Tin oxide (SnO<sub>2</sub>) nanofibers are successfully prepared by electrospinning homogeneous viscous solutions of tin acetate in polyvinylpyrrolidone (PVP). The electrospinning is carried out by applyin...Tin oxide (SnO<sub>2</sub>) nanofibers are successfully prepared by electrospinning homogeneous viscous solutions of tin acetate in polyvinylpyrrolidone (PVP). The electrospinning is carried out by applying a DC voltage to the tip of a syringe and maintaining the tip to collector distance (TCD), i.e. at DC electric field of 1.25 kV•cm<sup>–</sup>1. The electrospun nanofibers are calcined between 550℃ and 650℃ for 4 h. Both spun and heat treated nanofibers are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra red spectroscopy (FTIR) etc. XRD analysis of calcined nanofibers confirms the formation of pure tin oxide. TEM study showed that fibers have a polycrystalline structure with multiple nano-grains.展开更多
The nanocrystalline ferroelectric LiNbO3 films on（001） Si substrates with the random orientation of polycrystalline grains and the predominance of the grains with lateral orientation of the polar axis were grown usi...The nanocrystalline ferroelectric LiNbO3 films on（001） Si substrates with the random orientation of polycrystalline grains and the predominance of the grains with lateral orientation of the polar axis were grown using the ion beam sputtering method. The remanent polarization and the coercive field are 12 μC/cm2and 29 kV/cm, respectively. The thermal annealing leads to the coarsening of the grains. The appearance of the ＂local texture,＂ which gives rise to the unipolarity of the heterostructures caused by the predominance of the one direction in the vertical component of the spontaneous polarization, is investigated.展开更多
Sodium potassium niobate (KNN) (K0.5Na0.5NbO3) nanopowder with a mean particle size of about 20 - 30 nm was synthesized by wet chemical route using Nb2O5 as Nb source. A solution of K, Na and Nb cations was prepared, ...Sodium potassium niobate (KNN) (K0.5Na0.5NbO3) nanopowder with a mean particle size of about 20 - 30 nm was synthesized by wet chemical route using Nb2O5 as Nb source. A solution of K, Na and Nb cations was prepared, which resulted in a clear gel after the thermal treatment. Phase analysis, microstructure and morphology of the powder were determined by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Field Emission Scanning Electron Microscopy (FESEM). The obtained gel was first analyzed by Thermo Gravimetric Analyzer (TGA) and Differential Scanning Calorimetry (DSC), and then calcined at different temperatures of 400℃, 500℃, 600℃ and 700℃. The X-Ray Diffraction (XRD) patterns of the synthesized samples confirmed the formation of the orthorhombic crystal phase of K0.5Na0.5NbO3 at 500?C, a temperature significantly lower than that typically used in the conventional mixed oxide route. The process developed in this work is convenient to realize the mass production of KNN nanopowders at low cost and suitable for various industrial applications.展开更多
The formation and evolution of the self-assembled nanodomain structures during polarization reversal have been comparatively analyzed in single crystals of various uniaxial ferroelectrics:LiNbO_(3)(LN),LiTaO_(3)(LT)an...The formation and evolution of the self-assembled nanodomain structures during polarization reversal have been comparatively analyzed in single crystals of various uniaxial ferroelectrics:LiNbO_(3)(LN),LiTaO_(3)(LT)and Sr_(x)Ba_(1-x)Nb_(2)O_(6)(SBN).Several experimental methods have been used for visualization of the micro-and nanodomain patterns.The static domain images have been obtained by optical microscopy and piezoresponse force microscopy.The Raman confocal microscopy allowed us to obtain the domain images in the bulk.The equilibrium slow switching with effective screening resulted in growth of polygon-shaped microdomains:hexagons in LN,triangles in LT and squares in SBN,which corresponds to crystal symmetry.Switching in nonequilibrium conditions(noneffective screening of depolarization field)brings to appearance of similar nanodomain structures in all studied crystals as a result of different processes:(1)formation of nanodomain ensembles,(2)discrete switching,(3)incomplete merging and(4)spontaneous backswitching.展开更多
In this paper,we present impedance spectroscopy of Sodium Bismuth Titanate-based materials belonging to(1-x)TNa_(1/2)Bi_(1/2)TiO_(3)-xBaTiO_(3)(x=0.04)(NBT-BT)system.NBT-BT ceramics are prepared by high temperature so...In this paper,we present impedance spectroscopy of Sodium Bismuth Titanate-based materials belonging to(1-x)TNa_(1/2)Bi_(1/2)TiO_(3)-xBaTiO_(3)(x=0.04)(NBT-BT)system.NBT-BT ceramics are prepared by high temperature solid-state reaction method.X-ray diffraction technique showed single-phase polycrystalline sample with an ABO3 perovskite structure.Dielectric behavior and the impedance relaxation were investigated in a wide range of temperature(room temperature(RT)-500℃)and frequency(1 kHz-1 MHz).A broad dielectric constant peak was observed over a wide temperature range around the phase transition temperature.The complex impedance plot exhibited one impedance semicircle identified over the frequency range of 1 kHz-1MHz,which is explained by the grain effect of the bulk.The centers of the impedance semicircles lie below the real axis,which indicates that the impedance response is a Cole-Cole type relaxation.展开更多
The multiferroic Bi_(0.8)Gd_(0.1)M_(0.1)Fe_(0.9)Ti_(0.1)O_(3),(where M=Ba(DB),La(DL)and Pb(DP))has been synthesized by using solid-state reaction technique.Effects of Ba,La and Pb substitution on the structure,electri...The multiferroic Bi_(0.8)Gd_(0.1)M_(0.1)Fe_(0.9)Ti_(0.1)O_(3),(where M=Ba(DB),La(DL)and Pb(DP))has been synthesized by using solid-state reaction technique.Effects of Ba,La and Pb substitution on the structure,electrical and ferroelectric properties of Bi_(0.8)Gd_(0.1)M_(0.1)Fe_(0.9)Ti_(0.1)O_(3) samples have been studied by performing X-ray diffraction,dielectric and magnetic measurements.The crystal structures of the ceramic samples have a tetragonal phase.The vibrating sample magnetometer(VSM)measurement shows a significant change in the magnetic properties of Ba-doped Bi_(0.8)Gd_(0.1)M_(0.1)Fe_(0.9)Ti_(0.1)O_(3) as compared to La-and Pb-doped ceramics.It is seen that coercive field(HC)and remanent magnetization(MR)increases with Ba-doped ceramics but decreases for La-and Pbdoped ceramics.展开更多
The recent achievements in studying the self-assembled evolution of micro-and nanoscale domain structures in uniaxial single crystalline ferroelectrics lithium niobate and lithium tantalate have been reviewed.The resu...The recent achievements in studying the self-assembled evolution of micro-and nanoscale domain structures in uniaxial single crystalline ferroelectrics lithium niobate and lithium tantalate have been reviewed.The results obtained by visualization of static domain patterns and kinetics of the domain structure by different methods from common optical microscopy to more sophisticated scanning probe microscopy,scanning electron microscopy and confocal Raman microscopy,have been discussed.The kinetic approach based on various nucleation processes similar to the first-order phase transition was used for explanation of the domain structure evolution scenarios.The main mechanisms of self-assembling for nonequilibrium switching conditions caused by screening ineffectiveness including correlated nucleation,domain growth anisotropy,and domain–domain interaction have been considered.The formation of variety of self-assembled domain patterns such as fractal-type,finger and web structures,broad domain boundaries,and dendrites have been revealed at each of all five stages of domain structure evolution during polarization reversal.The possible applications of self-assembling for micro-and nanodomain engineering were reviewed briefly.The review covers mostly the results published by our research group.展开更多
The ability of BaTiO_(3)to form solid solutions with different dopants(both iso-and aliovalent)makes it versatile for various applications.In the present study,(Ba,Ca)TiO_(3)(BCT)is modified with Bi(MgTi)O_(3)(BMT)in ...The ability of BaTiO_(3)to form solid solutions with different dopants(both iso-and aliovalent)makes it versatile for various applications.In the present study,(Ba,Ca)TiO_(3)(BCT)is modified with Bi(MgTi)O_(3)(BMT)in search for new lead-free ferroelectric material and improve their properties.For this purpose,BCT acts as a main base material and BMT acts as a modifier to fabricate a multifunctional material.In this study,we report the structural and electrical properties of lead free piezo-ceramics(1-x)(Ba_(0.8)Ca_(0.2))TiO_(3–x)Bi(Mg_(0.5)Ti_(0.5))O_(3)with x=0.2,0.4,0.5 prepared by solid-state sintering technique.Single perovskite phase with tetragonal structure is obtained for all the compositions,which is reconfirmed by the Raman Spectroscopic study.Dielectric study confirm the temperature stable behavior of the dielectric permittivity values above 300℃.The dielectric constant value decreases with increase in BMT doping content.Impedance Spectroscopic study confirms non-Debye type dielectric relaxation in the specimen.The Nyquist plot and conductivity studies show the negative temperature coefficient of resistance behavior(NTCR)of the samples.展开更多
This work focuses on the structural,electrical and magnetic properties of Bi_(0.8)Tb_(0.1)Ba_(0.1)Fe_(0.9)Ti_(0.1)O_(3)ceramics,fabricated by solid state reaction procedure.XRD forms of the samples at RT exhibited per...This work focuses on the structural,electrical and magnetic properties of Bi_(0.8)Tb_(0.1)Ba_(0.1)Fe_(0.9)Ti_(0.1)O_(3)ceramics,fabricated by solid state reaction procedure.XRD forms of the samples at RT exhibited perovskite phase through the hexagonal structure at room temperature.Dielectric studies of the materials with frequency at different temperatures(25-400℃)exhibit two dielectric anomalies,first at 175℃(ferroelectric-ferroelectric transition)and second at around 320℃(ferroelectric-paraelectric transition).The Curie temperature moved towards the low side temperature with the increase in frequency.The less value of activation energy got for these samples could be attributed to the influence of electronic contribution to the conductivity.A significant change in the magnetic studies was observed for Bi_(0.8)Tb_(0.1)Ba_(0.1)Fe_(0.9)Ti_(0.1)O_(3) ceramic.The impedance analysis confirms the non-Debye type nature of the ceramic and relaxation frequency moved to a higher temperature.The Nyquist plot and conductivity studies showed the NTCR behavior of samples.The highest magnetization field was found at temperature-268.15℃.展开更多
文摘Tin oxide (SnO<sub>2</sub>) nanofibers are successfully prepared by electrospinning homogeneous viscous solutions of tin acetate in polyvinylpyrrolidone (PVP). The electrospinning is carried out by applying a DC voltage to the tip of a syringe and maintaining the tip to collector distance (TCD), i.e. at DC electric field of 1.25 kV•cm<sup>–</sup>1. The electrospun nanofibers are calcined between 550℃ and 650℃ for 4 h. Both spun and heat treated nanofibers are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra red spectroscopy (FTIR) etc. XRD analysis of calcined nanofibers confirms the formation of pure tin oxide. TEM study showed that fibers have a polycrystalline structure with multiple nano-grains.
文摘The nanocrystalline ferroelectric LiNbO3 films on（001） Si substrates with the random orientation of polycrystalline grains and the predominance of the grains with lateral orientation of the polar axis were grown using the ion beam sputtering method. The remanent polarization and the coercive field are 12 μC/cm2and 29 kV/cm, respectively. The thermal annealing leads to the coarsening of the grains. The appearance of the ＂local texture,＂ which gives rise to the unipolarity of the heterostructures caused by the predominance of the one direction in the vertical component of the spontaneous polarization, is investigated.
文摘Sodium potassium niobate (KNN) (K0.5Na0.5NbO3) nanopowder with a mean particle size of about 20 - 30 nm was synthesized by wet chemical route using Nb2O5 as Nb source. A solution of K, Na and Nb cations was prepared, which resulted in a clear gel after the thermal treatment. Phase analysis, microstructure and morphology of the powder were determined by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Field Emission Scanning Electron Microscopy (FESEM). The obtained gel was first analyzed by Thermo Gravimetric Analyzer (TGA) and Differential Scanning Calorimetry (DSC), and then calcined at different temperatures of 400℃, 500℃, 600℃ and 700℃. The X-Ray Diffraction (XRD) patterns of the synthesized samples confirmed the formation of the orthorhombic crystal phase of K0.5Na0.5NbO3 at 500?C, a temperature significantly lower than that typically used in the conventional mixed oxide route. The process developed in this work is convenient to realize the mass production of KNN nanopowders at low cost and suitable for various industrial applications.
文摘The formation and evolution of the self-assembled nanodomain structures during polarization reversal have been comparatively analyzed in single crystals of various uniaxial ferroelectrics:LiNbO_(3)(LN),LiTaO_(3)(LT)and Sr_(x)Ba_(1-x)Nb_(2)O_(6)(SBN).Several experimental methods have been used for visualization of the micro-and nanodomain patterns.The static domain images have been obtained by optical microscopy and piezoresponse force microscopy.The Raman confocal microscopy allowed us to obtain the domain images in the bulk.The equilibrium slow switching with effective screening resulted in growth of polygon-shaped microdomains:hexagons in LN,triangles in LT and squares in SBN,which corresponds to crystal symmetry.Switching in nonequilibrium conditions(noneffective screening of depolarization field)brings to appearance of similar nanodomain structures in all studied crystals as a result of different processes:(1)formation of nanodomain ensembles,(2)discrete switching,(3)incomplete merging and(4)spontaneous backswitching.
文摘In this paper,we present impedance spectroscopy of Sodium Bismuth Titanate-based materials belonging to(1-x)TNa_(1/2)Bi_(1/2)TiO_(3)-xBaTiO_(3)(x=0.04)(NBT-BT)system.NBT-BT ceramics are prepared by high temperature solid-state reaction method.X-ray diffraction technique showed single-phase polycrystalline sample with an ABO3 perovskite structure.Dielectric behavior and the impedance relaxation were investigated in a wide range of temperature(room temperature(RT)-500℃)and frequency(1 kHz-1 MHz).A broad dielectric constant peak was observed over a wide temperature range around the phase transition temperature.The complex impedance plot exhibited one impedance semicircle identified over the frequency range of 1 kHz-1MHz,which is explained by the grain effect of the bulk.The centers of the impedance semicircles lie below the real axis,which indicates that the impedance response is a Cole-Cole type relaxation.
基金Radheshyam Rai is grateful to the Foundation for Science and Technology of Portugal(FCT)for financial support(grant SFRH/BPD/38001/2007).
文摘The multiferroic Bi_(0.8)Gd_(0.1)M_(0.1)Fe_(0.9)Ti_(0.1)O_(3),(where M=Ba(DB),La(DL)and Pb(DP))has been synthesized by using solid-state reaction technique.Effects of Ba,La and Pb substitution on the structure,electrical and ferroelectric properties of Bi_(0.8)Gd_(0.1)M_(0.1)Fe_(0.9)Ti_(0.1)O_(3) samples have been studied by performing X-ray diffraction,dielectric and magnetic measurements.The crystal structures of the ceramic samples have a tetragonal phase.The vibrating sample magnetometer(VSM)measurement shows a significant change in the magnetic properties of Ba-doped Bi_(0.8)Gd_(0.1)M_(0.1)Fe_(0.9)Ti_(0.1)O_(3) as compared to La-and Pb-doped ceramics.It is seen that coercive field(HC)and remanent magnetization(MR)increases with Ba-doped ceramics but decreases for La-and Pbdoped ceramics.
基金made possible by Russian Scientific Foundation(Grant 14-12-00826)in part by Ministry of Education and Science of the Russian Federation(UID RFMEFI59414X0011).
文摘The recent achievements in studying the self-assembled evolution of micro-and nanoscale domain structures in uniaxial single crystalline ferroelectrics lithium niobate and lithium tantalate have been reviewed.The results obtained by visualization of static domain patterns and kinetics of the domain structure by different methods from common optical microscopy to more sophisticated scanning probe microscopy,scanning electron microscopy and confocal Raman microscopy,have been discussed.The kinetic approach based on various nucleation processes similar to the first-order phase transition was used for explanation of the domain structure evolution scenarios.The main mechanisms of self-assembling for nonequilibrium switching conditions caused by screening ineffectiveness including correlated nucleation,domain growth anisotropy,and domain–domain interaction have been considered.The formation of variety of self-assembled domain patterns such as fractal-type,finger and web structures,broad domain boundaries,and dendrites have been revealed at each of all five stages of domain structure evolution during polarization reversal.The possible applications of self-assembling for micro-and nanodomain engineering were reviewed briefly.The review covers mostly the results published by our research group.
文摘The ability of BaTiO_(3)to form solid solutions with different dopants(both iso-and aliovalent)makes it versatile for various applications.In the present study,(Ba,Ca)TiO_(3)(BCT)is modified with Bi(MgTi)O_(3)(BMT)in search for new lead-free ferroelectric material and improve their properties.For this purpose,BCT acts as a main base material and BMT acts as a modifier to fabricate a multifunctional material.In this study,we report the structural and electrical properties of lead free piezo-ceramics(1-x)(Ba_(0.8)Ca_(0.2))TiO_(3–x)Bi(Mg_(0.5)Ti_(0.5))O_(3)with x=0.2,0.4,0.5 prepared by solid-state sintering technique.Single perovskite phase with tetragonal structure is obtained for all the compositions,which is reconfirmed by the Raman Spectroscopic study.Dielectric study confirm the temperature stable behavior of the dielectric permittivity values above 300℃.The dielectric constant value decreases with increase in BMT doping content.Impedance Spectroscopic study confirms non-Debye type dielectric relaxation in the specimen.The Nyquist plot and conductivity studies show the negative temperature coefficient of resistance behavior(NTCR)of the samples.
基金the Defence Research and Development Organisation(DRDO)Govt.of India,for financial support under the research project ERIP/ER/1303129/M/01/1564.
文摘This work focuses on the structural,electrical and magnetic properties of Bi_(0.8)Tb_(0.1)Ba_(0.1)Fe_(0.9)Ti_(0.1)O_(3)ceramics,fabricated by solid state reaction procedure.XRD forms of the samples at RT exhibited perovskite phase through the hexagonal structure at room temperature.Dielectric studies of the materials with frequency at different temperatures(25-400℃)exhibit two dielectric anomalies,first at 175℃(ferroelectric-ferroelectric transition)and second at around 320℃(ferroelectric-paraelectric transition).The Curie temperature moved towards the low side temperature with the increase in frequency.The less value of activation energy got for these samples could be attributed to the influence of electronic contribution to the conductivity.A significant change in the magnetic studies was observed for Bi_(0.8)Tb_(0.1)Ba_(0.1)Fe_(0.9)Ti_(0.1)O_(3) ceramic.The impedance analysis confirms the non-Debye type nature of the ceramic and relaxation frequency moved to a higher temperature.The Nyquist plot and conductivity studies showed the NTCR behavior of samples.The highest magnetization field was found at temperature-268.15℃.
