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Structural, Optical, and Dielectric Studies on Sr-Doped Biferroic YCrO3
摘要： In this work, the solid-state synthesis of Y1-xSrxCrO3 (x = 0.0, 0.1) samples has been reported. The X-ray diffraction data analysis confirmed that the synthesized samples have crystallized into the orthorhombic phase with the assigned space group Pbnm. The Rietveld refinement of the XRD data confirmed the structure and other related parameters. The slight variation in the lattice parameters and negligible shift in the reflection peaks reveals the uniform dispersion of Sr at Y-site in the parent YCrO3 matrix. The dielectric characterization revealed the good dielectric nature of the prepared samples which decreases with Sr doping. Field emission scanning electron microscopy (FE-SEM) revealed that an agglomeration type process has taken place in the sample preparation. Fourier transform infrared (FTIR) characterization witnessed the formation of orthorhombic phase of the samples under study displaying sharp absorption bands corresponding to Cr–O stretching, Y/Sr–O stretching, and O–Cr–O deformation vibration, respectively. UV-Vis spectroscopy analysis revealed the dual direct allowed bandgap of the samples assigned to the Cr3+ ion transition in the ground level.
关键词： Nanoparticles,Structure,Rietveld refinement,Morphology,Dielectric properties
更新于2025-09-23 15:23:52
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Study on Charge transportation and scaling behavior of CsPbI3 microwires
摘要： Cesium lead iodide (CsPbI3) has been prepared by a new experimental hazard free precipitation technique. X-ray diffraction spectra have been interpreted with Rietveld refinement which assures the orthorhombic phase of CsPbI3. Energy dispersive X-ray fluorescence spectra confirms the formation of ternary compound. Orthorhombic to cubic phase transition has been studied by observing hysteresis loop in R(T)-T plot for forward-reverse temperature scan. The intra-grain and inter-grain contribution of CsPbI3 to dielectric relaxation has been accounted by fitting the complex impedance plot (Cole-Cole plot). The value of FWHM in Z″(ω)-lnf or M″(ω)-lnf plot is greater than 1.141 decades which reveals the non-Debye type relaxation within material. The broad relaxation peak signifies that there is a distribution of relaxation time over a mean value. Moreover, Z″ & M″ have been plotted in scaled coordinate to check whether the distribution of relaxation time is temperature dependent or not. The frequency dependent relative permittivity represents the decreases of polarizations with frequency which have been successfully analyzed by Koop’s theory. Here, activation energies are equal for different formalism, suggests that the same type charge carriers involved in conduction as well as relaxation process. Ac conductivity has been interpreted by using Jonncher’s power law and frequency exponent (n) increases with temperature which suggests the presence small polaron hopping mechanism.
关键词： Joncher’s power law,dielectric relaxation,Rietveld,Hysteresis,Cole-Cole plot,CsPbI3 micro-wire
更新于2025-09-23 15:23:52
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Magnetic metamorphosis of structurally enriched sol-gel derived SnO2 nanoparticles
摘要： Pure SnO2 and aliovalent substituted polycrystalline Sn0.98?xLa0.02ZnxO2 (x = 0.02, 0.04 and 0.06) samples have been synthesized via sol-gel technique. Rietveld re?nement of X-ray di?raction (XRD) patterns con?rm the single phase tetragonal rutile-type (P mnm 42/) crystalline structure for all the synthesized samples. Crystallite size from XRD analysis is found to decrease from 14 nm to 11 nm as x increases from 0 to 0.06 in Sn0.98?xLa0.02ZnxO2 matrix. Transmission Electron Microscopy further reveals the decrease in average crystallite size from 7 nm for pure SnO2 to 5 nm with increase in Zn2+ concentration in system. Morphological study through Field Emission Scanning Electron Microscopy reveals the agglomeration of nanoparticles on increasing the Zn concentration. The room temperature photoluminescence (PL) measurements mark the change in peak intensity centered around 300–450 nm upon La and Zn co-doping into SnO2 lattice. Deconvolution of PL peak unveil the presence of defects/vacancies and local disorders in (La, Zn) co-doped SnO2 matrix. Further, the magnetic properties have been studied using Vibrating Sample Magnetometer, which envisage the room temperature ferromagnetism (RTFM) in nonmagnetic La3+ and Zn2+ ion modi?ed SnO2. The observed RTFM in (La, Zn) co-doped SnO2 is mainly due to oxygen vacancies which is also supported by PL results.
关键词： Rietveld re?nement,RTFM,SnO2 nanoparticles,Defect states
更新于2025-09-23 15:23:52
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Exploration of structural, vibrational and spectroscopic properties of self-activated orthorhombic double molybdate RbEu(MoO4)2 with isolated MoO4 units
摘要： RbEu(MoO4)2 is synthesized by the two-step solid state reaction method. The crystal structure of RbEu(MoO4)2 is defined by Rietveld analysis in space group Pbcn with cell parameters a=5.13502(5), b=18.8581(2) and c=8.12849(7) ?, V=787.13(1) ?3, Z=4 (RB=0.86%). This molybdate possesses its phase transition at 817 K and melts at 1250K. The Raman spectra were measured with the excitation at l =1064 and 514.5nm. The photoluminescence spectrum is evaluated under the excitation at 514.5nm. The absolute domination of hypersensitive 5D0(cid:1)7F2 transition is observed. The ultranarrow 5D0(cid:1)7F0 transition in RbEu(MoO4)2 is positioned at 580.2nm being 0.2nm blue shifted, with respect to that in Eu2(MoO4)3.
关键词： Rietveld refinement,rubidium europium molybdate,Raman luminescence,solid state reaction,DSC
更新于2025-09-23 15:23:52
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Changes of optical transition models caused by crystal structural changes in CaSe2O5
摘要： The present work concerns calcium pyroselenites CaSe2O5 with two independent crystal structures, their di?erence physical properties and phase transformations. α-CaSe2O5 in orthorhombic form shows 2D calcium oxide anionic layers whereas new compound β-CaSe2O5 crystallizes in monoclinic space group C2/c. It's a new structure type with 1D calcium oxide thick chains which are further connected by Se2O5 dimers. Rietveld re?nement indicates that the weight fraction for α/β-CaSe2O5 mixture phase was found to be 84.5% and 15.5% for α- and β-CaSe2O5, respectively. Optical di?use re?ectance spectrum coupled with Kubelka–Munk ?t gives a result that α-CaSe2O5 adopts direct optical transition model while β-CaSe2O5 is an indirect semiconductor. The experimental result matches well with the prediction of theory calculation. The optical bandgap values were ?tted to be 4.74 and 4.12 eV for α- and β-CaSe2O5, respectively. Thermal analysis coupled with variable temperature powder XRD indicates the phase transformation between these two phases.
关键词： Selenite,Optical bandgap,Rietveld re?nement,Phase transformation
更新于2025-09-23 15:23:52
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Photoactive and Non-Hazardous Kaolinite/ZnO Nanocomposite: Characterization and Reproducibility of the Preparation Process
摘要： Photoactive and non-hazardous kaolinite/ZnO nanocomposite with 50 wt.% of ZnO nanoparticles was prepared using simple and cheap hydrothermal method. The resulting solid phase was separated by decantation, and dried at 105 °C. Calcination of the nanocomposites at 600 °C led to the kaolinite—metakaolinite phase transformation, to further growth of ZnO crystallites, and to significant increase in photodegradation activity. Whereas, for the several applications, e.g., in brake industry, the larger amount of composites is needed, thus, the evaluation of the reproducibility of preparation process is one of the crucial parameter. Prepared nanocomposites were deeply characterized by using X-ray fluorescence spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and Rietveld quantitative phase analysis. Photodegradation activity was evaluated by the discoloration of Acid Orange 7 aqueous solution under UV irradiation. All used analytical techniques and methods confirm the reproducibility of the preparation process and as well that ZnO nanoparticles are anchored tightly on the clay surface which prevents the release to the environment.
关键词： Nanocomposite,Rietveld,Kaolinite,Photoactivity,Zinc Oxide
更新于2025-09-23 15:22:29
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Effect of Ni substitution on the structural and optical properties of SrZr1-xNixO3 (0.05≤x≤0.20) perovskites
摘要： Ni2+ substituted SrZr1-xNixO3 (x = 0.05, 0.10, 0.15, 0.20) perovskites are synthesized by the solid-state reaction method. Their structural, morphological and optical properties are characterized using X-ray diffraction (XRD), scanning electron microscopy with attached energy dispersive spectroscopy (SEM-EDS), UV-Visible (UV-Vis) and photoluminescence spectroscopy (PL). The XRD patterns of all the samples show the formation of a single phase, i.e. orthorhombic phase, which is further confirmed by Rietveld refinement. Structural ordering increases with an increase in the concentration of Ni2+ substitution with an increase in the mean crystallite size. The optical band gap of all the samples is in the insulating range, i.e., around 5 eV. The intensity of the PL spectra decreases with substitution concentration due to the quenching effect.
关键词： Rietveld refinement,Photoluminescence,Band gap,Perovskite structure
更新于2025-09-23 15:22:29
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Electrical response in poled (Bi <sub/>0.5</sub> Na <sub/>0.5</sub> ) <sub/>0.935</sub> Ba <sub/>0.065</sub> TiO <sub/>3</sub> ceramics
摘要： A ferroelectric material (Bi0.5Na0.5)0.935Ba0.065TiO3 (BNBT) with a perovskite structure was poled and characterized by electrical impedance spectroscopy as a function of temperature, X-ray diffraction, and Rietveld refinement. The ac conductivity showed a low-frequency dispersion, supporting the idea of heterogeneous potential wells favored by Bi3+, Na+, and Ba2+ on the A site of the perovskite type of structure. The activation energies for ac conduction depend on the studied frequency. The permittivity and electrical modulus showed a distribution of the relaxation time associated with the delay in the orientation of the dipoles and an important contribution to the short-range conductivity.
关键词： electrical behavior,Rietveld refinement,Phase change,dielectric permittivity,BNBT
更新于2025-09-23 15:21:01
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Structure stability, bond characteristics and microwave dielectric properties of co-substituted NdNbO4 ceramics
摘要： Structure-property relationship of co-substituted (Mg2+1/4Mo6+3/4)5+, (Al3+1/3Mo6+2/3)5+, (Si4+1/2Mo6+1/2)5+, (Zr4+1/2Mo6+1/2)5+ for Nb5+ in NdNbO4 ceramics was investigated systematically. The remarkable differences in dielectric properties of each composition originated from their bond characteristics and structure stability. The elongated/compressed bonds have an effect on the cell volume and polarization. And the average bond covalency of Nb-O bond was responsible for the development of permittivity. Q×f values and the total lattice energy went up to maximum when (Si0.5Mo0.5) occupied Nb-site. Variations of lattice energy together with Nb-O bond energy suggest that a more stable structure was obtained through co-substitution. The optimal microwave dielectric properties is: εr=18.97, Q×f=49466GHz, τf=7.34 ppm/℃ for NdNb0.97(Si0.5Mo0.5)0.03O4, sintered at 1250℃.
关键词： bond characteristics,Rietveld refinement,NdNbO4,microwave dielectric properties
更新于2025-09-23 15:21:01
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Simultaneous two-phase formation model in synthesized SBN/NFO using the in-situ modified Pechini method
摘要： The main aim of this research was to investigate the in situ co-synthesis of Sr0.61Ba0.39Nb2O6/NiFe2O4 (SBN/NFO) magnetoelectric particulate composites using a modified Pechini method, as well as propose a model to understand the simultaneous formation of two crystalline phases in these materials. Powder samples of SBN/NFO with 50/50, 70/30 and 80/20 molar ratios were analyzed using structural analysis techniques, combining both X-ray diffraction and Rietveld structural refinement in order to identify and quantify the phases in the samples. Based on the results, a phase formation model for the co-synthesis was proposed considering Hume-Rothery rules. This model led us to conclude that the formation of precipitates during the development of the polymeric resin by the modified Pechini method would be the main factor responsible for the presence of spurious phases in the synthesis of SBN/NFO composites. The reduction in the concentration of spurious phases may occur during the polymer resin formation step or when using a different solvent to prevent the formation of precipitates.
关键词： SBN/NFO,Rietveld refinement,modified Pechini method,in situ co-synthesis,formation model phases
更新于2025-09-19 17:15:36