We investigated the effect of annealing time on the structure and optical properties of Sr WO4：Eu^3＋ powders prepared by the non-hydrolytic sol-gel method and heat treated at 800 ℃ for 2,4,8 and 16 h.Thermogravimet...We investigated the effect of annealing time on the structure and optical properties of Sr WO4：Eu^3＋ powders prepared by the non-hydrolytic sol-gel method and heat treated at 800 ℃ for 2,4,8 and 16 h.Thermogravimetric and differential thermal analyses revealed that Sr WO4：Eu^3＋ powders were obtained at about 800 ℃.X-ray diffraction patterns and Rietveld refinement data confirmed that all powders had a scheelite-type tetragonal structure.Micro-Raman and Fourier transform infrared spectra indicated structural order at short range and anti-symmetric stretching vibrations of O-W-O bonds associated with tetrahedral[WO4]clusters.Optical properties were investigated by ultraviolet-visible（UV-vis）diffuse reflectance,and photoluminescence（PL）data which provided the evolution of quantum efficiency（η）and lifetime（τ）.UV-vis spectroscopy evidenced intermediate energy levels within the band gap of Sr WO4：Eu^3＋ powders.PL properties validated that the Eu^3＋ electric-dipole（^5D0→^7F2）transition in PL emission spectra was dominant which proved that Eu^3＋ ions were positioned in a site without an inversion center.[（^5D0→^7F2）/（^5D0→^7F1）]band ratios showed that Eu^3＋ ions were located in a low symmetry environment.The PL emission,ηandτproved the dependence on the annealing time in the behavior of Sr WO4：Eu3＋powders with a higher relative emission PL intensity as well as higherηandτvalues related to other samples when heat treated at 800℃ for 8 h.展开更多
This research reports the processing of magnesium matrix composites reinforced with silicon carbide(SiC)and aluminium oxide(Al_(2)O_(3))using powder metallurgy technique through high energy milling.Samples of Mg-SiC a...This research reports the processing of magnesium matrix composites reinforced with silicon carbide(SiC)and aluminium oxide(Al_(2)O_(3))using powder metallurgy technique through high energy milling.Samples of Mg-SiC and Mg-Al_(2)O_(3)composites subjected to high energy ball milling for different vol%of secondary particles 20,30 and 40%of SiC and Al_(2)O_(3)are studied by X-Ray diffraction technique.The rietveld method as implemented in the Fullprof program is applied in order to determine the quantities of the resulting crystalline phases and amorphous phases at each stage of the mechanical treatment.Microstructural examination is carried out using Scanning Electron Microscope(SEM).In addition,crystal structural analysis using appropriate size and strain models is performed in order to handle the distinctive anistrophy that is observed in convinced crystallographic directions for the magnesium composite.The results are furnished in terms of crystalline domains size enlargement of the magnesium composites phases upon prolonged milling duration and discussed in the light of up to date views and theories on crystal growth of nanocrystaline materials.The hardness of the composite samples is calculated by Vickers’s Hardness tester.Further,dry sling wear test and corrosion test are performed for the fabricated composites.Composite with 30%secondary particles incorporated magnesium composites exhibits better wear and corrosion resistance than the other composites.展开更多
Britholites with the general formula Ca10-xLnx（PO4）6-x（SiO4）xF2, （0≤x≤6） are considered to be promising matrices for the confinement of the by-products in the nuclear industry. A thermodynamic study showed tha...Britholites with the general formula Ca10-xLnx（PO4）6-x（SiO4）xF2, （0≤x≤6） are considered to be promising matrices for the confinement of the by-products in the nuclear industry. A thermodynamic study showed that the stability of these compounds de-creased as the substitution rate increased. The present work was an attempt to gain more information about the structural changes in-duced by the substitution, in order to understand the observed stability decrease. The samples were successfully synthesized as a sin-gle-phase apatite by a solid-state reaction between 1200 and 1400 °C. The structural refinement indicated that the La3＋ions preferen-tially occupied the 6（h） sites. A progressive shift of F-along the c-axis outside its ideal position occurred as a result of the substitution increase. This might be the cause of the observed stability decrease, especially as the energies of the La-O, La-F and Si-O bonds are higher than those of Ca-O, Ca-F and P-O. The distribution of La3＋ between the two non-equivalent sites was confirmed by the charge distribution method.展开更多
Strontium-britholites whose chemical formula was Sr10-xLax（PO4）6-x（SiO4）xF2, where x=0, 1, 2, and 4 were prepared by solid state reaction. The structural refinement carried out using the Rietveld method indicated ...Strontium-britholites whose chemical formula was Sr10-xLax（PO4）6-x（SiO4）xF2, where x=0, 1, 2, and 4 were prepared by solid state reaction. The structural refinement carried out using the Rietveld method indicated that La^3＋ ions were located into the two sites with a strong preference for metal （2） sites especially for low contents. A progressive shift of the F position along the c-axis outside the centre of the triangle formed by metal （2）-atoms was observed with the increase of x. The infrared and Raman spectra exhibited the characteristic vibration modes of PO4 and SiO4groups confirming the incorporation of this last group into the apatite structure. The 295i MAS-NMR spectra exhibited one resonance peak confirming the data obtained by X-ray diffraction, indicating that P and Si were located in the same crystallographic site.展开更多
Fe_(81)Al_(19) polycrystalline alloys doped with Tb(0-0.25 at%) were obtained by arc melting.The introduction of Tb favors the formation of columnar grains in the micro structure of the alloys,which develops a texture...Fe_(81)Al_(19) polycrystalline alloys doped with Tb(0-0.25 at%) were obtained by arc melting.The introduction of Tb favors the formation of columnar grains in the micro structure of the alloys,which develops a texture in the [100]crystal direction.Microstructural examination shows that the alloys are composed in great proportion by the disordered body-centered cubic(bcc),A2 phase and by a small proportion of the ordered bcc,B2 phase.As a consequence of doping with Tb,the lattice parameter increases,so the calculated apparent crystallite size increases,indicating a decrease in dislocation density and therefore in microstrains.The change in the magnetostriction with the magnetic field,dλ_(T)/dH,is directly related to strain anisotropy that can favor the iron easy magnetization axis on the [100] direction.An increase in total magnetostriction is found in the doped alloys with a maximum of 90 × 10^(-6) at 300 K for the alloy containing 0.027 at% Tb.This enhancement is a threefold value of the undoped alloy,which is attributed to the smaller maximum strain value and the preferential orientation formation by the columnar grains.展开更多
The X-ray diffraction analyses show that the existence of a continuous solid solution of Al_xSb_ 3-xY_5 (0≤x≤216). Al_xSb_ 3-xY_5 crystallizes in the hexagonal system with the space group P6_3/mcm (193) and Mn_5Si_3...The X-ray diffraction analyses show that the existence of a continuous solid solution of Al_xSb_ 3-xY_5 (0≤x≤216). Al_xSb_ 3-xY_5 crystallizes in the hexagonal system with the space group P6_3/mcm (193) and Mn_5Si_3 structure type. The cell parameters for Al_2SbY_5 compound at 25 ℃ are a=0.88086 (2) nm, c=0.64662 (2) nm.展开更多
The phase of pyrochlore Gd_2Zr_2O_7 used for immobilization of Pu （Ⅳ） was investigated, tetravalent cerium was used as the simulacrum for plutonium with tetravalence, and the compounds in the system Gd_2Zr_2-_xCe_x...The phase of pyrochlore Gd_2Zr_2O_7 used for immobilization of Pu （Ⅳ） was investigated, tetravalent cerium was used as the simulacrum for plutonium with tetravalence, and the compounds in the system Gd_2Zr_2-_xCe_xO_7 （0.0≤x≤2.0） were synthesized via a high temperature solid reaction method with Gd_2O_3 and ZrO_2 powders being used as the starting materials. Based on the collected XRD data of the gained samples, the phase and microstructural change of compounds were calculated by means of rietveld structural refinement method. The experimental results indicated that the phases of compounds were changed from pyrochlore to fluorite-type phase with the increasing x. The linear relation between a and x was discovered in the range of fluorite-type phase, which accorded with a = 0.52748 ＋ 0.00825 x （0.2≤x≤2.0）, while V= 0.14668 ＋ 0.00711 x （0.2≤x≤2.0） was also achieved.展开更多
Layered lithium transition metal oxide(LTMO)cathode materials have attracted much attention for lithium-ion batteries and are shining in the current market.Establishing a clear structure-performance relationship is ne...Layered lithium transition metal oxide(LTMO)cathode materials have attracted much attention for lithium-ion batteries and are shining in the current market.Establishing a clear structure-performance relationship is necessary for the performance improvement of LTMO cathode materials.The combination of synchrotron X-ray diffraction(XRD)with high intensity and XRD Rietveld refinement is powerful for revealing the structural characteristics of LTMO cathode materials.This review summarizes the application of high energy XRD and Rietveld refinement in LTMO cathode materials,including the brief introduction of synchrotron XRD and Rietveld refinement and their applications in understanding the structural evolution related to the synthetic,thermal runaway,cycling,and high-rate charge/discharge process of LTMO cathode materials.Synchrotron XRD can provide insights into the intermediates and reaction paths in the synthesis process,the origin of thermal runaway,the mechanism of structural decay during cycles,and the structural evolution during high-rate charging/discharging.Future works should focus on the development of higher intensity X-rays to gain more in-depth insights into the intrinsic relationship between their structural characteristics and properties.展开更多
The compound CeNi 5Sn was studied by means of X ray powder diffraction technique and refined by Rietveld method. It has a hexagonal structure with space group P 6 3/ mmc (No.194), Z =4, the lattice constant...The compound CeNi 5Sn was studied by means of X ray powder diffraction technique and refined by Rietveld method. It has a hexagonal structure with space group P 6 3/ mmc (No.194), Z =4, the lattice constants a =0 48912(3) nm, c =1 973(2) nm and D x=8 974 g·cm -3 . The Rietveld structural refinement was performed, leading to R p=0 138 and R wp =0 185. The figure of merit F N for the XRD data is F 30 =82 1(0 0068, 54). The X ray powder diffraction data are presented.展开更多
オ-ray powder diffraction data and crystal structure of RE compound NdCoGe3 were studied by using X-ray powder diffraction and refined by the Rietveld profile fitting method. The compound has the tetragonal BaNiSn3typ...オ-ray powder diffraction data and crystal structure of RE compound NdCoGe3 were studied by using X-ray powder diffraction and refined by the Rietveld profile fitting method. The compound has the tetragonal BaNiSn3type structure, space group I4mm (No.107) a=0.42961(2) nm, c=098147(4) nm, V=0.018114 nm3, Z=2 and Dx=7.717 g·cm-3. The figure of merit FN for the powder data is F30=623 (0.0107, 45). Structure refinement was performed with 110 reflections and led to Rp=11.78% and Rwp=16.56%.展开更多
A new ternary Mg_(1.4)Co_(21.6)B_(6) compound in the Mg-Co-B system was synthesized via a conventional solid-state reaction method and the effect of Ni-substitution on its crystal structure,thermal stability,solid sol...A new ternary Mg_(1.4)Co_(21.6)B_(6) compound in the Mg-Co-B system was synthesized via a conventional solid-state reaction method and the effect of Ni-substitution on its crystal structure,thermal stability,solid solubility and physical properties were systematically investigated.The crystal structure of the Mg_(1.4)Co_(21.6)B_(6) compound was fully determined by the X-ray diffraction technique with Rietveld refinement method.It is found that Mg_(1.4)Co_(21.6)B_(6) crystallizes in the form of C_(6)Cr_(23) structure type(space group:Fm-3m(No.225),a=10.5617(2)A,Z=4).The results showed that the 4a sites have been occupied completely by Co atoms in present compound which with M_(2-x)Ni_(21+x)B_(6) form belonging to the W_(2)Cr_(21)C_(6)-type.When Mg_(1.4)Co_(21.6)B_(6) is repeatedly sintered at elevated temperatures,it becomes unstable and decomposes into Co3B and Mg.The lattice parameters of the Mg_(1.4)Co_(21.6)B_(6) solid solution alters dramtically with increasing Ni substitution,with no regular trend being observed.The electrical and magnetic performances of the 3.6Mg:3Co:17Ni:6B and 3.6Mg:3Co:18Ni:6B(nominal compositions)samples suggest that both samples are typical ferromagnetic materials.The temperature in the maximum drop of theρ(T)curve decreases as a function of the Ni content.Base on the correlation between the critical temperature and Ni content,a linear fitting equation is obtained and the critical temperature of Mg_(1.4)Co_(21.6)B_(6) calculated utilizing the linear fitting equation.The findings in this work may provide certain reference values for material science on electrical magnetic properties and other references for researching the material further.展开更多
Ce Y samples with different cerium（Ce） ions initial distribution were prepared by diverse preparation processes. The correlative influence of Ce ions distribution on the intracrystalline structure and catalytic mech...Ce Y samples with different cerium（Ce） ions initial distribution were prepared by diverse preparation processes. The correlative influence of Ce ions distribution on the intracrystalline structure and catalytic mechanism of Y-type zeolite was studied by X-ray diffraction（XRD）, Rietveld refinement, X-ray fluorescence spectrometry（XRF）, energy-dispersive X-ray spectroscopy（EDS）, infrared（IR） spectra, NH3 temperature-programmed desorption（NH3-TPD）, N2 physical adsorption-desorption and micro-activity test（MAT）. The results indicated that Ce ions were concentrated on the surface（supercage） of Ce Y zeolite would reduce the number of acid sites and the ratio of Br？nsted acid and Lewis acid（B/L）. Once Ce ions concentrated in the sodalite cage, it would participate in the coordination with framework oxygen atoms under the condition of steric hindrance. Meanwhile, Ce ions would preferentially promote the B/L value of weak acid by retaining more intracrystalline framework Al atoms in sodalite cage, which was beneficial to the conversion of heavy oil in FCC process. The optimal initial-distribution of Ce ions could not only save the consumption of rare earth resources but also give the best catalytic performance of Ce Y zeolite catalysts, and these advantages and attributes enabled it to have the potential to be applied in industrial applications.展开更多
LiNi0.8Co0.1Mn0.1O2 was prepared by a chloride co-precipitation method and characterized by thermogravimetric analysis, X-ray diffractometry with Rietveld refinement,electron scanning microscopy and electrochemical me...LiNi0.8Co0.1Mn0.1O2 was prepared by a chloride co-precipitation method and characterized by thermogravimetric analysis, X-ray diffractometry with Rietveld refinement,electron scanning microscopy and electrochemical measurements.Effects of lithium ion content and sintering temperature on physical and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 were also investigated. The results show that the sample synthesized at 750℃with 105%lithium content has fine particle sizes around 200 nm and homogenous sizes distribution.The initial discharge capacity for the powder is 184 mA·h/g between 2.7 and 4.3 V at 0.1C and room temperature.展开更多
The nanocrystalline samarium substituted Co-Zn ferrites with chemical formula Co0.7Zn0.3SmyFe2-yO4(where y=0,0.01,0.02,0.03,0.04) were synthesized by sol-gel autocombustion route.The analysis of Xray diffractograms(XR...The nanocrystalline samarium substituted Co-Zn ferrites with chemical formula Co0.7Zn0.3SmyFe2-yO4(where y=0,0.01,0.02,0.03,0.04) were synthesized by sol-gel autocombustion route.The analysis of Xray diffractograms(XRD) reveals the formation of cubic spinel structure.The planes indexed from XRD analyses were confirmed in the selected area electron diffraction(SAED) image of the sample.Nanocrystalline nature of the particles in the ferrite samples was confirmed by TEM.The morphology was analyzed by scanning electron microscopy(SEM).Magnetic measurements show an increase in the magnetization for x ≤0.03.The decrease in magnetization due to spin canting is observed for x=0.04.The coercivity depends on Sm3+doping concentration,grain size and saturation magnetization.The complex permeability of the ferrites was analyzed as the function of frequency and Sm3+composition(y).The real part of complex permeability varies linearly with the grain size.展开更多
An eco-friendly,new,and controllable approach for the preparation of manganese oxide(a-MnO_(2))nanorods has been introduced using hydrothermal reaction for supercapacitor application.The in-depth crystal structure ana...An eco-friendly,new,and controllable approach for the preparation of manganese oxide(a-MnO_(2))nanorods has been introduced using hydrothermal reaction for supercapacitor application.The in-depth crystal structure analysis ofα-MnO_(2) is analyzed by X-ray Rietveld refinement by using Full Prof program with the help of pseudo-Voigt profile function.The developed a-MnO_(2) electrode attains a remarkable capacitance of 577.7 F/g recorded at a current density value of 1 A/g with an excellent cycle life when is used for 10,000 repeated cycles due to the porous nanorod-morphology assisting the ease penetration of electrolyte ions into the electroactive sites.The diffusive and capacitive contributions of the electrode have been estimated by considering standard numerical packages in Python.After successfully assembling the aqueous symmetric supercapacitor(SSC)cell by utilizing the as-preparedα-MnO_(2),an excellent capacitance of 163.5 F/g and energy density of 58.1 Wh/kg at the constant current density of 0.5 A/g are obtained with an expanded potential frame of 1.6 V.Moreover,the cell has exceptionally withstood up to 10,000 cycles with an ultimate capacitance retention of 94.1%including the ability to light an LED for 18 s.Such findings recommend the developed a-MnO_(2) electrode to be a highly felicitous electrode for the field of energy storage.展开更多
Doped and undoped TiCh nanoparticles were prepared by Stober method and thermally treated at 600 ℃.The effect of Nd^（3＋） ion on the structure and micro structure of anatase-phase TiCh nanocrystals was studied by R...Doped and undoped TiCh nanoparticles were prepared by Stober method and thermally treated at 600 ℃.The effect of Nd^（3＋） ion on the structure and micro structure of anatase-phase TiCh nanocrystals was studied by Rietveld refinement method using X-ray powder diffraction data.Bond lengths,bond angles,and edges distances were analyzed.The phase formation was confirmed by high-resolution transmission electron microscopy.The adjustment of Ti-0 bond length induced by the addition of Nd^（3＋） ions,reduced the octahedral distortion and altered the octahedral array in the anatase-phase TiCh nanocrystal.The changes of structure and microstructure were mainly observed for TiCh nanoparticles doped with 0.1 at.%of Nd^（3＋） ions and attributed to the cationic substitution of Ti^（4＋） ions which promoted changes in the density of states and gap band of TiCh.The dopant insertion resulted in a better structural stability of the nanocrystals that enhanced their charge transference and photocatalytic efficiency.展开更多
The double perovskite oxide barium erbium niobate, Ba2ErNbO6 （BEN） was synthesized by solid state reaction technique. Rietveld refinement of the X-ray diffraction pattern of the sample showed cubic （Fm3m） phase at...The double perovskite oxide barium erbium niobate, Ba2ErNbO6 （BEN） was synthesized by solid state reaction technique. Rietveld refinement of the X-ray diffraction pattern of the sample showed cubic （Fm3m） phase at room temperature. Fourier trans-form infrared spectrum showed two primary phonon modes of the sample at around 387 and 600 cm-1. Raman spectrum of the sam-ple taken at 488 nm excitation wavelength showed four primary strong peaks at 106, 382, 747 and 814 cm-1. Lorentzian lines with 10 bands were used to fit the Raman spectrum. A group theoretical study was performed to assign all the Raman modes. Impedance spectroscopy was applied to investigate the ac electrical conductivity of BEN in a temperature range from 303 to 673 K and in a fre-quency range from 100 Hz-1 MHz. The dielectric relaxation mechanism was discussed in the frame work of permittivity, conduc-tivity, modulus and impedance formalisms. The complex plane plot of the impedance data was modeled by an equivalent circuit con-sisting of two serially connected R-CPE units, （one for the grain and the other for the grain boundary）, each containing a resistor （R） and a constant phase element （CPE）. The R-CPE units were used to incorporate the non-ideal character of the polarization phenome-non instead of an ideal capacitive behaviour. The relaxation time corresponding to dielectric loss was found to obey the Arrhenius law with activation energy of 0.85 eV. The frequency dependent conductivity spectra followed the Jonscher power law. The Cole-Cole model was used to investigate the dielectric relaxation mechanism in the sample.展开更多
Two compounds, Dy_2(WO_4)_3 and GdY(WO_4)_3, were synthesized by using thestandard solid state reaction technique. The crystal structure was determined by powder X-raydiffraction and Rietveld refinement method. It is ...Two compounds, Dy_2(WO_4)_3 and GdY(WO_4)_3, were synthesized by using thestandard solid state reaction technique. The crystal structure was determined by powder X-raydiffraction and Rietveld refinement method. It is found that both compounds have Eu_2(WO_4)_3-typemonoclinic structure, with space group C 2/c, Z = 4. The unit cell parameters of Dy_2(WO_4)_3 are a= 0.75981(1) nm, b = 1.13220(1) nm, c = 1.13254(1) nm, and beta = 109.8001(3) deg, and those ofGdY(WO_4)_3 arc a = 0.76175(1) nm, b = 1.13543(1) nm, c = 1.13496(2) nm, and beta = 109.8015(13)deg. Each W atom has four oxygen nearest neighbors, while each rare-earth atom is surrounded byeight oxygen atoms. WO_4 tetrahedra share their four vertices with REO_8 (RE = Dy, Gd, or Y)trigondodecahedra and some REO_8 trigondodecahedra share an edge with each other. The phasetransition and the magnetic properties were investigated by differential thermal analysis (DTA) anddc superconducting quantum interference device (SQUID) magnetometer.展开更多
Upconversion （UC） phosphor Tm3＋ doped YF3 nano-erystals were prepared by hydrothermal method under different conditions and characterized by Field Transmission electron microscopy （TEM）, Scanning electron microsc...Upconversion （UC） phosphor Tm3＋ doped YF3 nano-erystals were prepared by hydrothermal method under different conditions and characterized by Field Transmission electron microscopy （TEM）, Scanning electron microscopy （SEM） and X-ray diffraction （XRD）. Their UC luminescence properties were studied by fluorescence spectrophotometer with 980 nm diode laser excitation, and impact of different grain sizes and morphology on the UC luminescence intensity was discussed. The fluorescence decay lifetime was calculated by Multi-exponential function fitting method. Results show that UC emission intensity was enhanced with the reduction of grain size, and the decay lifetime is 0.60 us.展开更多
Specimens of Pb1-1.5xLax（Zr0.53 Ti0.47）1-y-zFeyNb2O3 （x = 0, 0.004, 0.008, 0.012, and 0.016, y = z = 0.01） （PZTFN） ceramics were synthesized by a semi-wet route. In the present study, the effect of La doping was...Specimens of Pb1-1.5xLax（Zr0.53 Ti0.47）1-y-zFeyNb2O3 （x = 0, 0.004, 0.008, 0.012, and 0.016, y = z = 0.01） （PZTFN） ceramics were synthesized by a semi-wet route. In the present study, the effect of La doping was investigated on the structural, microstructural, dielectric, piezoelectric, and ferroelectric properties of the ceramics. The results show that, the tetragonal （space group P4mm） and rhombohedral （space group R3c） phases are observed to coexist in the sample at x = 0.012. Microstructural investigations of all the samples reveal that La doping inhibits grain growth. Doping of La into PZTFN improves the dielectric, ferroelectric, and piezoelectric properties of the ceramics. The hys- teresis loops of all specimens exhibit nonlinear behavior. The dielectric, piezoelectric and ferroelectric properties show a maximum response atx 〉 0.012, which corresponds to the morphotropic phase boundary （MPB）.展开更多
基金Project supported by Brazilian Research Financing Institutions:Conselho Nacional para o Desenvolvimento de Pesquisa(CNPq) (142760/2008-0479644-2012-8+1 种基金 Postdoctoral 160922/2012-7)Fundacao para o Amparo a Pesquisa do Estado de S?o Paulo (FAPESP), and Conselho de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)
文摘We investigated the effect of annealing time on the structure and optical properties of Sr WO4：Eu^3＋ powders prepared by the non-hydrolytic sol-gel method and heat treated at 800 ℃ for 2,4,8 and 16 h.Thermogravimetric and differential thermal analyses revealed that Sr WO4：Eu^3＋ powders were obtained at about 800 ℃.X-ray diffraction patterns and Rietveld refinement data confirmed that all powders had a scheelite-type tetragonal structure.Micro-Raman and Fourier transform infrared spectra indicated structural order at short range and anti-symmetric stretching vibrations of O-W-O bonds associated with tetrahedral[WO4]clusters.Optical properties were investigated by ultraviolet-visible（UV-vis）diffuse reflectance,and photoluminescence（PL）data which provided the evolution of quantum efficiency（η）and lifetime（τ）.UV-vis spectroscopy evidenced intermediate energy levels within the band gap of Sr WO4：Eu^3＋ powders.PL properties validated that the Eu^3＋ electric-dipole（^5D0→^7F2）transition in PL emission spectra was dominant which proved that Eu^3＋ ions were positioned in a site without an inversion center.[（^5D0→^7F2）/（^5D0→^7F1）]band ratios showed that Eu^3＋ ions were located in a low symmetry environment.The PL emission,ηandτproved the dependence on the annealing time in the behavior of Sr WO4：Eu3＋powders with a higher relative emission PL intensity as well as higherηandτvalues related to other samples when heat treated at 800℃ for 8 h.
文摘This research reports the processing of magnesium matrix composites reinforced with silicon carbide(SiC)and aluminium oxide(Al_(2)O_(3))using powder metallurgy technique through high energy milling.Samples of Mg-SiC and Mg-Al_(2)O_(3)composites subjected to high energy ball milling for different vol%of secondary particles 20,30 and 40%of SiC and Al_(2)O_(3)are studied by X-Ray diffraction technique.The rietveld method as implemented in the Fullprof program is applied in order to determine the quantities of the resulting crystalline phases and amorphous phases at each stage of the mechanical treatment.Microstructural examination is carried out using Scanning Electron Microscope(SEM).In addition,crystal structural analysis using appropriate size and strain models is performed in order to handle the distinctive anistrophy that is observed in convinced crystallographic directions for the magnesium composite.The results are furnished in terms of crystalline domains size enlargement of the magnesium composites phases upon prolonged milling duration and discussed in the light of up to date views and theories on crystal growth of nanocrystaline materials.The hardness of the composite samples is calculated by Vickers’s Hardness tester.Further,dry sling wear test and corrosion test are performed for the fabricated composites.Composite with 30%secondary particles incorporated magnesium composites exhibits better wear and corrosion resistance than the other composites.
文摘Britholites with the general formula Ca10-xLnx（PO4）6-x（SiO4）xF2, （0≤x≤6） are considered to be promising matrices for the confinement of the by-products in the nuclear industry. A thermodynamic study showed that the stability of these compounds de-creased as the substitution rate increased. The present work was an attempt to gain more information about the structural changes in-duced by the substitution, in order to understand the observed stability decrease. The samples were successfully synthesized as a sin-gle-phase apatite by a solid-state reaction between 1200 and 1400 °C. The structural refinement indicated that the La3＋ions preferen-tially occupied the 6（h） sites. A progressive shift of F-along the c-axis outside its ideal position occurred as a result of the substitution increase. This might be the cause of the observed stability decrease, especially as the energies of the La-O, La-F and Si-O bonds are higher than those of Ca-O, Ca-F and P-O. The distribution of La3＋ between the two non-equivalent sites was confirmed by the charge distribution method.
基金the Ministry of Higher Education, Scientific Research and Technology (Tunisian)
文摘Strontium-britholites whose chemical formula was Sr10-xLax（PO4）6-x（SiO4）xF2, where x=0, 1, 2, and 4 were prepared by solid state reaction. The structural refinement carried out using the Rietveld method indicated that La^3＋ ions were located into the two sites with a strong preference for metal （2） sites especially for low contents. A progressive shift of the F position along the c-axis outside the centre of the triangle formed by metal （2）-atoms was observed with the increase of x. The infrared and Raman spectra exhibited the characteristic vibration modes of PO4 and SiO4groups confirming the incorporation of this last group into the apatite structure. The 295i MAS-NMR spectra exhibited one resonance peak confirming the data obtained by X-ray diffraction, indicating that P and Si were located in the same crystallographic site.
文摘Fe_(81)Al_(19) polycrystalline alloys doped with Tb(0-0.25 at%) were obtained by arc melting.The introduction of Tb favors the formation of columnar grains in the micro structure of the alloys,which develops a texture in the [100]crystal direction.Microstructural examination shows that the alloys are composed in great proportion by the disordered body-centered cubic(bcc),A2 phase and by a small proportion of the ordered bcc,B2 phase.As a consequence of doping with Tb,the lattice parameter increases,so the calculated apparent crystallite size increases,indicating a decrease in dislocation density and therefore in microstrains.The change in the magnetostriction with the magnetic field,dλ_(T)/dH,is directly related to strain anisotropy that can favor the iron easy magnetization axis on the [100] direction.An increase in total magnetostriction is found in the doped alloys with a maximum of 90 × 10^(-6) at 300 K for the alloy containing 0.027 at% Tb.This enhancement is a threefold value of the undoped alloy,which is attributed to the smaller maximum strain value and the preferential orientation formation by the columnar grains.
文摘The X-ray diffraction analyses show that the existence of a continuous solid solution of Al_xSb_ 3-xY_5 (0≤x≤216). Al_xSb_ 3-xY_5 crystallizes in the hexagonal system with the space group P6_3/mcm (193) and Mn_5Si_3 structure type. The cell parameters for Al_2SbY_5 compound at 25 ℃ are a=0.88086 (2) nm, c=0.64662 (2) nm.
基金Funded Partly by the Key Project of National High Technology Research and Development Program-"863"Program(No.2009AA050703)the National Natural Science Foundation of China(Nos.41302028,41272050,and 21007052)the Open Foundation of Joint Laboratory for Extreme Conditions Matter Properties,Southwest University of Science and Technology and Research Center of Laser Fusion,CAEP(No.12zxjk04)
文摘The phase of pyrochlore Gd_2Zr_2O_7 used for immobilization of Pu （Ⅳ） was investigated, tetravalent cerium was used as the simulacrum for plutonium with tetravalence, and the compounds in the system Gd_2Zr_2-_xCe_xO_7 （0.0≤x≤2.0） were synthesized via a high temperature solid reaction method with Gd_2O_3 and ZrO_2 powders being used as the starting materials. Based on the collected XRD data of the gained samples, the phase and microstructural change of compounds were calculated by means of rietveld structural refinement method. The experimental results indicated that the phases of compounds were changed from pyrochlore to fluorite-type phase with the increasing x. The linear relation between a and x was discovered in the range of fluorite-type phase, which accorded with a = 0.52748 ＋ 0.00825 x （0.2≤x≤2.0）, while V= 0.14668 ＋ 0.00711 x （0.2≤x≤2.0） was also achieved.
基金This work was supported by the National Natural Science Foundation of China(Nos.22121005,22020102002,and 21835004)the Frontiers Science Center for New Organic Matter of Nankai University(No.63181206).
文摘Layered lithium transition metal oxide(LTMO)cathode materials have attracted much attention for lithium-ion batteries and are shining in the current market.Establishing a clear structure-performance relationship is necessary for the performance improvement of LTMO cathode materials.The combination of synchrotron X-ray diffraction(XRD)with high intensity and XRD Rietveld refinement is powerful for revealing the structural characteristics of LTMO cathode materials.This review summarizes the application of high energy XRD and Rietveld refinement in LTMO cathode materials,including the brief introduction of synchrotron XRD and Rietveld refinement and their applications in understanding the structural evolution related to the synthetic,thermal runaway,cycling,and high-rate charge/discharge process of LTMO cathode materials.Synchrotron XRD can provide insights into the intermediates and reaction paths in the synthesis process,the origin of thermal runaway,the mechanism of structural decay during cycles,and the structural evolution during high-rate charging/discharging.Future works should focus on the development of higher intensity X-rays to gain more in-depth insights into the intrinsic relationship between their structural characteristics and properties.
文摘The compound CeNi 5Sn was studied by means of X ray powder diffraction technique and refined by Rietveld method. It has a hexagonal structure with space group P 6 3/ mmc (No.194), Z =4, the lattice constants a =0 48912(3) nm, c =1 973(2) nm and D x=8 974 g·cm -3 . The Rietveld structural refinement was performed, leading to R p=0 138 and R wp =0 185. The figure of merit F N for the XRD data is F 30 =82 1(0 0068, 54). The X ray powder diffraction data are presented.
文摘オ-ray powder diffraction data and crystal structure of RE compound NdCoGe3 were studied by using X-ray powder diffraction and refined by the Rietveld profile fitting method. The compound has the tetragonal BaNiSn3type structure, space group I4mm (No.107) a=0.42961(2) nm, c=098147(4) nm, V=0.018114 nm3, Z=2 and Dx=7.717 g·cm-3. The figure of merit FN for the powder data is F30=623 (0.0107, 45). Structure refinement was performed with 110 reflections and led to Rp=11.78% and Rwp=16.56%.
基金China’s Sichuan Science and Technology Program(2019YJ0441)Chengdu Normal University First-class Discipline Construction Major Scientific Research Projects(CS18ZDZ03)+1 种基金Chengdu Normal University Talent introduction scientificresearch special project(YJRC2015-3)The National Natural Science Foundation of China(11647095,51708143,22076034)。
文摘A new ternary Mg_(1.4)Co_(21.6)B_(6) compound in the Mg-Co-B system was synthesized via a conventional solid-state reaction method and the effect of Ni-substitution on its crystal structure,thermal stability,solid solubility and physical properties were systematically investigated.The crystal structure of the Mg_(1.4)Co_(21.6)B_(6) compound was fully determined by the X-ray diffraction technique with Rietveld refinement method.It is found that Mg_(1.4)Co_(21.6)B_(6) crystallizes in the form of C_(6)Cr_(23) structure type(space group:Fm-3m(No.225),a=10.5617(2)A,Z=4).The results showed that the 4a sites have been occupied completely by Co atoms in present compound which with M_(2-x)Ni_(21+x)B_(6) form belonging to the W_(2)Cr_(21)C_(6)-type.When Mg_(1.4)Co_(21.6)B_(6) is repeatedly sintered at elevated temperatures,it becomes unstable and decomposes into Co3B and Mg.The lattice parameters of the Mg_(1.4)Co_(21.6)B_(6) solid solution alters dramtically with increasing Ni substitution,with no regular trend being observed.The electrical and magnetic performances of the 3.6Mg:3Co:17Ni:6B and 3.6Mg:3Co:18Ni:6B(nominal compositions)samples suggest that both samples are typical ferromagnetic materials.The temperature in the maximum drop of theρ(T)curve decreases as a function of the Ni content.Base on the correlation between the critical temperature and Ni content,a linear fitting equation is obtained and the critical temperature of Mg_(1.4)Co_(21.6)B_(6) calculated utilizing the linear fitting equation.The findings in this work may provide certain reference values for material science on electrical magnetic properties and other references for researching the material further.
基金supported by the National Natural Science Foundation of China(21376114)
文摘Ce Y samples with different cerium（Ce） ions initial distribution were prepared by diverse preparation processes. The correlative influence of Ce ions distribution on the intracrystalline structure and catalytic mechanism of Y-type zeolite was studied by X-ray diffraction（XRD）, Rietveld refinement, X-ray fluorescence spectrometry（XRF）, energy-dispersive X-ray spectroscopy（EDS）, infrared（IR） spectra, NH3 temperature-programmed desorption（NH3-TPD）, N2 physical adsorption-desorption and micro-activity test（MAT）. The results indicated that Ce ions were concentrated on the surface（supercage） of Ce Y zeolite would reduce the number of acid sites and the ratio of Br？nsted acid and Lewis acid（B/L）. Once Ce ions concentrated in the sodalite cage, it would participate in the coordination with framework oxygen atoms under the condition of steric hindrance. Meanwhile, Ce ions would preferentially promote the B/L value of weak acid by retaining more intracrystalline framework Al atoms in sodalite cage, which was beneficial to the conversion of heavy oil in FCC process. The optimal initial-distribution of Ce ions could not only save the consumption of rare earth resources but also give the best catalytic performance of Ce Y zeolite catalysts, and these advantages and attributes enabled it to have the potential to be applied in industrial applications.
基金Project(2007CB613607)supported by National Basic Research Program of China
文摘LiNi0.8Co0.1Mn0.1O2 was prepared by a chloride co-precipitation method and characterized by thermogravimetric analysis, X-ray diffractometry with Rietveld refinement,electron scanning microscopy and electrochemical measurements.Effects of lithium ion content and sintering temperature on physical and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 were also investigated. The results show that the sample synthesized at 750℃with 105%lithium content has fine particle sizes around 200 nm and homogenous sizes distribution.The initial discharge capacity for the powder is 184 mA·h/g between 2.7 and 4.3 V at 0.1C and room temperature.
基金Project supported by the Minor Research Project sanctioned by the supported by the Dnyanopasak Shikshan Mandal’s Arts,Commerce and Science College,Jintur,431509,Maharashtra,India (47-766/13)。
文摘The nanocrystalline samarium substituted Co-Zn ferrites with chemical formula Co0.7Zn0.3SmyFe2-yO4(where y=0,0.01,0.02,0.03,0.04) were synthesized by sol-gel autocombustion route.The analysis of Xray diffractograms(XRD) reveals the formation of cubic spinel structure.The planes indexed from XRD analyses were confirmed in the selected area electron diffraction(SAED) image of the sample.Nanocrystalline nature of the particles in the ferrite samples was confirmed by TEM.The morphology was analyzed by scanning electron microscopy(SEM).Magnetic measurements show an increase in the magnetization for x ≤0.03.The decrease in magnetization due to spin canting is observed for x=0.04.The coercivity depends on Sm3+doping concentration,grain size and saturation magnetization.The complex permeability of the ferrites was analyzed as the function of frequency and Sm3+composition(y).The real part of complex permeability varies linearly with the grain size.
基金the CONEX-Plus programme funded by Universidad Carlos III de Madrid(UC3M)the European Commission through the Marie-Sklodowska Curie COFUND Action(Grant Agreement No 801538)+2 种基金supported by the National Research Foundation of Korea Grant funded by the Korean Government(NRF-2019R1l1A3A0106383312)Supporting Project(RSP2021/55),King Saud University,Riyadh,Saudi Arabia,for financial supportfinancial support from Taif University Researchers Supporting Project number(TURSP2020/135),Taif University,Taif,Saudi Arabia。
文摘An eco-friendly,new,and controllable approach for the preparation of manganese oxide(a-MnO_(2))nanorods has been introduced using hydrothermal reaction for supercapacitor application.The in-depth crystal structure analysis ofα-MnO_(2) is analyzed by X-ray Rietveld refinement by using Full Prof program with the help of pseudo-Voigt profile function.The developed a-MnO_(2) electrode attains a remarkable capacitance of 577.7 F/g recorded at a current density value of 1 A/g with an excellent cycle life when is used for 10,000 repeated cycles due to the porous nanorod-morphology assisting the ease penetration of electrolyte ions into the electroactive sites.The diffusive and capacitive contributions of the electrode have been estimated by considering standard numerical packages in Python.After successfully assembling the aqueous symmetric supercapacitor(SSC)cell by utilizing the as-preparedα-MnO_(2),an excellent capacitance of 163.5 F/g and energy density of 58.1 Wh/kg at the constant current density of 0.5 A/g are obtained with an expanded potential frame of 1.6 V.Moreover,the cell has exceptionally withstood up to 10,000 cycles with an ultimate capacitance retention of 94.1%including the ability to light an LED for 18 s.Such findings recommend the developed a-MnO_(2) electrode to be a highly felicitous electrode for the field of energy storage.
基金supported by Consejo Nacional de Ciencia yTecnologia or National Council of Science and Technology(CONACYT,175925)
文摘Doped and undoped TiCh nanoparticles were prepared by Stober method and thermally treated at 600 ℃.The effect of Nd^（3＋） ion on the structure and micro structure of anatase-phase TiCh nanocrystals was studied by Rietveld refinement method using X-ray powder diffraction data.Bond lengths,bond angles,and edges distances were analyzed.The phase formation was confirmed by high-resolution transmission electron microscopy.The adjustment of Ti-0 bond length induced by the addition of Nd^（3＋） ions,reduced the octahedral distortion and altered the octahedral array in the anatase-phase TiCh nanocrystal.The changes of structure and microstructure were mainly observed for TiCh nanoparticles doped with 0.1 at.%of Nd^（3＋） ions and attributed to the cationic substitution of Ti^（4＋） ions which promoted changes in the density of states and gap band of TiCh.The dopant insertion resulted in a better structural stability of the nanocrystals that enhanced their charge transference and photocatalytic efficiency.
基金Project supported by Defence Research and Development Organisation of India(ERIP/ER/0904511/M/01/1252)
文摘The double perovskite oxide barium erbium niobate, Ba2ErNbO6 （BEN） was synthesized by solid state reaction technique. Rietveld refinement of the X-ray diffraction pattern of the sample showed cubic （Fm3m） phase at room temperature. Fourier trans-form infrared spectrum showed two primary phonon modes of the sample at around 387 and 600 cm-1. Raman spectrum of the sam-ple taken at 488 nm excitation wavelength showed four primary strong peaks at 106, 382, 747 and 814 cm-1. Lorentzian lines with 10 bands were used to fit the Raman spectrum. A group theoretical study was performed to assign all the Raman modes. Impedance spectroscopy was applied to investigate the ac electrical conductivity of BEN in a temperature range from 303 to 673 K and in a fre-quency range from 100 Hz-1 MHz. The dielectric relaxation mechanism was discussed in the frame work of permittivity, conduc-tivity, modulus and impedance formalisms. The complex plane plot of the impedance data was modeled by an equivalent circuit con-sisting of two serially connected R-CPE units, （one for the grain and the other for the grain boundary）, each containing a resistor （R） and a constant phase element （CPE）. The R-CPE units were used to incorporate the non-ideal character of the polarization phenome-non instead of an ideal capacitive behaviour. The relaxation time corresponding to dielectric loss was found to obey the Arrhenius law with activation energy of 0.85 eV. The frequency dependent conductivity spectra followed the Jonscher power law. The Cole-Cole model was used to investigate the dielectric relaxation mechanism in the sample.
文摘Two compounds, Dy_2(WO_4)_3 and GdY(WO_4)_3, were synthesized by using thestandard solid state reaction technique. The crystal structure was determined by powder X-raydiffraction and Rietveld refinement method. It is found that both compounds have Eu_2(WO_4)_3-typemonoclinic structure, with space group C 2/c, Z = 4. The unit cell parameters of Dy_2(WO_4)_3 are a= 0.75981(1) nm, b = 1.13220(1) nm, c = 1.13254(1) nm, and beta = 109.8001(3) deg, and those ofGdY(WO_4)_3 arc a = 0.76175(1) nm, b = 1.13543(1) nm, c = 1.13496(2) nm, and beta = 109.8015(13)deg. Each W atom has four oxygen nearest neighbors, while each rare-earth atom is surrounded byeight oxygen atoms. WO_4 tetrahedra share their four vertices with REO_8 (RE = Dy, Gd, or Y)trigondodecahedra and some REO_8 trigondodecahedra share an edge with each other. The phasetransition and the magnetic properties were investigated by differential thermal analysis (DTA) anddc superconducting quantum interference device (SQUID) magnetometer.
文摘Upconversion （UC） phosphor Tm3＋ doped YF3 nano-erystals were prepared by hydrothermal method under different conditions and characterized by Field Transmission electron microscopy （TEM）, Scanning electron microscopy （SEM） and X-ray diffraction （XRD）. Their UC luminescence properties were studied by fluorescence spectrophotometer with 980 nm diode laser excitation, and impact of different grain sizes and morphology on the UC luminescence intensity was discussed. The fluorescence decay lifetime was calculated by Multi-exponential function fitting method. Results show that UC emission intensity was enhanced with the reduction of grain size, and the decay lifetime is 0.60 us.
基金financially supported by the Defence Research and Development Organisation(DRDO),the Government of India(No.ERIP/ER/0903830/M/01/1235)
文摘Specimens of Pb1-1.5xLax（Zr0.53 Ti0.47）1-y-zFeyNb2O3 （x = 0, 0.004, 0.008, 0.012, and 0.016, y = z = 0.01） （PZTFN） ceramics were synthesized by a semi-wet route. In the present study, the effect of La doping was investigated on the structural, microstructural, dielectric, piezoelectric, and ferroelectric properties of the ceramics. The results show that, the tetragonal （space group P4mm） and rhombohedral （space group R3c） phases are observed to coexist in the sample at x = 0.012. Microstructural investigations of all the samples reveal that La doping inhibits grain growth. Doping of La into PZTFN improves the dielectric, ferroelectric, and piezoelectric properties of the ceramics. The hys- teresis loops of all specimens exhibit nonlinear behavior. The dielectric, piezoelectric and ferroelectric properties show a maximum response atx 〉 0.012, which corresponds to the morphotropic phase boundary （MPB）.
