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 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
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
In this research paper,we utilized the traditional high-temperature solid-state reaction method to fabricate the K_(0.495)Na_(0.520)NbO_(3),K_(0.480)Na_(0.535)NbO_(3)and K_(0.475)Na_(0.540)NbO_(3)(abbreviated as KNN-1...In this research paper,we utilized the traditional high-temperature solid-state reaction method to fabricate the K_(0.495)Na_(0.520)NbO_(3),K_(0.480)Na_(0.535)NbO_(3)and K_(0.475)Na_(0.540)NbO_(3)(abbreviated as KNN-1,KNN-2,and KNN-3,respectively)lead-free ion deficient ceramics for understanding the influence of ionic deficiency on the crystalline structure and dielectric/piezoelectric properties of the samples.X-ray diffraction patterns of these samples exhibited a perovskite tetragonal phase.Dielectric anomalies around 287℃and 471℃were identified as ferroelectric to ferroelectric and ferroelectric to paraelectric-transition temperatures for KNN-2 at 1 kHz.It was found that the composition KNN-2 exhibit relatively high Curie temperature i.e.,471℃.The conductivity plots confirm that the activation energies are frequency-dependent.The impedance behavior in our ceramic samples can be analyzed with the bulk/grain effect.The slope of Z′with temperature shows negative temperature coefficient of resistance(NTCR)type behavior in proposed KNN ceramics material.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
The multiferroic(Bi_(0.95)RE_(0.05))(Fe_(0.95)Mn_(0.05))O_(3)(where RE=Pr,Tb and Dy)has been synthesized using solid-state reaction technique.Effects of Pr,Tb and Dy substitution on the structure,electrical and ferroe...The multiferroic(Bi_(0.95)RE_(0.05))(Fe_(0.95)Mn_(0.05))O_(3)(where RE=Pr,Tb and Dy)has been synthesized using solid-state reaction technique.Effects of Pr,Tb and Dy substitution on the structure,electrical and ferroelectric properties of(Bi_(0.95)RE_(0.05))(Fe_(0.95)Mn_(0.05))O_(3) samples have been studied by performing X-ray diffraction,dielectric measurements and magnetic measurements.The crystal structure of the ceramic samples have a monoclinic phase.The vibrating sample magnetometer(VSM)measurement shows a significant change in the magnetic properties of Pr-,Tb-and Dy-doped(Bi_(0.9)RE_(0.05))(Fe_(0.95)Mn_(0.05))O_(3).It is seen that coercive field(Hc)and remanent magnetization(Mr)increases for Pr but decreases for Dy and Tb.展开更多
Ternary solid solutions of BiFeO_(3),GdFeO_(3)and BaTiO_(3)have been prepared by solid-state reaction method.Dielectric properties of these ceramics have been characterized in the tem-perature range between room tempe...Ternary solid solutions of BiFeO_(3),GdFeO_(3)and BaTiO_(3)have been prepared by solid-state reaction method.Dielectric properties of these ceramics have been characterized in the tem-perature range between room temperature and 673 K and magnetic properties between 5 K and 300K.For the understanding of the multiferroic property,the relation between the crystal structures,magnetic transition and ferroelectric transitions with increasing temperature have been analyzed.All ceramic samples show single perovskite phase.When Ba content exceeds 0.2 wt%,the sintering ability is weakened and the phase structure of Bi_(1-x-y)Gd_(x)Ba_(y)Fe_(1-y)Ti_(y)O_(3)(with x=0.2 and y=0.1,0.2,0.3,0.4,0.5)solid solution changes from rhombohedral to tetragonal phase.The maximum ferroelectric transition temperature(T_(c))of this system was in the range 154-165℃with the dielectric constant peak of 6000 for y=0.5 at 100 kHz.Well-saturated piezoresponse hysteresis loops were observed for all compositions indicating room temperature ferroelectricity.With increasing Ba content(up to 0.3 wt%)the remanent magnetization M,increased and the coercive magnetic field decreased.展开更多
In this paper,we investigated the influence of rare earth(RE=La and Gd)doped Ba_(0.9575)RE_(0.04)Ca_(0.0025)Ti_(0.80685)Mn_(0.002475)Nb_(0.002475)Zr_(0.1782)O_(3)(BCTMNZ)ceramics were fabricated by using a conventiona...In this paper,we investigated the influence of rare earth(RE=La and Gd)doped Ba_(0.9575)RE_(0.04)Ca_(0.0025)Ti_(0.80685)Mn_(0.002475)Nb_(0.002475)Zr_(0.1782)O_(3)(BCTMNZ)ceramics were fabricated by using a conventional solid state reaction method.The doping effects of La and Gd on the structural and magnetic properties were studied.The structural pattern of the ceramic samples were investigated by X-ray diffraction and the results indicated that both samples shows an orthorhombic structure with pure phase.Strain and crystalline size values for Gd and La doped were 0.31-0.33%and 0.154-0.181μm,respectively.The room temperature hysteresis loops were obtained by using a vibrating sample magnetometer.La doped ceramic showed the higher value of mag-netization i.e.,0.369μB/f.u.as compared to Gd doped BLTMNZ ceramics.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
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.
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℃.
基金the DST(INT/RUS/RFBR/P-299)New DelhiRFBR(#17-58-45026 IND_a)Moscow for financial support.
文摘In this research paper,we utilized the traditional high-temperature solid-state reaction method to fabricate the K_(0.495)Na_(0.520)NbO_(3),K_(0.480)Na_(0.535)NbO_(3)and K_(0.475)Na_(0.540)NbO_(3)(abbreviated as KNN-1,KNN-2,and KNN-3,respectively)lead-free ion deficient ceramics for understanding the influence of ionic deficiency on the crystalline structure and dielectric/piezoelectric properties of the samples.X-ray diffraction patterns of these samples exhibited a perovskite tetragonal phase.Dielectric anomalies around 287℃and 471℃were identified as ferroelectric to ferroelectric and ferroelectric to paraelectric-transition temperatures for KNN-2 at 1 kHz.It was found that the composition KNN-2 exhibit relatively high Curie temperature i.e.,471℃.The conductivity plots confirm that the activation energies are frequency-dependent.The impedance behavior in our ceramic samples can be analyzed with the bulk/grain effect.The slope of Z′with temperature shows negative temperature coefficient of resistance(NTCR)type behavior in proposed KNN ceramics material.
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_(0.95)RE_(0.05))(Fe_(0.95)Mn_(0.05))O_(3)(where RE=Pr,Tb and Dy)has been synthesized using solid-state reaction technique.Effects of Pr,Tb and Dy substitution on the structure,electrical and ferroelectric properties of(Bi_(0.95)RE_(0.05))(Fe_(0.95)Mn_(0.05))O_(3) samples have been studied by performing X-ray diffraction,dielectric measurements and magnetic measurements.The crystal structure of the ceramic samples have a monoclinic phase.The vibrating sample magnetometer(VSM)measurement shows a significant change in the magnetic properties of Pr-,Tb-and Dy-doped(Bi_(0.9)RE_(0.05))(Fe_(0.95)Mn_(0.05))O_(3).It is seen that coercive field(Hc)and remanent magnetization(Mr)increases for Pr but decreases for Dy and Tb.
基金Radheshyam Rai is grateful to the Foundation for Science and Technology of Portugal(FCT)fornan-cial support(Grant No.SFRH/BPD/38001/2007).
文摘Ternary solid solutions of BiFeO_(3),GdFeO_(3)and BaTiO_(3)have been prepared by solid-state reaction method.Dielectric properties of these ceramics have been characterized in the tem-perature range between room temperature and 673 K and magnetic properties between 5 K and 300K.For the understanding of the multiferroic property,the relation between the crystal structures,magnetic transition and ferroelectric transitions with increasing temperature have been analyzed.All ceramic samples show single perovskite phase.When Ba content exceeds 0.2 wt%,the sintering ability is weakened and the phase structure of Bi_(1-x-y)Gd_(x)Ba_(y)Fe_(1-y)Ti_(y)O_(3)(with x=0.2 and y=0.1,0.2,0.3,0.4,0.5)solid solution changes from rhombohedral to tetragonal phase.The maximum ferroelectric transition temperature(T_(c))of this system was in the range 154-165℃with the dielectric constant peak of 6000 for y=0.5 at 100 kHz.Well-saturated piezoresponse hysteresis loops were observed for all compositions indicating room temperature ferroelectricity.With increasing Ba content(up to 0.3 wt%)the remanent magnetization M,increased and the coercive magnetic field decreased.
基金Authors are grateful to the Defense Research and Development Organization(DRDO),Govt.of India,for financial support under the research project ERIP/ER/1303129/M/01/1564.
文摘In this paper,we investigated the influence of rare earth(RE=La and Gd)doped Ba_(0.9575)RE_(0.04)Ca_(0.0025)Ti_(0.80685)Mn_(0.002475)Nb_(0.002475)Zr_(0.1782)O_(3)(BCTMNZ)ceramics were fabricated by using a conventional solid state reaction method.The doping effects of La and Gd on the structural and magnetic properties were studied.The structural pattern of the ceramic samples were investigated by X-ray diffraction and the results indicated that both samples shows an orthorhombic structure with pure phase.Strain and crystalline size values for Gd and La doped were 0.31-0.33%and 0.154-0.181μm,respectively.The room temperature hysteresis loops were obtained by using a vibrating sample magnetometer.La doped ceramic showed the higher value of mag-netization i.e.,0.369μB/f.u.as compared to Gd doped BLTMNZ ceramics.
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.