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magnetic, Dielectric and Complex Impedance Properties of xBa_(0.95)Sr_(0.05)TiO_3–(1-x)BiFe_(0.9)Gd_(0.1)O_3multiferroic Ceramics

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Acta metallurgica Sinica(English Letters) 2016年第6期29卷 505-517页

作者： m.J.miah a.k.m.akther hossain Department of Physics Bangladesh University of Engineering and Technology Department of Physics Comilla University

xBa_（0.95）Sr_（0.05）TiO_3–（1-x）BiFe_（0.9）Gd_（0.1）O_3[x BST–（1-x）BFGO]（x = 0.00, 0.10, 0.20 and 0.25） multiferroic ceramics were prepared by the standard solid-state reaction technique. Structural characterization was performed by X-ray diffraction. All the samples showed rhombohedral distorted perovskite structure. Surface morphology of the ceramics was studied by the field emission scanning electron microscope（FESEm）. From the FESEm observation, the grain size was observed to be decreased with increasing BST content. Enhanced magnetic properties were observed in BFGO with the increase in BST content because of large lattice distortion. The complex initial permeability increased with the increasing of BST content. The study of dielectric properties showed that the dielectric constant increased, whereas dielectric loss decreased with increasing of BST content due to the reduction of oxygen vacancies. An analysis of the electric impedance and modulus with frequency was performed at different temperatures. Non-Debye-type relaxation processes occur in the compound which was confirmed from the nature of the Cole–Cole plot. The DC conductivity was found to increase with the rise in temperature which indicates the semiconducting behavior of the compound with characteristics of the negative temperature coefficient of resistance. The activation energy, responsible for the relaxation determined from the modulus spectra（0.246 eV）, was found to be almost same as the value obtained from the impedance study（0.240 eV）, indicating that charge carriers overcome the same energy barrier during relaxation. The frequency response of imaginary parts of electric impedance and modulus suggested that the relaxation in xB ST–（1-x）BFGO ceramics follows the same mechanism at various temperatures.

关键词： magnetic properties Dielectric properties Impedance spectroscopy Activation energy

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Structural,Dielectric and Complex Impedance Spectroscopy Studies of Lead Free Ca_(0.5+x)Nd_(0.5-x)(Ti_(0.5)Fe_(0.5))O_3

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Journal of materials Science & Technology 2013年第4期29卷 323-329页

作者： m.R.Shah a.k.m.akther hossain Department of Physics University of PrimeasiaBananiDhaka 1213Bangladesh Department of Physics Bangladesh University of Engineering and TechnologyDhaka 1000Bangladesh

Structural and various electrical properties of polycrystalline Ca0.5＋xNd0,5-x（Ti0.5Fe0.5）O3, prepared by standard solid state reaction technique, were studied. Formation of single phase orthorhombic structure of the compositions was confirmed by X-ray diffraction study. The composition dependence of lattice parameters, density and microstructural study show that they vary significantly with Ca content. The dielectric measurements were carried out at room temperature as function of frequency and composition. The experimental results reveal that the dielectric constant （ε′） increases with increasing Ca content. Similar behavior is observed for the dielectric loss （tanδ） and ac conductivity （σac）. In complex impedance analysis it is observed that the real part （Z′） vs imaginary part （Z″） graph exhibits a tendency of formation of a single semicircular arc for each composition of samples. Different parameters were determined by fitting the experimental data in Cole-Cole empirical formula. A dominance of grain boundary resistance （Rgb） is observed. The Rgb decreases with increasing Ca content. The high ε′ observed in present samples are suitable for fabrication of devices.

关键词： Crystal structure Dielectric properties Lead free Perovskite Solid state reaction

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Influence of Lanthanum on the microstructural and Dielectric Properties of Polycrystalline Ba(Ti0.5Fe0.5)O3

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Chinese Physics Letters 2012年第4期29卷 213-216页

作者： m.R.Shah a.k.m.akther hossain Department of Physics Primeasia UniversityBananiDhaka-1213Bangladesh Department of Physics Bangladesh University of Engineering and TechnologyDhaka-1000Bangladesh

Various polycrystalline Ba1-x Lax (Ti0.5 Fe0.5 )O3 are prepared by using the standard solid state reaction *** shaped samples prepared from each composition are sintered at 1200℃ for 5 h.X-ray diffraction patterns of these compositions confirm the formation of a single phase perovskite *** lattice parameters are decreased but the average grain size increases with the increase of La *** dielectric constant,dielectric loss and ac conductivity are studied as a function of frequency for various compositions,and their behaviors are explained on the basis of the maxwell-Wagner model A three-times enhancement of the dielectric constant is observed with the increase of La content.

关键词： Ti structure technique

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Complex impedance and electric modulus studies of magnetic ceramic Ni_(0.27)Cu_(0.10)Zn_(0.63)Fe_(2)O_(4)

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Journal of Advanced Ceramics 2015年第3期4卷 217-225页

作者： m.BELAL HOSSEN a.k.m.akther hossain Department of Physics Chittagong University of Engineering and TechnologyChittagongBangladesh Department of Physics Bangladesh University of Engineering and TechnologyDhakaBangladesh

The electrical properties of Ni_(0.27)Cu_(0.10)Zn_(0.63)Fe_(2)O_(4)(NCZF)prepared from auto combustion synthesis of ferrite powders have been studied by impedance and modulus *** studied frequency and temperature dependencies of impedance and electric modulus of NCZF in a wide frequency range(20 Hz-5 mHz)at different measuring temperatures T_(Sm)(30-225℃).The complex impedance spectra clearly showed both grain and grain boundary effects on the electrical *** observed impedance spectra indicated that the magnitude of grain boundary resistance R_(gb) becomes more prominent compared to grain resistance R_(b) at room temperature,and with the increase in T_(Sm),R_(gb) decreases faster than the intrinsic R_(b).The frequency response of the imaginary part of impedance showed relaxation behavior at every T_(Sm),and the relaxation frequency variation with T_(Sm) appeared to be of Arrhenius nature and the activation energy has been estimated to be 0.37 eV.A complex modulus spectrum was used to understand the mechanism of the electrical transport process,which indicated that a non-Debye type of conductivity relaxation characterizes this material.

关键词： ferrimagnetic ceramics impedance spectroscopy electric modulus temperature dependence

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High permittivity and low dielectric loss analysis of lead free Sr_(1-x)La_x(Ti_(0.5) Fe_(0.5))O_3

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Journal of Central South University 2013年第12期20卷 3363-3371页

作者： m.R.Shah a.k.m.akther hossain Department of Physics Primeasia University Department of Physics Bangladesh University of Engineering and Technology

The structural and electrical properties of lead free Srx-xLax（***.5）O3 （SLTFO） prepared by standard solid state reaction technique were studied. The X-ray diffraction analysis confirmed the formation of a single-phase cubic perovskite structure. The compositional dependence of lattice constant, density and microstructural studies show that they vary significantly with La3＋ content. When measured at 10 kHz, all the compositions of SLTFO at room temperature exhibit a high permittivity （about 104） and low dielectric loss （about 10-3）. SLTFO also display minimum dielectric loss within the lower and higher limits of frequency, indicating that the samples are of good quality. It is concluded from the calculated ac conductivity that the conduction is due to mixed polarons hopping. The complex impedance plot exhibits a tendency of forming a single semicircular arc for all compositions, which implies a dominance of grain boundary resistance on the impedance. Impedance parameters were determined by fitting the experimental data with Cole-Cole empirical formula. The results of the present experiment indicate that the lead free SLTFO materials with higher permittivity and lower dielectric loss have possible practical applications.

关键词： dielectric properties solid state reaction Sr titanate X-ray diffraction

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Correlations of Structural, Dielectric, magnetic and magnetoelectric Properties of Ca1-xSrx(Fe0.5Ta0.5)O3multiferroic Ceramics

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materials Sciences and Applications 2017年第1期8卷 64-84页

作者： m.k.H.Bhuiyan m.A.Gafur m.N.I.khan A.A.momin a.k.m.akther hossain Department of Physics Bangladesh University of Engineering&TechnologyDhakaBangladesh Pilot Plant&Process Development Centre DhakaBangladesh materials Science Division Atomic Energy CentreDhakaBangladesh

Conventional solid state reaction technique was used to synthesize Ca1-xSrx(Fe0.5Ta0.5)O3 multiferroic ceramics (where x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5). Powder of ingredients was mixed thoroughly in stoichiometric amount and calcined at 1150°C for 5 h. Disk and toroid shaped samples prepared from each composition were sintered at 1450°C for 5 h. The XRD analysis confirms that all compositions are single phase cubic perovskite structure. The theoretical and bulk density increases with increase of Sr content, which may be attributed to the fact that the atomic weight and density of Sr are larger than those of Ca. The average grain size increased with increasing Sr content up to x = 0.2, and then decreased with further increase of Sr content. Frequency dependent dielectric constant shows usual dielectric dispersion at lower frequencies due to maxwell-Wagner type interfacial polarization. The higher values of real and imaginary part of impedance at lower frequencies are also due to the fact that all kinds of polarization mechanism are present and increase with Sr content indicating the enhancement property of the composition. The continuous dispersion on increasing frequency contributes to the conduction phenomena. Two semicircles correspond to the grain boundary and grain resistance separately. The complex modulus analysis reveals the polaron hopping and negligibly small contribution of electrode effect. The continuous dispersion on increasing frequency may be contributed to the conduction phenomena. The ac conductivity, σac, was derived from the dielectric measurement and it increases with increase of frequency for all the compositions and can also be explained on the basis of polaron hopping mechanism. At higher frequencies conductive grains are more active, and thereby increases of hopping of charge carrier contribute to rise in conductivity. The real part of initial permeability increased with increasing Sr content up to x = 0.2, and then decreased further incr

关键词： Perovskite Impedance Spectroscopy Initial Permeability Saturation magnetization magnetoelectric Voltage Coefficient

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Synthesis and magnetic Properties of Ba2Ni2–xZnxFe12O22

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World Journal of Condensed matter Physics 2012年第4期2卷 181-187页

作者： Sajal Chandra mazumdar A. k. m. akther hossain Department of Physics Bangladesh University of Engineering and Technology Dhaka Bangladesh Department of Physics Comilla University Comilla Bangladesh

Y-type hexagonal ferrites with the nominal chemical composition Ba2Ni2-xZnxFe12O22 (0.0 ≤ x ≤ 0.6 with a step of 0.1) have been synthesized by the conventional solid state reaction method and sintered in the temperature range 1150℃-1250℃ to study their structural and magnetic properties. The aim of the present work is to increase the magnetic properties of Y-type hexaferrites by Zn substitution. X-ray diffraction analysis confirms the formation of the hexagonal phase. The effect of chemical composition on the lattice parameter, density and porosity is studied. The lattice parameter increases with Zn substitution. The density increases with Zn substitution up to a certain level and after that density decreases. The ac magnetic properties of the hexaferrites sintered at temperature 1200℃ are characterized within the frequency range 100 kHz -120 mHz. The real part (μi') of the complex initial permeability for different compositions indicates that μi' decreases with increase in frequency. The permeability increases with the increase in Zn content, reaches a maximum value and then decreases with further increase in Zn content. magnetization has been measured using the Superconducting Quantum Interference Device (SQUID) magnetometer. The saturation magnetization is observed to be maximum at x = 0.1 and then decreases with Zn content for x > 0.1. From the m-H curve it is clear that at room temperature the polycrystalline Ba2Ni2-xZnxFe12O22 compositions are in ferrimagnetic state.

关键词： Hexagonal Ferrites X-ray Diffraction Porosity Permeability magnetization

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Sintering Temperature Dependent magnetic and Dielectric Properties of Polycrystalline xBa0.95Sr0.05TiO3-(1 - x)BiFe0.90Gd0.10O3Ceramics

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Journal of Applied mathematics and Physics 2020年第9期8卷 1799-1813页

作者： m. J. miah mehbuba Rashid mouri A. Ahad m. A. Taher A. k. m. akther hossain Department of Physics Comilla University Cumilla Bangladesh Department of Physics Bangladesh University of Engineering & Technology Dhaka Bangladesh

Polycrystalline xBa0.95Sr0.05TiO3-(1 - x)BiFe0.90Gd0.10O3 ceramics were prepared by standard solid state reaction technique using the solid solution of BaCO3, SrCO3, TiO2, Bi2O3, Fe2O3 and Gd2O3. The compound is a BiFeO3 based multiferroic material which contains both magnetic and electric properties. The synthesized ceramics noticed better properties than xBaTiO3-(1 - x)BiFeO3 because of adding rare earth element Gd which have higher magnetic moment than Fe. The prepared samples were sintered at 900˚C, 950˚C and 1000˚C for 1 h. The effect of sintering temperature on density of the compound, complex initial permeability, dielectric properties and complex impedance analysis was reported in this article. Density of the ceramics was found to be enhanced with the rise in sintering temperature which implied porosity of the compound decreased when sintering temperature was increased. Enhanced complex initial permeability was noticed for the samples up to 950˚C and this might be attributed to reducing the motion of domain wall when the ceramics were sintered above 950˚C. Value of dielectric constant increased whereas dielectric loss decreased and these modifications might be expected because of changing d

关键词： Ceramics Sintering Temperature Complex Initial Permeability Dielectric Properties

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Fractionation of Organic Carbon and Stock measurement in the Sundarbans mangrove Soils of Bangladesh

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American Journal of Climate Change 2021年第4期10卷 561-580页

作者： Sayada momotaz akther md mahfuz Islam md Faruque hossain Zakia Parveen Department of Soil Water and Environment University of Dhaka Dhaka Bangladesh Department of Crop and Soil Sciences North Carolina State University Raleigh NC 27695 USA OSCm FBA American International University-Bangladesh Kuril Dhaka Bangladesh

mangrove soils are well known for their high capacity of storing organic carbon (SOC) in various pools;however, a relatively small change in SOC pools could cause significant impacts on greenhouse gas concentrations. Thus, for an in-depth understanding of SOC distribution and stock to predict the role of Sundarbans mangrove in mitigating global warming and greenhouse effects, different extraction methods were employed to fractionate the SOC of Sundarbans soils into cold-water (CWSC) and hot-water (HWSC) soluble, moderately labile (mLF), microbial biomass carbon (mBC), and resistant fractions (RF) using a newly developed modified-method. A significant variation in total SOC (p k (p k density (p mangrove forest were observed. In most soils, bulk density increased from the surface to 100 cm depth. The total SOC concentrations were higher in most surface soils and ranged from 1.21% ± 0.02% to 8.19% ± 0.09%. However, C in lower layers may be more resistant than that of upper soils because of differences in compositions, sources and environmental conditions. SOC was predominately associated with the resistant fraction (81% - 97%), followed by mLF (2% - 10%), HWSC (1% - 4%), mBC (~0% - 4%), and CWSC (~0% - 3%). The significant positive correlations between different C fractions suggested that C pools are interdependent and need proper management plans to increase these pools in Sundarbans soils. The SOC stock of the studied areas ranged between 16.75 ± 3.83 to 135.12 ± 28.61 kg·C·m−2 in 1 m soil profile and has an average of 31.80 kg·C·m−2. The substratum soils had more carbon than the upper layers in the Sundarbans wetland due to burial and preservation of carbon by frequent tidal inundation. A higher SOC stock in

关键词： Carbon Sequestration Carbon Sink Carbon Source Soil Organic Carbon Stock Sundarbans mangrove Forest

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Structural and magnetic Properties of mn0.50-xZn0.50CuxFe2O4

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materials Sciences and Applications 2013年第12期4卷 831-838页

作者： Farhad Alam mohammad H. R. khan Hari N. Das akther A. k. m. hossain Department of Arts and Sciences Ahsanullah University of Science and Technology Dhaka Bangladesh Department of Physical Sciences School of Engineering and Computer Science Independent University-Bangladesh Dhaka Bangladesh Department of Physics Bangladesh University of Engineering and Technology Dhaka Bangladesh materials Science Division Atomic Energy Centre BAEC Dhaka Bangladesh

mn0.50-xZn0.50CuxFe2O4 (where x = 0.0 - 0.3) ferrites have been synthesized by auto combustion method. X-ray diffraction patterns reveal that all compositions are of single phase cubic spinel structure. The lattice parameter decreases with the increase in Cu2+ content obeying the Vegard’s law. The bulk density, average grain size, initial permeability, Néel temperature and saturation magnetic induction of mn0.50-xZn0.50CuxFe2O4 increased with increasing Cu2+content. It is observed that both density and initial permeability increase with increasing sintering temperature. The maximum initial permeability is found to be 1061 which is almost four times greater than that of the parent composition. The resonance frequency of all the samples shifts towards the lower frequency as the permeability increases with Cu2+ content. It is observed from B-H loops of mn0.50-xZn0.50CuxFe2O4 that coercivity decreases and retentivity increases with Cu2+ content. Possible explanations for the observed magnetic properties with various Cu2+ contents are discussed.

关键词： Combustion method mn-Cu-Zn Ferrites Initial Permeability B-H Loop

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