are indexed to a rutile structure with space group P42/mnm. The lattice parameter a of the samples remains basically unchanged in accordance with Vegard's law, but the lattice parameter c decreases due to increasing Mn dopant content (x) as well as strong Metal–Metal bonding along the c-axis. The saturation magnetization of the Cr1-xMnxO2 samples decreases with an increase in x. According to XPS analysis, there is electron transfer between Mn and Cr in Cr1-xMnxO2. Mn exists as Mn2+ and Mn3+ions, and part of Cr is oxidized to Cr6+. Based on the XPS analysis, the magnetic moment of Cr1-xMnxO2 is calculated and its value is in accordance with the experimental data. 相似文献
14.
《Ceramics International》2015,41(8):9873-9877
Solid solutions of In2−xScxW3O12 (0≤x≤2) were successfully synthesized using the solid state reaction method. Effects of substituted scandium content on the phase composition, microstructure, phase transition temperatures and thermal expansion behaviors of the resulting In2−xScxW3O12 (0≤x≤2) samples were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermal mechanical analyzer (TMA). Results indicate that the obtained In2W3O12 ceramic undergoes a structure phase transition from monoclinic to orthorhombic at 248 °C. This phase transition temperature of In2W3O12 can be easily shifted to a lower temperature by partly substituting the In3+ with Sc3+. When the x value increased from 0 to 1, the phase transition temperatures of In2−xScxW3O12 (0≤x≤2) samples decreased from 248 to 47 °C. All the In2−xScxW3O12 (0≤x≤2) ceramics show fine negative thermal expansion below their corresponding phase transition temperatures. The negative thermal expansion coefficients of the In2−xScxW3O12 (0≤x≤2) ceramics change in the range from −1.08×10−6 °C−1 to −7.13×10−6 °C−1. 相似文献
15.
L. P. Mezentseva V. E. Gasumyants O. A. Martynova O. A. Aleksandrova D. V. Potapov A. E. Lapshin 《Glass Physics and Chemistry》2006,32(3):374-379
Two series of yttrium cuprates Y0.8Ca0.2Ba2Cu3 ? y ZnyO7 ? δ (0 ≤ y ≤ 0.25) with isovalent substitutions and Y1 ? x CaxBa2Cu2.8Zn0.2O7 ? δ (0 ≤ x ≤ 0.25) with heterovalent substitutions are investigated. It is demonstrated that these compounds have an YBa2Cu3O7 ? δ-type structure in the orthorhombic crystal system. The isomorphous miscibility ranges and the concentration dependences of the unit cell parameters are determined for the solid solutions based on yttrium cuprates. The temperature dependences of the resistivity and the dependences of the critical temperature on the dopant concentration are analyzed. 相似文献
16.
《Ceramics International》2016,42(11):12843-12852
A novel lead-free, high dielectric constant, ultra-wide temperature stable dielectric ceramic Ba1−xBixTi1−x−yZn0.75xW0.25x+yO3+y (0.22≤x≤0.30, y=0.015) was synthesized by the traditional solid-state reaction method. The phase composition, electric and dielectric properties of the Ba1−xBixTi1−x−yZn0.75xW0.25x+yO3 ceramics were investigated. The P-V-L dielectric theory was introduced. And, the chemical bond energy was calculated to track the changes in micro-structure. The relationships between chemical bond energy and the macroscopic dielectric properties(εr, dielectric stability and dielectric loss) in Ba1−xBixTi1−x−yZn0.75xW0.25x+yO3+y ceramics were discussed systematically. Owing to the inhomogeneous micro-structure and the diffusion in phase transition, Ba1−xBixTi1−x−yZn0.75xW0.25x+yO3+y ceramics showed a stable permittivity (~800±15%) over a ultra-wide temperature range (−30 to 375 °C). Moreover, dielectric loss was less than 0.02 and the insulation resistance was over 1012 Ω cm. These features suggested that the Ba1−xBixTi1−x−yZn0.75xW0.25x+yO3+y ceramic could be considered as a promising candidate material for energy storage applications in harsh environment. 相似文献
17.
《Ceramics International》2020,46(2):1374-1382
The effects of Sr and Ca substitution of Ba on the Ba1.98-xSrx(Cax)MgSi2O7:Eu2+ photoluminescence properties have been investigated. The physical mechanisms for the photoluminescence variations are discussed. With Rietveld refinement method, the crystal structure of Ba1.98MgSi2O7:0.02Eu2+ and the lattice parameters of Sr and Ca substituted phosphors were refined. The emission band shift, the photoluminescence intensity variation, the phosphor chromaticity evolution, the Eu2+ lifetime distribution and the thermal stability elevation were investigated. With Sr and Ca substitution, the cell is shrinks. The cell shrinkage is resulting in the increase of the Eu2+ 5d electron crystal field splitting intensity, which is the reason for the emission band shift towards the long wavelength band. The photoluminescence intensity is increased firstly and then decreased. The intensity variation is the competitive result between the increase of the crystal structure rigidity and the rise of the lattice defect. The correlated color temperature can be cut down and the color purity can be adjusted. The photoluminescence life time of Eu2+ is raised firstly and then decreased. For Sr and Ca substitution, the thermal stability can be elevated. With the forbidden band gap calculation, the reason for the thermal stability elevation was investigated that for the substituted phosphors the forbidden band gap is enlarged and then limits the Eu2+ 5d self-ionization from the splitting levels to the conduction band. This work reveals that the Sr and Ca substitution of Ba can elevate the Ba1.98-xSrx(Cax)MgSi2O7:Eu2+ photoluminescence properties and improve the applications for the White Light Emitting Diode. 相似文献
18.
Yuqian Wang Honghong Lei Peng Jiang Lin Liu Kunyang Cui Wenbin Cao 《Ceramics International》2021,47(1):686-691
Mn-doped Ba7Al2-xMnxO10+y (0 ≤ x ≤ 0.7) samples with intense blue colors are successfully prepared by solid state reactions. With the increase of Mn content, the colors of compounds are tuned from cyan to ocean blue. FT-IR absorption spectrum and 27Al NMR spectrum indicate that the structure contains a dominating portion of Al–O tetrahedral sites while a small number of Al–O octahedral sites may also exist. The oxidation state of Mn is proved to be +5. Based on all the analysis, the intense blue shades of the samples are proposed as the d-d transition of Mn5+ ions in [AlO4] tetrahedral sites. 相似文献
19.
Longfei Yuan Wanbiao Hu Shaofan Fang Guangshe Li Xiyang Wang Xiaofeng Wu Wei Han Liping Li 《Journal of the European Ceramic Society》2018,38(15):4978-4985
Valence of Cu cations and Cu segregation of CdCu3Ti4O12 ceramics are initially examined by establishing the subsolidus phase diagram of Cd1-xCu3+x+2yTi4-yO12 (?7 ≤ x ≤ 0.07, ?1.333 ≤ y ≤ 2.91) systematically. Different from CaO-CuO-TiO2 system, the co-existence of hexagonal and orthorhombic CdTiO3 phases is observed in the line between CdTiO3 and CuO. Basing on the obtained phase diagram, three typical ceramics with Cu-equal (CdCu3Ti4O12), Cu-rich (Cd0.930Cu3.070Ti4O12), and Cu-poor (Cd1.137Cu2.863Ti4O12), showing high dielectric constant, are chosen as target samples to investigate the role of Cu valence and segregation in dielectric behaviors. Cu3+ ions, rather than Cu+ ones as reported previously, forms in the grain to act as the hopping charge carriers as demonstrated by X-ray photoelectron spectroscopy and High-energy X-ray absorption Near Edge Structure. This work would give a hint in tuning the stoichiometry for achieving more fascinating structures and properties in new ceramic material design. 相似文献
20.
Kang Du Chang-Zhi Yin Yan-Bo Guo Xiao-Chuan Wang Wen-Zhong Lu Shi-Wo Ta Chun-Yuan Hu Wen Lei 《Journal of the American Ceramic Society》2022,105(2):1253-1264
Ca3SnSi2-xGexO9 (0 ≤ x ≤ 0.8) and (1–y) Ca3SnSi1.6Ge0.4O9 – y CaSnSiO5 – 2 wt% LiF (y = 0.4 and 0.5) microwave dielectric ceramics were prepared by traditional solid-state reaction through sintering at 1250°C–1425°C for 5 h and at 875°C for 2 h, respectively. Ge4+ replaced Si4+, and Ca3SnSi2-xGexO9 (0 ≤ x ≤ 0.4) solid solutions were obtained. At 0.1 ≤ x ≤ 0.4, the Ge4+ substitution for Si4+ decreased the sintering temperature of Ca3SnSi2-xGexO9 from 1425 to 1300°C, the SnO6 octahedral distortions, and the average CaO7 decahedral distortions, which affected the τf value. The large average decahedral distortions corresponded with nearer-zero τf values at Ca3SnSi2-xGexO9 (0.1 ≤ x ≤ 0.4) ceramics. The τf value and sintering temperature of Ca3SnSi2-xGexO9 (x = 0.4) ceramic were adjusted to near-zero by CaSnSiO5 and decreased to 875°C upon the addition of 2 wt% LiF. The (1 – y) Ca3SnSi1.6Ge0.4O9 – y CaSnSiO5 – 2 wt% LiF (y = 0.5) ceramic sintered at 875°C for 2 h exhibited good microwave dielectric properties: εr = 10.3, Q × f = 14 300 GHz (at 12.2 GHz), and τf = ‒5.8 ppm/°C. 相似文献