0.5BiDyxFe1-xO3-0.5PbTiOa（0.5BDxF1-x-0.5PT） （x=0.00, 0.05, 0.10, 0.15, 0.20） multiferroic composites were pre- pared by conventional solid state reaction method. Structural characterization was performed by X-ray ...0.5BiDyxFe1-xO3-0.5PbTiOa（0.5BDxF1-x-0.5PT） （x=0.00, 0.05, 0.10, 0.15, 0.20） multiferroic composites were pre- pared by conventional solid state reaction method. Structural characterization was performed by X-ray diffraction and the mate- rials showed tetragonal structure at room temperature. Surface morphology of the composites was studied by a scanning electron microscope （SEM）. Frequency and temperature dependence of dielectric constant （er） and dielectric loss （tan~） of 0.5BDxF1_x- 0.5PT were measured in a wide range of frequency （100 Hz to 1 MHz） and temperature （25 to 400 ~C）. The analysis of the study showed that the er and tang decreased with increasing frequency in the given range for all the samples which could be explained through the occurrence of dipole relaxation process. The effect of substitution of rare earth element dysprosium （Dy） showed increase in er in all the samples prepared for different concentrations from 0.00 to 0.20. An explanation for high value of er for Dy modified 0.5BiFeO3-0.5PbTiO3 （0.5BF-0.5PT） compared to Gd modified 0.5BF-0.5PT was provided. The variation of AC conductivity with inverse temperature found to obey the Arrhenius equation and the composites showed negative temperature coefficient of resistance （NTCR） behavior. The activation energy was found to be in the range from 0.25 to 0.40 eV for all the studied samples.展开更多
The polycrystalline Na_(2)SmV_(5)O_(15)(NSV),a new member of the tungsten bronze(TB)family,was prepared by a mixed-oxide technique.The room-temperature X-ray diffraction(XRD)confirmed the formation of single phase com...The polycrystalline Na_(2)SmV_(5)O_(15)(NSV),a new member of the tungsten bronze(TB)family,was prepared by a mixed-oxide technique.The room-temperature X-ray diffraction(XRD)confirmed the formation of single phase compound with orthorhombic crystal structure.The scanning electron microscopy(SEM)analysis indicated that the compound has homogeneous micrograph with a uniform distribution of small grains over the entire surface of the sample.The analysis of impedance spectra of NSV in a low-temperature range(-100℃to 100℃)at different frequencies exhibited interesting electrical properties like the contribution of bulk effect in conduction process.The study of imaginary part of the impedance at different temperatures showed existence of relaxation peak with its shift towards higher frequency on increasing temperature.This suggested the presence of frequency and temperature dependent relaxation process in the material.The loss peak spectra were found to abide by Arrhenius law with small activation energy of 0.12 eV.The temperature dependence of AC and DC electrical conductivity(σ_(AC) and σ_(DC))was also obtained.展开更多
The polycrystalline sample of LiSr2Nb5O15(LSN)was prepared by a high-temperature solid state reaction technique.The impedance parameters were studied using an impedance analyzer in a wide range of frequencies(102-106 ...The polycrystalline sample of LiSr2Nb5O15(LSN)was prepared by a high-temperature solid state reaction technique.The impedance parameters were studied using an impedance analyzer in a wide range of frequencies(102-106 Hz)at different temperatures(28-500℃).Nyquist plot reveals the presence of bulk effect only.The bulk resistance of the compound decreases with rise in temperature which shows the negative temperature coefficient of resistance(NTCR)like a semiconductor.The ac conductivity spectrum was found to obey Jonscher’s universal power law.DC conductivity(bulk)with temperature demonstrates that the compound exhibits Arrhenius type of electrical conductivity and the activation energy found to be 0.97 eV.展开更多
The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5（Bi LaxFe1-xO3）–0.5（Pb Ti O3）（x = 0.05,0.10,0.15,0.20）（BLxF1-x-PT） were prepared by mixed oxide method.Structural characterization was per...The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5（Bi LaxFe1-xO3）–0.5（Pb Ti O3）（x = 0.05,0.10,0.15,0.20）（BLxF1-x-PT） were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La（x = 0.05–0.20） concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range（102–106Hz） at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures（200–300 ℃）.展开更多
基金the SERB under DST Fast Track Scheme for Young Scientist (Project No. SR/FTP/PS-036/2011) New Delhi, IndiaCSIR for sanction of Emeritus Scientist scheme (Project No. 21(0944)/12/EMR-II)
文摘0.5BiDyxFe1-xO3-0.5PbTiOa（0.5BDxF1-x-0.5PT） （x=0.00, 0.05, 0.10, 0.15, 0.20） multiferroic composites were pre- pared by conventional solid state reaction method. Structural characterization was performed by X-ray diffraction and the mate- rials showed tetragonal structure at room temperature. Surface morphology of the composites was studied by a scanning electron microscope （SEM）. Frequency and temperature dependence of dielectric constant （er） and dielectric loss （tan~） of 0.5BDxF1_x- 0.5PT were measured in a wide range of frequency （100 Hz to 1 MHz） and temperature （25 to 400 ~C）. The analysis of the study showed that the er and tang decreased with increasing frequency in the given range for all the samples which could be explained through the occurrence of dipole relaxation process. The effect of substitution of rare earth element dysprosium （Dy） showed increase in er in all the samples prepared for different concentrations from 0.00 to 0.20. An explanation for high value of er for Dy modified 0.5BiFeO3-0.5PbTiO3 （0.5BF-0.5PT） compared to Gd modified 0.5BF-0.5PT was provided. The variation of AC conductivity with inverse temperature found to obey the Arrhenius equation and the composites showed negative temperature coefficient of resistance （NTCR） behavior. The activation energy was found to be in the range from 0.25 to 0.40 eV for all the studied samples.
文摘The polycrystalline Na_(2)SmV_(5)O_(15)(NSV),a new member of the tungsten bronze(TB)family,was prepared by a mixed-oxide technique.The room-temperature X-ray diffraction(XRD)confirmed the formation of single phase compound with orthorhombic crystal structure.The scanning electron microscopy(SEM)analysis indicated that the compound has homogeneous micrograph with a uniform distribution of small grains over the entire surface of the sample.The analysis of impedance spectra of NSV in a low-temperature range(-100℃to 100℃)at different frequencies exhibited interesting electrical properties like the contribution of bulk effect in conduction process.The study of imaginary part of the impedance at different temperatures showed existence of relaxation peak with its shift towards higher frequency on increasing temperature.This suggested the presence of frequency and temperature dependent relaxation process in the material.The loss peak spectra were found to abide by Arrhenius law with small activation energy of 0.12 eV.The temperature dependence of AC and DC electrical conductivity(σ_(AC) and σ_(DC))was also obtained.
基金The authors(PN and BB)acknowledge the financial support through DRS-I under SAP of UGC for the development of research work in the School of Physics,SU.
文摘The polycrystalline sample of LiSr2Nb5O15(LSN)was prepared by a high-temperature solid state reaction technique.The impedance parameters were studied using an impedance analyzer in a wide range of frequencies(102-106 Hz)at different temperatures(28-500℃).Nyquist plot reveals the presence of bulk effect only.The bulk resistance of the compound decreases with rise in temperature which shows the negative temperature coefficient of resistance(NTCR)like a semiconductor.The ac conductivity spectrum was found to obey Jonscher’s universal power law.DC conductivity(bulk)with temperature demonstrates that the compound exhibits Arrhenius type of electrical conductivity and the activation energy found to be 0.97 eV.
基金support through DRS-I of UGC under SAP,School of Physics,Sambalpur University,UGC-Rajiv Gandhi National Fellowship scheme,UGCBSR fellowship scheme,SERB under DST Fast Track Scheme for Young Scientist (Project No.SR/FTP/PS-036/2011)New Delhi,India,and CSIR for sanction of Emeritus Scientist scheme (Project No.21(0944)/12/EMR-Ⅱ)
文摘The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5（Bi LaxFe1-xO3）–0.5（Pb Ti O3）（x = 0.05,0.10,0.15,0.20）（BLxF1-x-PT） were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La（x = 0.05–0.20） concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range（102–106Hz） at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures（200–300 ℃）.
