Single-phase multiferroic BiFeO3 and rare-earth metal of holmium (Ho) doped BiFeO3 nanofilms were prepared on Pt (100)/Ti/SiO2/Si wafer via solution-gelation technique. It was suggested that the lattice distortion...Single-phase multiferroic BiFeO3 and rare-earth metal of holmium (Ho) doped BiFeO3 nanofilms were prepared on Pt (100)/Ti/SiO2/Si wafer via solution-gelation technique. It was suggested that the lattice distortion happened with the lattice parameter of d decreasing after doping rare-earth metal of Ho. Meanwhile, the structure of nanofilms transformed from hexahedron phase to tetragonal phase after doping Ho. The analysis on X-ray photoelectron spectroscopy (XPS) indicated that the ratio of Fe3~ cations to Fe2+ cations increased with the increase of binding energy between Fe and O and decrease of that between Bi and O after doping Ho. The present work provided an available way on enhancing multiferroic of BiFeO3 nanofilms.展开更多
Multiferroic BiFeO_(3)-based ceramics were synthesized using the rapid liquid-phase sintering method.The rare-earth ion(Sm^(3+),Gd^(3+),Y^(3+))doping causes structural distortion without changing the intrinsic rhomboh...Multiferroic BiFeO_(3)-based ceramics were synthesized using the rapid liquid-phase sintering method.The rare-earth ion(Sm^(3+),Gd^(3+),Y^(3+))doping causes structural distortion without changing the intrinsic rhombohedral perovskite structure.Raman analysis shows that the effect of doping on E modes is greater than A1 modes,and the microstructure of FeO_(6) octahedron can be regulated by ion doping.A-site trivalent ion doped ceramics exhibit improved magnetism compared with pure BiFeO_(3) ceramic,which originated from the suppressed spiral spin structure of Fe ions.The tilt of FeO_(6) octahedron as a typical structure instability causes the anomalous change of the imaginary part of permittivity at high frequency,and doped ceramics exhibit natural resonance around 16-17 GHz.展开更多
The main focus of the research was to correlate the microstructure with dielectric and magnetic properties of Bi1-xBaxFeO3 samples. Bi1-xBaxFeO3 samples(x = 0.1, 0.2 and 0.3) were synthesized by the conventional sol...The main focus of the research was to correlate the microstructure with dielectric and magnetic properties of Bi1-xBaxFeO3 samples. Bi1-xBaxFeO3 samples(x = 0.1, 0.2 and 0.3) were synthesized by the conventional solid-state reaction method using nano-powders of Bi2O3, Fe2O3, and BaCO3. Thereafter, field emission scanning electron microscope and X-ray diffraction(XRD) techniques were used to examine the structure and phase of the samples. Phase analysis by XRD indicated that the single-phase perovskite structure was formed with possible increment in lattice parameter with increasing Ba doping. Complex permeability(u'iand u''i) measured using impedance analyzer confirmed the increase in magnetic property with increasing Ba doping. Finally, dielectric constant(k) was analyzed as a function of temperature at different frequencies. Dielectric constant as high as 2900 was attained in this research for Bi0.8Ba0.2FeO3 sample due to reduction in leakage current at this composition.展开更多
A coprecipitation/hydrothermal route was utilized to fabricate pure phase BiFeO3 powders using FeCl3·6H2O and Bi(NO3)3·5H2O as starting materials, ammonia as precipitant and NaOH as mineralizer. The synthe...A coprecipitation/hydrothermal route was utilized to fabricate pure phase BiFeO3 powders using FeCl3·6H2O and Bi(NO3)3·5H2O as starting materials, ammonia as precipitant and NaOH as mineralizer. The synthesized powders were characterized by XRD, SEM and DSC-TG analysis. In the process, single-phase BiFeO3 powders could be obtained at a hydrothermal reaction temperature of 180 ℃, with NaOH of 0.15 mol/L, in contrast to 200 ℃ and 4 mol/L for conventional hydrothermal route. Meanwhile, the micro-morphology of synthesized BiFeO3 powders changed with different reaction temperatures and concentrations of NaOH. The N6el temperature, Curie temperature and decomposition temperature of the synthesized BiFeO3 powders were detected to be 301 ℃, 828 ℃ and 964 ℃, respectively. The hydrothermal reactions mechanism to fabricate BiFeO3 powders were discussed based on the in-situ transformation process.展开更多
In this research work, (Bi<sub>2</sub>O<sub>3</sub>Fe<sub>2</sub>O<sub>3</sub>)<sub>0.4</sub>(Nb<sub>2</sub>O<sub>5</sub>)<sub>...In this research work, (Bi<sub>2</sub>O<sub>3</sub>Fe<sub>2</sub>O<sub>3</sub>)<sub>0.4</sub>(Nb<sub>2</sub>O<sub>5</sub>)<sub>0.6</sub> was made by the solid state reaction method. Samples were sintered at four different temperatures (850°C, 925°C, 1000°C and 1150°C) to study the effect of sintering temperature on the various properties of the samples. X-ray diffraction analysis confirmed that single phase Bi<sub>1.721</sub>δ<sub>0.089</sub>Fe<sub>1.056</sub>Nb<sub>1.134</sub>O<sub>7</sub> was found when sintering temperature increased. At the same time, larger grain size was found when sintering temperature increased. From variation of dielectric loss with respect to frequency, a small peak was found when sample was sintered at higher temperature (1150°C). Dielectric constant of the sample decreases with the increase of frequency for all the samples. With the variation of temperature, DC resistivity of the samples showed that resistivity decreases with the increase of measuring temperature which indicates semiconducting nature.展开更多
Single-phase multiferroic BiFeO3 and Bi(0.9)(La/Nd)(0.1)FeO3(doped with rare earth ions La-(3+) and Nd-(3+)) films grown on(111)-Pt/Ti/SiO2/Si substrate were prepared via sol-gel method and a subsequen...Single-phase multiferroic BiFeO3 and Bi(0.9)(La/Nd)(0.1)FeO3(doped with rare earth ions La-(3+) and Nd-(3+)) films grown on(111)-Pt/Ti/SiO2/Si substrate were prepared via sol-gel method and a subsequent rapid thermal process. The phase composition, microstructure, ferroelectric, dielectric, ferromagnetic properties were investigated, and meanwhile, the in-plane magnetoelectric(ME) coupling effects of the films were reported and studied for the first time in this work. Structural characterization by X-ray diffraction and scanning electron microscopy showed that both BiFeO3 and Bi(0.9)(La/Nd)(0.1)FeO3 exhabited a rhombohedral structure with(111) preferred orientation. The results of the physical properties indicated that the introduction of rare earth ions improved significantly the polarization, magnetization and dielectric properties than the undoped BiFeO3 crystals, and it enhanced effectively the in-plane ME coupling(the ME coupling coefficient αE increased from 0.13 in the pure BiFeO3 to 0.21 in Bi(0.9)La(0.1)FeO3 and 0.34 V/(Oe·cm) in Bi(0.9)Nd(0.1)FeO3). The mechanism of these phenomena was investigated systematically.展开更多
Bismuth ferrite(BiFeO3)-based materials are multiferroic materials widely studied.This study reports that strong ferroelectricity and enhanced magnetic performance are simultaneously obtained in the quenched(1−x)BiFeO...Bismuth ferrite(BiFeO3)-based materials are multiferroic materials widely studied.This study reports that strong ferroelectricity and enhanced magnetic performance are simultaneously obtained in the quenched(1−x)BiFeO3−xBaTiO3(BFBT100x,x=0.2 and 0.3)ceramics.Quenching treatment can reduce the amount of defects and Fe2+ions and make the defect dipole in a random state,which is conducive to improving the ferroelectricity and magnetism.Compared with the conventional sintered samples,the quenched ceramics have higher remnant and saturation polarization.As for magnetism,the coercive field(Hc)of the quenched ceramics is smaller and the quenching treatment can increase the maximum magnetization by up to 15%.展开更多
A novel two-phase composite film is prepared by the solvent casting method employing poly(methyl methacrylate) (PMMA) as polymer matrix and bismuth ferrite (BFO) as ceramic filler. The surfaces of BFO are functi...A novel two-phase composite film is prepared by the solvent casting method employing poly(methyl methacrylate) (PMMA) as polymer matrix and bismuth ferrite (BFO) as ceramic filler. The surfaces of BFO are functionalized by proper hydroxylating agents to activate their chemical nature. The structural analysis of the composite films confirms that the composites made up of functionalized BFO (BFO-OH) have a distorted rhombohedral structure. The morphological analysis shows that BFO- OH particles are equally distributed over the polymer matrix. The -OH functionality of BFO-OH is confirmed by FTIR. The dielectric and electrical studies at a frequency range from 100 Hz to I MHz reveal that PMMA-(BFO-OH) composites have enhanced dielectric constant as well as electrical conductivities, much higher than that of unmodified composites. According to the ferroelectric measurement result, the hydroxylated composite film shows a superior ferroelectric behavior than that of the unmodified one, with a remanent polarization (2Pr) of 2.764μC/cm2,展开更多
In this review,the state of the art in understanding the structural phase relations in perovskite-structured BiFeO_(3)-based polycrystalline solid solutions is presented and discussed.Issues about the close relation b...In this review,the state of the art in understanding the structural phase relations in perovskite-structured BiFeO_(3)-based polycrystalline solid solutions is presented and discussed.Issues about the close relation between the structural phase and overall physical properties of the reviewed systems are pointed out and discussed.It is shown that,by adjusting the structural symmetric arrangement,the ferroelectric and magnetic properties of BiFeO_(3)-based polycrystalline solid solutions can be tuned to find specific multifunctional applications.However,an intrinsic mechanism linking structural arrangement and physical properties cannot be identified,revealing that this subject still deserves further discussion and investigation.展开更多
Porous bismuth ferrite ceramics were synthesized by sacrificial pore former method. A mixture of BiFeO3 and 20 wt% of various pore formers including high density polyethylene, polyethylene glycol, polyvinyl alcohol, u...Porous bismuth ferrite ceramics were synthesized by sacrificial pore former method. A mixture of BiFeO3 and 20 wt% of various pore formers including high density polyethylene, polyethylene glycol, polyvinyl alcohol, urea and graphite was intensively milled for 10 h in a planetary ball mill, uniaxially cold pressed and then subjected to the multi-stage heat treatment. The results revealed that urea and polyvinyl alcohol are appropriate candidates for maintaining the strength of the final porous structure. Density and porosity measurements showed that by employing 20 wt% of high density polyethylene and graphite, a porous sample with a maximum porosity of nearly 40% could be obtained. Mercury porosimetry results showed that using urea as a pore former gives porous bismuth ferrite with a mean pore diameter of 7μm, uniform pore distribution as well as interconnected pores. Moreover, reactions between BiFeO3 matrix phase and thermal decomposition products of pore formers can lead to degradation of the BiFeO3 phase in the final porous samples. Analysis of X-ray diffraction patterns illustrated that in the samples pro- cessed with graphite, high density polyethylene and polyvinyl alcohol as pore former, BiFeO3 matrix phase partially or completely decomposed to intermediate phases of Bi2Fe4O9 and Bi25FeO40. Using of urea did not damage the matrix phase and porous BiFeO3 within the original perovskite structure could be prepared. Furthermore, thermodynamic investigation was carried out for prediction of possible in- teractions between matrix phase and pore former at elevated temperatures.展开更多
The paper presents the results of a comprehensive study of the thermophysical properties(thermal conductivity,thermal diffusivity,heat capacity)of high-temperature multiferroic BiFeO_(3) modified with rare-earth eleme...The paper presents the results of a comprehensive study of the thermophysical properties(thermal conductivity,thermal diffusivity,heat capacity)of high-temperature multiferroic BiFeO_(3) modified with rare-earth elements(REEs)(La,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Lu).The regularities of the formation of the mentioned characteristics were established.The assumptions about the nature of the observed phenomena were suggested.展开更多
The BiFeO3-based film is one of the most promising candidates for lead-free piezoelectric film devices.In this work,the 1μm-thick Bi(Fe_(0.93)Mn_(0.05)Ti_(0.02))O_(3)(BFMT)films are grown on the ITO/glass substrate u...The BiFeO3-based film is one of the most promising candidates for lead-free piezoelectric film devices.In this work,the 1μm-thick Bi(Fe_(0.93)Mn_(0.05)Ti_(0.02))O_(3)(BFMT)films are grown on the ITO/glass substrate using a sol-gel method combined with spin-coating and layer-by-layer annealing technique.These films display a large saturated polarization of 95μC/cm^(2),and a remanent polarization of 70μC/cm^(2).Especially,the films are self-poled caused by an internal bias field,giving rise to asymmetric polarization-electric field(P-E)loops with a positive shift along the x-axis.A stable self-polarization state is maintained during the applied electric field increasing to 1500 kV/cm and then decreasing back.The weak dependence of P-E loops on frequency(1-50 kHz)and temperature(25-125°C)indicate that the internal bias field can be stable within a certain frequency and temperature range.These results demonstrate that the self-polarized BFMT thick films can be integrated into devices without any poling process,with promising applications in micro-electro-mechanical systems.展开更多
Conventional solid state reaction method,from oxides and carbonates,was employed to prepare bismuth(Bi)-based multiferroic systems.The undoped BiFeO_(3)(BFO)and the codoped system with Ba,La and Ti(Bi_(1-x)Ba_(x)Fe_(1...Conventional solid state reaction method,from oxides and carbonates,was employed to prepare bismuth(Bi)-based multiferroic systems.The undoped BiFeO_(3)(BFO)and the codoped system with Ba,La and Ti(Bi_(1-x)Ba_(x)Fe_(1-y)Ti_(y)O_(3),Bi_(1-x-z)Ba_(x)LazFe_(1-y)TiyO_(3))with x,y,z=0.1 were prepared stoichiometrically and sintered at two different temperatures.The structural and magnetic properties were investigated at room temperature.XRD measurements confirm the obtaining of the rhombohedral perovskite structure of the BFO family system.For the undoped system,some reflections of undesired phases are present for two different sintering temperatures,while for the doped system only one phase is present for both temperatures.The magnetic characterization at room temperature revealed remarkable differences between the ceramic samples.The results show that for undoped BFO system,spontaneous magnetization is not observed at room temperature.Nevertheless,in doped one,a well-defined ferromagnetic behavior is observed at room temperature,possible,due to the suppression of the spatially modulated spin structure of BFO promoted by the reduction of the rhombohedral distortion and the weakening of the Bi-O bonds.The XPS results confirm the presence of oxygen vacancies and the coexistence of Fe^(3+)and Fe^(2+) in all the studied samples.Calorimetric measurements reveal that the dopant incorporation has not a direct effect in Neel temperature but possibly yes in ferroelectric-paraelectric transition.展开更多
基金Project supported by National Key Projects for Basic Research of China(2012CB626815)the National Natural Science Foundation of China(11264026,10904065)+1 种基金Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(NJYT-12-B05)Inner Mongolia Science Foundation for Distinguished Young Scholars(2014JQ01)
文摘Single-phase multiferroic BiFeO3 and rare-earth metal of holmium (Ho) doped BiFeO3 nanofilms were prepared on Pt (100)/Ti/SiO2/Si wafer via solution-gelation technique. It was suggested that the lattice distortion happened with the lattice parameter of d decreasing after doping rare-earth metal of Ho. Meanwhile, the structure of nanofilms transformed from hexahedron phase to tetragonal phase after doping Ho. The analysis on X-ray photoelectron spectroscopy (XPS) indicated that the ratio of Fe3~ cations to Fe2+ cations increased with the increase of binding energy between Fe and O and decrease of that between Bi and O after doping Ho. The present work provided an available way on enhancing multiferroic of BiFeO3 nanofilms.
基金supported by the National Natural Science Foundation of China(51502054)the Postdoctoral Science Foundation of China(2014M551236)the Postdoctoral Science Foundation of Heilongjiang Province(LBH-Z14083).
文摘Multiferroic BiFeO_(3)-based ceramics were synthesized using the rapid liquid-phase sintering method.The rare-earth ion(Sm^(3+),Gd^(3+),Y^(3+))doping causes structural distortion without changing the intrinsic rhombohedral perovskite structure.Raman analysis shows that the effect of doping on E modes is greater than A1 modes,and the microstructure of FeO_(6) octahedron can be regulated by ion doping.A-site trivalent ion doped ceramics exhibit improved magnetism compared with pure BiFeO_(3) ceramic,which originated from the suppressed spiral spin structure of Fe ions.The tilt of FeO_(6) octahedron as a typical structure instability causes the anomalous change of the imaginary part of permittivity at high frequency,and doped ceramics exhibit natural resonance around 16-17 GHz.
文摘The main focus of the research was to correlate the microstructure with dielectric and magnetic properties of Bi1-xBaxFeO3 samples. Bi1-xBaxFeO3 samples(x = 0.1, 0.2 and 0.3) were synthesized by the conventional solid-state reaction method using nano-powders of Bi2O3, Fe2O3, and BaCO3. Thereafter, field emission scanning electron microscope and X-ray diffraction(XRD) techniques were used to examine the structure and phase of the samples. Phase analysis by XRD indicated that the single-phase perovskite structure was formed with possible increment in lattice parameter with increasing Ba doping. Complex permeability(u'iand u''i) measured using impedance analyzer confirmed the increase in magnetic property with increasing Ba doping. Finally, dielectric constant(k) was analyzed as a function of temperature at different frequencies. Dielectric constant as high as 2900 was attained in this research for Bi0.8Ba0.2FeO3 sample due to reduction in leakage current at this composition.
基金the National Natural Science Foundation of China(No.50372039)
文摘A coprecipitation/hydrothermal route was utilized to fabricate pure phase BiFeO3 powders using FeCl3·6H2O and Bi(NO3)3·5H2O as starting materials, ammonia as precipitant and NaOH as mineralizer. The synthesized powders were characterized by XRD, SEM and DSC-TG analysis. In the process, single-phase BiFeO3 powders could be obtained at a hydrothermal reaction temperature of 180 ℃, with NaOH of 0.15 mol/L, in contrast to 200 ℃ and 4 mol/L for conventional hydrothermal route. Meanwhile, the micro-morphology of synthesized BiFeO3 powders changed with different reaction temperatures and concentrations of NaOH. The N6el temperature, Curie temperature and decomposition temperature of the synthesized BiFeO3 powders were detected to be 301 ℃, 828 ℃ and 964 ℃, respectively. The hydrothermal reactions mechanism to fabricate BiFeO3 powders were discussed based on the in-situ transformation process.
文摘In this research work, (Bi<sub>2</sub>O<sub>3</sub>Fe<sub>2</sub>O<sub>3</sub>)<sub>0.4</sub>(Nb<sub>2</sub>O<sub>5</sub>)<sub>0.6</sub> was made by the solid state reaction method. Samples were sintered at four different temperatures (850°C, 925°C, 1000°C and 1150°C) to study the effect of sintering temperature on the various properties of the samples. X-ray diffraction analysis confirmed that single phase Bi<sub>1.721</sub>δ<sub>0.089</sub>Fe<sub>1.056</sub>Nb<sub>1.134</sub>O<sub>7</sub> was found when sintering temperature increased. At the same time, larger grain size was found when sintering temperature increased. From variation of dielectric loss with respect to frequency, a small peak was found when sample was sintered at higher temperature (1150°C). Dielectric constant of the sample decreases with the increase of frequency for all the samples. With the variation of temperature, DC resistivity of the samples showed that resistivity decreases with the increase of measuring temperature which indicates semiconducting nature.
基金Project supported by National Natural Science Foundation of China(51462003)Science Research Fund of Guizhou Province,China(2015-4006,2014-001,2014-7612)+1 种基金the Introduced Talents Funds of Guizhou University(2014-30)Master’s Innovation Funds of Guizhou University(2016065)
文摘Single-phase multiferroic BiFeO3 and Bi(0.9)(La/Nd)(0.1)FeO3(doped with rare earth ions La-(3+) and Nd-(3+)) films grown on(111)-Pt/Ti/SiO2/Si substrate were prepared via sol-gel method and a subsequent rapid thermal process. The phase composition, microstructure, ferroelectric, dielectric, ferromagnetic properties were investigated, and meanwhile, the in-plane magnetoelectric(ME) coupling effects of the films were reported and studied for the first time in this work. Structural characterization by X-ray diffraction and scanning electron microscopy showed that both BiFeO3 and Bi(0.9)(La/Nd)(0.1)FeO3 exhabited a rhombohedral structure with(111) preferred orientation. The results of the physical properties indicated that the introduction of rare earth ions improved significantly the polarization, magnetization and dielectric properties than the undoped BiFeO3 crystals, and it enhanced effectively the in-plane ME coupling(the ME coupling coefficient αE increased from 0.13 in the pure BiFeO3 to 0.21 in Bi(0.9)La(0.1)FeO3 and 0.34 V/(Oe·cm) in Bi(0.9)Nd(0.1)FeO3). The mechanism of these phenomena was investigated systematically.
基金This study was supported by the National Natural Science Foundation of China (51502054)the Postdoctoral Science Foundation of China (2014M551236)the Postdoctoral Science Foundation of Heilongjiang Province (LBH-Z14083).
文摘Bismuth ferrite(BiFeO3)-based materials are multiferroic materials widely studied.This study reports that strong ferroelectricity and enhanced magnetic performance are simultaneously obtained in the quenched(1−x)BiFeO3−xBaTiO3(BFBT100x,x=0.2 and 0.3)ceramics.Quenching treatment can reduce the amount of defects and Fe2+ions and make the defect dipole in a random state,which is conducive to improving the ferroelectricity and magnetism.Compared with the conventional sintered samples,the quenched ceramics have higher remnant and saturation polarization.As for magnetism,the coercive field(Hc)of the quenched ceramics is smaller and the quenching treatment can increase the maximum magnetization by up to 15%.
文摘A novel two-phase composite film is prepared by the solvent casting method employing poly(methyl methacrylate) (PMMA) as polymer matrix and bismuth ferrite (BFO) as ceramic filler. The surfaces of BFO are functionalized by proper hydroxylating agents to activate their chemical nature. The structural analysis of the composite films confirms that the composites made up of functionalized BFO (BFO-OH) have a distorted rhombohedral structure. The morphological analysis shows that BFO- OH particles are equally distributed over the polymer matrix. The -OH functionality of BFO-OH is confirmed by FTIR. The dielectric and electrical studies at a frequency range from 100 Hz to I MHz reveal that PMMA-(BFO-OH) composites have enhanced dielectric constant as well as electrical conductivities, much higher than that of unmodified composites. According to the ferroelectric measurement result, the hydroxylated composite film shows a superior ferroelectric behavior than that of the unmodified one, with a remanent polarization (2Pr) of 2.764μC/cm2,
基金The authors would like to thank the Brazilian Agency Funding CNPq(Proc.476964/2009-1 and 552900/2009-5)CAPES(Procad 082/2007)Fundação Araucária de Apoio ao Desenvolvimento Científico do Paraná(Prots.22825 and 22870)for financial support.
文摘In this review,the state of the art in understanding the structural phase relations in perovskite-structured BiFeO_(3)-based polycrystalline solid solutions is presented and discussed.Issues about the close relation between the structural phase and overall physical properties of the reviewed systems are pointed out and discussed.It is shown that,by adjusting the structural symmetric arrangement,the ferroelectric and magnetic properties of BiFeO_(3)-based polycrystalline solid solutions can be tuned to find specific multifunctional applications.However,an intrinsic mechanism linking structural arrangement and physical properties cannot be identified,revealing that this subject still deserves further discussion and investigation.
基金financial supports of this work by the University of Tehran and Iran Nanotechnology Initiative Council
文摘Porous bismuth ferrite ceramics were synthesized by sacrificial pore former method. A mixture of BiFeO3 and 20 wt% of various pore formers including high density polyethylene, polyethylene glycol, polyvinyl alcohol, urea and graphite was intensively milled for 10 h in a planetary ball mill, uniaxially cold pressed and then subjected to the multi-stage heat treatment. The results revealed that urea and polyvinyl alcohol are appropriate candidates for maintaining the strength of the final porous structure. Density and porosity measurements showed that by employing 20 wt% of high density polyethylene and graphite, a porous sample with a maximum porosity of nearly 40% could be obtained. Mercury porosimetry results showed that using urea as a pore former gives porous bismuth ferrite with a mean pore diameter of 7μm, uniform pore distribution as well as interconnected pores. Moreover, reactions between BiFeO3 matrix phase and thermal decomposition products of pore formers can lead to degradation of the BiFeO3 phase in the final porous samples. Analysis of X-ray diffraction patterns illustrated that in the samples pro- cessed with graphite, high density polyethylene and polyvinyl alcohol as pore former, BiFeO3 matrix phase partially or completely decomposed to intermediate phases of Bi2Fe4O9 and Bi25FeO40. Using of urea did not damage the matrix phase and porous BiFeO3 within the original perovskite structure could be prepared. Furthermore, thermodynamic investigation was carried out for prediction of possible in- teractions between matrix phase and pore former at elevated temperatures.
基金This work was financially supported by the Ministry of Science and Higher Education of the Russian Federation(State assignment in the field of scientific activity,Southern Federal University,2020).
文摘The paper presents the results of a comprehensive study of the thermophysical properties(thermal conductivity,thermal diffusivity,heat capacity)of high-temperature multiferroic BiFeO_(3) modified with rare-earth elements(REEs)(La,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Lu).The regularities of the formation of the mentioned characteristics were established.The assumptions about the nature of the observed phenomena were suggested.
基金supported by the National Natural Science Foundation of China(Grant Nos.51972144,U1806221 and U2006218)the Shandong Provincial Natural Science Foundation(Grant No.ZR2020KA003)+2 种基金the Project of“20 Items of University”of Jinan(Grant Nos.T202009 and T201907)the Introduction Program of Senior Foreign Experts(G2021024003L)the Shandong Provincial Key Research and Development Plan(Grant No.2022CXPT045).
文摘The BiFeO3-based film is one of the most promising candidates for lead-free piezoelectric film devices.In this work,the 1μm-thick Bi(Fe_(0.93)Mn_(0.05)Ti_(0.02))O_(3)(BFMT)films are grown on the ITO/glass substrate using a sol-gel method combined with spin-coating and layer-by-layer annealing technique.These films display a large saturated polarization of 95μC/cm^(2),and a remanent polarization of 70μC/cm^(2).Especially,the films are self-poled caused by an internal bias field,giving rise to asymmetric polarization-electric field(P-E)loops with a positive shift along the x-axis.A stable self-polarization state is maintained during the applied electric field increasing to 1500 kV/cm and then decreasing back.The weak dependence of P-E loops on frequency(1-50 kHz)and temperature(25-125°C)indicate that the internal bias field can be stable within a certain frequency and temperature range.These results demonstrate that the self-polarized BFMT thick films can be integrated into devices without any poling process,with promising applications in micro-electro-mechanical systems.
文摘Conventional solid state reaction method,from oxides and carbonates,was employed to prepare bismuth(Bi)-based multiferroic systems.The undoped BiFeO_(3)(BFO)and the codoped system with Ba,La and Ti(Bi_(1-x)Ba_(x)Fe_(1-y)Ti_(y)O_(3),Bi_(1-x-z)Ba_(x)LazFe_(1-y)TiyO_(3))with x,y,z=0.1 were prepared stoichiometrically and sintered at two different temperatures.The structural and magnetic properties were investigated at room temperature.XRD measurements confirm the obtaining of the rhombohedral perovskite structure of the BFO family system.For the undoped system,some reflections of undesired phases are present for two different sintering temperatures,while for the doped system only one phase is present for both temperatures.The magnetic characterization at room temperature revealed remarkable differences between the ceramic samples.The results show that for undoped BFO system,spontaneous magnetization is not observed at room temperature.Nevertheless,in doped one,a well-defined ferromagnetic behavior is observed at room temperature,possible,due to the suppression of the spatially modulated spin structure of BFO promoted by the reduction of the rhombohedral distortion and the weakening of the Bi-O bonds.The XPS results confirm the presence of oxygen vacancies and the coexistence of Fe^(3+)and Fe^(2+) in all the studied samples.Calorimetric measurements reveal that the dopant incorporation has not a direct effect in Neel temperature but possibly yes in ferroelectric-paraelectric transition.