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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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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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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
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Elucidating the structure and optimising the photoluminescence properties of Sr2Al3O6F: Eu3+ oxyfluorides for cool white-LEDs
摘要： Herein, Sr2Al3O6F in hexagonal symmetry was synthesized via a solid-state methodology. The X-ray diffraction pattern of Sr2Al3O6F was refined by the Rietveld refinement with lattice parameters a = 17.8232(1) ? and c = 7.2168(0) ?. The stability of the crystal structure is further confirmed from the results of bond valence sums and the global instability index. The theoretical calculations of the electronic and optical behaviors of the Sr2Al3O6F were analyzed by density functional theory and the obtained results of the lattice parameters and direct bandgap were found close to the experimental data. The chemical states and elemental composition of Sr2Al3O6F were also authenticated by X-ray photoelectron spectroscopy (XPS). To evaluate the suitability of the Sr2Al3O6F structure as high efficient red phosphor, a series of Eu3+ doped Sr2-xEuxAl3O6F (x = 0.0 to 0.10) were synthesized, which showed intense red-orange emission (5D0→7F1,2) at UV and blue excitations. The photoluminescence intensity corresponding to 5D0→7F2 transition decreased significantly for x = 0.10 due to the luminescence quenching. Nevertheless, further enhancement in photoluminescence of Sr1.9Al3O6F: Eu0.1 sample was realized with the substitution of 0.1 mol Ba2+ ion for 0.1 mol Sr2+ ion. The various radiative properties of the emission bands were also analyzed through the Judd-Ofelt theory. The optimized Sr1.8Al3O6F: Ba0.1/Eu0.1 phosphor showed high red color purity (> 95%), and moderate thermal stability of around 72% at 150 oC, suggesting that it could be an ideal red component for white-LEDs. A white-LED comprising the commercial yellow phosphor and the optimized sample showed bright white light having the CRI of 80.5%, CCT of 5510 K, and CIE of (0.33, 0.36) indicating that Sr1.8Al3O6F: Ba0.1/Eu0.1 phosphor is an appropriate red component for cool white-LEDs.
关键词： Eu3+-doping,Rietveld refinement,Hexagonal Sr2Al3O6F,density functional theory,white-LEDs,red phosphors
更新于2025-09-19 17:13:59
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Investigation of structural, optical and electrical properties of Sr2SnO4, Sr1.99Eu0.01SnO4 and Sr2Sn0.99Eu0.01O4 Ruddlesden Popper oxide
摘要： Structural, electrical and optical properties of samples have been reported in this paper. The samples with compositions Sr2SnO4, Sr1.99Eu0.01SnO4 and Sr2Sn0.99Eu0.01O4 are prepared by solid state ceramic route followed by calcination at temperature 1000oC for 8 h. Rietveld refinement of powder X-ray diffraction (XRD) data showed tetragonal structure in all samples with space group (I4/mmm). X-ray photoelectron spectroscopy (XPS) studies indicate the presence of Sn in Sn4+ and Sn2+ state in both the samples. The electrical conductivity of the sample follows universal johnscher’s law.“ ?? = ?????? + ?????? ”. Temperature dependent electrical conductivity in samples Sr2SnO4, Sr1.99Eu0.01SnO4 and Sr2Sn0.99Eu0.01O4 with activation energy 0.16, 0.17, 0.16 eV respectively. Conduction in these samples show intense emission peak at 577, 595 and 612 nm assigned to transitions from 5D0?7FJ (J=0, 1, 2, 3) levels of Eu3+. Higher the value of conductivity ??????and integrated area of emission peak for Sr1.99Eu0.01SnO4 is making it more multifunctional than Sr2Sn0.99Eu0.01O4.
关键词： Ghosh scaling,Ruddlesden Popper oxide: Sr2SnO4,Rietveld refinement,Universal Johnscher’s power law
更新于2025-09-11 14:15:04
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Structure-directing lone pairs: Synthesis and Structural Characterization of SnTiO3
摘要： SnTiO3 was successfully synthesized for the first time in bulk form by soft chemistry. STEM and Rietveld refinement show that SnTiO3 adopts a structure similar to the archetypical ilmenite-type structure, forming a honeycomb lattice of edge-sharing TiO6-octahedra, which are decorated with Sn2+. Due to formation of a van der Waals gap between the individual layers and hence close energetic minima of different stacking types, SnTiO3 forms multiple stacking orders and twinning domains that we describe by systematic DIFFaX-simulations. The structure is governed by the tin lone pairs, which influence the stacking of the layers as well as local distortions observed by EELS and NMR potentially leading to a wide range of applications.
关键词： DFT,van der Waals gap,Rietveld refinement,soft chemistry,STEM,ilmenite-type structure,EELS,SnTiO3,NMR
更新于2025-09-09 09:28:46
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Structural, Infrared, Magnetic, and Electrical Properties of Ni0.6Cd0.2Cu0.2Fe2O4 Ferrites Synthesized Using Sol-Gel Method Under Different Sintering Temperatures
摘要： Ni0.6Cd0.2Cu0.2Fe2O4 ferrites were synthesized using sol-gel method under different sintering temperatures. XRD patterns with the Rietveld refinement indicate that samples crystallize in the cubic spinel structure. The increase of sintering temperature leads successively to the increase of lattice constant, average crystallite size, intensities of absorption bands, magnetization, and electrical conductivity of the prepared ferrites. Dielectric constants decrease with frequency and their behaviors have been investigated using the interfacial polarization theory predicted by Maxwell. The modulus analysis shows the presence of electrical relaxation phenomenon and non-Debye nature for the samples. An appropriate electrical equivalent circuit was used to analyze the Nyquist plots, and the results show that the conduction mechanism of the synthesized ferrites is mainly due to the grain boundary contribution.
关键词： Ferrites,conductivity,Rietveld refinement,Sol-gel method,Infrared properties,Dielectric properties
更新于2025-09-09 09:28:46