The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitatio...The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitation method with metal-nitrates as starting materials and mixed alkali (NaOH and Na2CO3) as a precipitating agent. The formation process of LSCCF from the precursors was monitored by TG-DSC, and the crystal structure and particles morphology of the precursors which were calcined at 600, 800, 1000 ℃ for 3 h were characterized using XRD, SEM technologies. Compared with the solid state reaction of constituent oxides, when the pH value of the precipitating solution was in the range of 9.1～9.5, the LSCCF powders from the precursors caclined at 800 ℃ for 3 h had high purity, homogeneous and single perovskite phase. The electrical conductivity of the LSCCF samples sintered at 1200 ℃ for 3 h, which was measured as a function of temperatures from 100 to 800 ℃ by DC four-probe method in air, decreased with x from 0.05 to 0.20. The value of electrical conductivity was almost equal because of Ca2+, Sr2+ co-dopant resulting in the 'mix effect' while x=0.10 or 0.15. The electrical conductivity of all doped samples was higher than 100 S·cm-1 at intermediate temperatures from 500 to 800 ℃, and there was good compatibility between the LSCCF cathode and Ce0.8Sm0.2O2 electrolyte.展开更多
With substitution of La by Tb in (La_(1-x)Tb_x)_(0.67)Sr_(0.33)MnO_3, the room temperature magnetoresistance △R/R_0drops at first, then undergoes an increase near x≈0.1, and finally drops again. The value of room te...With substitution of La by Tb in (La_(1-x)Tb_x)_(0.67)Sr_(0.33)MnO_3, the room temperature magnetoresistance △R/R_0drops at first, then undergoes an increase near x≈0.1, and finally drops again. The value of room temperaturemagnetoresistance at a field H=12 kOe for (La_(0.9)Tb_(0.1))_(0.67)Sr_(0.33)MnO_3 is -3.56%. The enhancement of the roomtemperature magnetoresistance induced by an appropriate Tb substitution in (La_(1-x)Tb_x)_(0.67)Sr_(0.33)MnO_3 is correlatedwith the shifts of the Curie temperature and metal-insulator temperature to near room temperature. The drop ofthe room temperature magnetoresistance at large Tb doping-contents may be due to its lower T_C and T_(MI) far fromthe room temperature.展开更多
In an effort to improve the performance of superconductors in the field and high temperatures it is important to study the superconducting mechanism. For this reason, the cation substitution can be conducted. One of t...In an effort to improve the performance of superconductors in the field and high temperatures it is important to study the superconducting mechanism. For this reason, the cation substitution can be conducted. One of the high Tc superconductors Gd1Ba2Cu3O7−δ phase with Sr substitution has been synthesized, i.e. Gd1(Ba2−xSrx)Cu3O7−δ compound. The sample was synthesized by using a solid-state reaction method with a wet mixing, sintered for 12 hours at temperature 900°C. The synthesis results are characterized by using XRD. The results of Match-3 software analysis showed high (higher 85%) Gd1Ba2Cu3O7−δ phase was formed. The Sr substitution causes changes to the structure, i.e. the lattice parameters a, b and c, where the orthorhombicity tends to decrease with increasing Sr content. Refinement results show that based on the oxygen occupancy, the total oxygen content tends to increase.展开更多
The development of negative permittivity materials in multifunctional applications requests expansion of their operating frequency and improvement of stability of negative permittivity.Low electron density is benefici...The development of negative permittivity materials in multifunctional applications requests expansion of their operating frequency and improvement of stability of negative permittivity.Low electron density is beneficial to reduce plasma frequency so that negative permittivity is achieved in kHz region.Negative permittivity achieved by percolating composites is restricted in practicality due to its instability nature at high temperatures.To achieve temperature-stable negative permittivity in kHz region,monophase La_(1-x)Ba_(x)CoO_(3)ceramics were prepared,and the transition from dielectric to metal was elaborated in the perspective of electrical conductivity and negative permittivity.The plasma-like negative permittivity is attained in kHz region,which is interpreted by the collective oscillation of low electron density.The temperature-stable negative permittivity is based on the fact that the plasmonic state will not be undermined at high temperatures.In addition,zero-crossing behavior of real permittivity is observed in La_(0.9)Ba_(0.1)CoO_(3)sample,which provides a promising alternative to designing epsilon-near-zero materials.This work makes the La_(1-x)Ba_(x)CoO_(3)system a source material for achieving effective negative permittivity.展开更多
Pb_(x)Sr_(1-x)TiO_(3)(x=0.30,0.35,0.40,0.45,0.50 and 0.55)ceramics were fabricated by a solid-state reaction route.Xeray diffraction data at room temperature show PST samples shift from cubic to tetragonal phase with ...Pb_(x)Sr_(1-x)TiO_(3)(x=0.30,0.35,0.40,0.45,0.50 and 0.55)ceramics were fabricated by a solid-state reaction route.Xeray diffraction data at room temperature show PST samples shift from cubic to tetragonal phase with the increase of Pb^(2+) content.The microstructures were observed by scanning electron microscopy.Dielectric measurement was employed to investigate the ferroelectriceparaelectric phase transition behavior.Temperature dependent polarizationeelectric field hysteresis loops were conducted to study the electrocaloric effect(ECE)of the ferroelectric ceramics by indirect methods over a wide temperature range.Direct measurement of temperature change(DT)at room temperature for all samples can achieve 0.79e1.86 K.What's more,a giant ECE(△T=2.05 K,EC strength(△T/△E)=0.51×10^(-6) K m/V,under 40 kV/cm)was obtained in the sample of x=0.35 near phase transition temperature.Our results suggest that the ceramics are promising cooling materials with excellent EC properties for energy related applications.展开更多
NASICON型快离子导体Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)(LATP)具有较高的离子电导率、较宽的电化学窗口及良好的水和空气稳定性,但其界面接触性能差。石榴石型Li_(7)La_(3)Zr_(2)O_(12)(LLZO)锂离子电导率高、电化学窗口较宽且热稳定...NASICON型快离子导体Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)(LATP)具有较高的离子电导率、较宽的电化学窗口及良好的水和空气稳定性,但其界面接触性能差。石榴石型Li_(7)La_(3)Zr_(2)O_(12)(LLZO)锂离子电导率高、电化学窗口较宽且热稳定性好,但其立方相结构不稳定,影响其实际应用。采用溶液浇筑法,制备纯PVDF-LiTFSI电解质膜和以PVDF为基、3种不同质量比的Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)的固态电解质膜,并探讨纯PVDF-LiTFSI电解质膜和3种不同质量比的活性无机电解质填料对复合固态电解质离子电导率的影响。结果表明,Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)质量比为1∶1时,电解质膜的XRD图谱的衍射峰比纯PVDF-LiTFSI下降更为明显,电化学窗口为3.9 V左右,表现出更好的稳定性。在不同温度下分别测量其离子电导率发现,Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)质量比为1∶1时的电解质膜均高于纯PVDF-LiTFSI电解质膜和Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)质量比为2∶1和3∶1时的电解质膜。将其装配成电池后发现,0.1C下电池首次充放电比容量分别为90 m A·h/g和87 m A·h/g。以0.5C的电流循环25圈,放电比容量从57 mA·h/g衰减至51mA·h/g,容量保持率为99.7%。所以,以PVDF为基、Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)质量比为1∶1的固态电解质膜有优良的倍率性能和循环稳定性能。展开更多
The study aims to investigate the structural and dielectric properties of perovskite La_(1-x)Sr_(x)FeO_(3)(x=0.1,0.2,0.3,and 0.4)synthesized by solgel and sintering methods.X-ray diffraction(XRD),transmission electron...The study aims to investigate the structural and dielectric properties of perovskite La_(1-x)Sr_(x)FeO_(3)(x=0.1,0.2,0.3,and 0.4)synthesized by solgel and sintering methods.X-ray diffraction(XRD),transmission electron microscopy(TEM),and LCR-Meter were used to identify the phase,crystallography parameters,morphology,particle size,and electrical behavior of the synthesized perovskite materials.The samples showed a single-phase orthorhombic crystal structure with Pbnm space group.Sr-substitution induced the volume unit cell and crystallite size to decrease.The synthesized nanoparticles were uniform and homogeneous with the particle size less than 200 nm.Impedance spectroscopy(IS)was used to explain the electrical behavior as a function of frequency(100 Hz to 1 MHz)at various temperatures(300–373 K).The presence of small polarons as charge carriers within the grain and grain boundary were elucidated from the electrical conductivity experiments.Sr-substitution caused the dielectric constant and electronic conductivity to increase with the highest values obtained from La_(1-x)Sr_(x)FeO_(3)(x=0.4).展开更多
The powders of lead-free material namely(nonhazardous)barium strontium titanate(BST)with different stoichiometric compo-sitions have been synthesized by the sol-gel method.Ba_(1−x)Sr_(x)TiO_(3)(BST)materials possess t...The powders of lead-free material namely(nonhazardous)barium strontium titanate(BST)with different stoichiometric compo-sitions have been synthesized by the sol-gel method.Ba_(1−x)Sr_(x)TiO_(3)(BST)materials possess the properties of both ferroelectric and dielectric materials.These materials have spontaneous polarization that can be reversed by an applied electric field and they remain polarized even when the applied external electric field is removed.Synthesized samples have been subjected to structural,morphological,and dielectric characterizations.In this study,BST nanopowders with different substitutions of x(where x=0.2,0.3,0.4,0.5,and 0.6)were prepared by the sol-gel method,which is an easy method with low power consumption and low tem-perature requirement and produces higher yield.Nanopowders had average particle sizes of 12-24 nm and particles sizes after sintering at 1000°C for 3 h were 197,267,79.80,63.09,and 63 nm.All resulting pellets had a polycrystalline structure.Crystal structure,space group,morphological characterization,and particle size were determined from the structural analysis using X-ray powder diffraction(XRD),energy-dispersive X-ray spectroscopy(EDX),and scanning electron microscopy(SEM).The dielec-tric measurements were made for BST pellets under different frequencies(1-200 kHz)from room temperature to 250℃.The dielectric constants for the bulk were 743,1566,1091,766,and 626 for x=0.2,0.3,0.4,0.5,and 0.6,respectively.From dielectric measurements,samples with x=0.2 and 0.3 had the Curie temperatures of 70℃ and 28.5℃,respectively,and remained intact below 0℃.The sample with x=0.3 had a good dielectric measurement and moderate dissipation factor;it may be used in capac-itance application as energy stores.展开更多
基金the National High-Tech Development Plan (2006AA05Z417)the Natural Science Foundation of Lia-oning Province (20062145)the Education department of Liaoning Province (05L073)
文摘The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitation method with metal-nitrates as starting materials and mixed alkali (NaOH and Na2CO3) as a precipitating agent. The formation process of LSCCF from the precursors was monitored by TG-DSC, and the crystal structure and particles morphology of the precursors which were calcined at 600, 800, 1000 ℃ for 3 h were characterized using XRD, SEM technologies. Compared with the solid state reaction of constituent oxides, when the pH value of the precipitating solution was in the range of 9.1～9.5, the LSCCF powders from the precursors caclined at 800 ℃ for 3 h had high purity, homogeneous and single perovskite phase. The electrical conductivity of the LSCCF samples sintered at 1200 ℃ for 3 h, which was measured as a function of temperatures from 100 to 800 ℃ by DC four-probe method in air, decreased with x from 0.05 to 0.20. The value of electrical conductivity was almost equal because of Ca2+, Sr2+ co-dopant resulting in the 'mix effect' while x=0.10 or 0.15. The electrical conductivity of all doped samples was higher than 100 S·cm-1 at intermediate temperatures from 500 to 800 ℃, and there was good compatibility between the LSCCF cathode and Ce0.8Sm0.2O2 electrolyte.
文摘With substitution of La by Tb in (La_(1-x)Tb_x)_(0.67)Sr_(0.33)MnO_3, the room temperature magnetoresistance △R/R_0drops at first, then undergoes an increase near x≈0.1, and finally drops again. The value of room temperaturemagnetoresistance at a field H=12 kOe for (La_(0.9)Tb_(0.1))_(0.67)Sr_(0.33)MnO_3 is -3.56%. The enhancement of the roomtemperature magnetoresistance induced by an appropriate Tb substitution in (La_(1-x)Tb_x)_(0.67)Sr_(0.33)MnO_3 is correlatedwith the shifts of the Curie temperature and metal-insulator temperature to near room temperature. The drop ofthe room temperature magnetoresistance at large Tb doping-contents may be due to its lower T_C and T_(MI) far fromthe room temperature.
基金This report is part of the fundamental research report with contract No.486 127/UN14.2/PNL.01.03.00/2016.
文摘In an effort to improve the performance of superconductors in the field and high temperatures it is important to study the superconducting mechanism. For this reason, the cation substitution can be conducted. One of the high Tc superconductors Gd1Ba2Cu3O7−δ phase with Sr substitution has been synthesized, i.e. Gd1(Ba2−xSrx)Cu3O7−δ compound. The sample was synthesized by using a solid-state reaction method with a wet mixing, sintered for 12 hours at temperature 900°C. The synthesis results are characterized by using XRD. The results of Match-3 software analysis showed high (higher 85%) Gd1Ba2Cu3O7−δ phase was formed. The Sr substitution causes changes to the structure, i.e. the lattice parameters a, b and c, where the orthorhombicity tends to decrease with increasing Sr content. Refinement results show that based on the oxygen occupancy, the total oxygen content tends to increase.
基金supported by the National Natural Science Foundation of China(Nos.51771104,51871146,51971119)the Natural Science Foundation of Shandong Province(No.ZR2020YQ32)the Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-10-E00053)。
文摘The development of negative permittivity materials in multifunctional applications requests expansion of their operating frequency and improvement of stability of negative permittivity.Low electron density is beneficial to reduce plasma frequency so that negative permittivity is achieved in kHz region.Negative permittivity achieved by percolating composites is restricted in practicality due to its instability nature at high temperatures.To achieve temperature-stable negative permittivity in kHz region,monophase La_(1-x)Ba_(x)CoO_(3)ceramics were prepared,and the transition from dielectric to metal was elaborated in the perspective of electrical conductivity and negative permittivity.The plasma-like negative permittivity is attained in kHz region,which is interpreted by the collective oscillation of low electron density.The temperature-stable negative permittivity is based on the fact that the plasmonic state will not be undermined at high temperatures.In addition,zero-crossing behavior of real permittivity is observed in La_(0.9)Ba_(0.1)CoO_(3)sample,which provides a promising alternative to designing epsilon-near-zero materials.This work makes the La_(1-x)Ba_(x)CoO_(3)system a source material for achieving effective negative permittivity.
基金the National Natural Science Foundation of China(Grant Nos.11574057 and 51604087)the Guangdong Provincial Natural Science Foundation of China(Grant No.2016A030313718)the Science and Technology Program of Guangdong Province of China(Grant Nos.2016A010104018,and 2017A010104022).
文摘Pb_(x)Sr_(1-x)TiO_(3)(x=0.30,0.35,0.40,0.45,0.50 and 0.55)ceramics were fabricated by a solid-state reaction route.Xeray diffraction data at room temperature show PST samples shift from cubic to tetragonal phase with the increase of Pb^(2+) content.The microstructures were observed by scanning electron microscopy.Dielectric measurement was employed to investigate the ferroelectriceparaelectric phase transition behavior.Temperature dependent polarizationeelectric field hysteresis loops were conducted to study the electrocaloric effect(ECE)of the ferroelectric ceramics by indirect methods over a wide temperature range.Direct measurement of temperature change(DT)at room temperature for all samples can achieve 0.79e1.86 K.What's more,a giant ECE(△T=2.05 K,EC strength(△T/△E)=0.51×10^(-6) K m/V,under 40 kV/cm)was obtained in the sample of x=0.35 near phase transition temperature.Our results suggest that the ceramics are promising cooling materials with excellent EC properties for energy related applications.
文摘NASICON型快离子导体Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)(LATP)具有较高的离子电导率、较宽的电化学窗口及良好的水和空气稳定性,但其界面接触性能差。石榴石型Li_(7)La_(3)Zr_(2)O_(12)(LLZO)锂离子电导率高、电化学窗口较宽且热稳定性好,但其立方相结构不稳定,影响其实际应用。采用溶液浇筑法,制备纯PVDF-LiTFSI电解质膜和以PVDF为基、3种不同质量比的Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)的固态电解质膜,并探讨纯PVDF-LiTFSI电解质膜和3种不同质量比的活性无机电解质填料对复合固态电解质离子电导率的影响。结果表明,Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)质量比为1∶1时,电解质膜的XRD图谱的衍射峰比纯PVDF-LiTFSI下降更为明显,电化学窗口为3.9 V左右,表现出更好的稳定性。在不同温度下分别测量其离子电导率发现,Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)质量比为1∶1时的电解质膜均高于纯PVDF-LiTFSI电解质膜和Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)质量比为2∶1和3∶1时的电解质膜。将其装配成电池后发现,0.1C下电池首次充放电比容量分别为90 m A·h/g和87 m A·h/g。以0.5C的电流循环25圈,放电比容量从57 mA·h/g衰减至51mA·h/g,容量保持率为99.7%。所以,以PVDF为基、Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)和Li_(1+x)Al_(x)Ti_(2-x)(PO_(4))_(3)质量比为1∶1的固态电解质膜有优良的倍率性能和循环稳定性能。
基金Ministry of TechnologyResearch and Higher Education of Republic of Indonesiaunder KLN Grant No. 537/UN2.R3.1/HKP05.00/2018.
文摘The study aims to investigate the structural and dielectric properties of perovskite La_(1-x)Sr_(x)FeO_(3)(x=0.1,0.2,0.3,and 0.4)synthesized by solgel and sintering methods.X-ray diffraction(XRD),transmission electron microscopy(TEM),and LCR-Meter were used to identify the phase,crystallography parameters,morphology,particle size,and electrical behavior of the synthesized perovskite materials.The samples showed a single-phase orthorhombic crystal structure with Pbnm space group.Sr-substitution induced the volume unit cell and crystallite size to decrease.The synthesized nanoparticles were uniform and homogeneous with the particle size less than 200 nm.Impedance spectroscopy(IS)was used to explain the electrical behavior as a function of frequency(100 Hz to 1 MHz)at various temperatures(300–373 K).The presence of small polarons as charge carriers within the grain and grain boundary were elucidated from the electrical conductivity experiments.Sr-substitution caused the dielectric constant and electronic conductivity to increase with the highest values obtained from La_(1-x)Sr_(x)FeO_(3)(x=0.4).
文摘The powders of lead-free material namely(nonhazardous)barium strontium titanate(BST)with different stoichiometric compo-sitions have been synthesized by the sol-gel method.Ba_(1−x)Sr_(x)TiO_(3)(BST)materials possess the properties of both ferroelectric and dielectric materials.These materials have spontaneous polarization that can be reversed by an applied electric field and they remain polarized even when the applied external electric field is removed.Synthesized samples have been subjected to structural,morphological,and dielectric characterizations.In this study,BST nanopowders with different substitutions of x(where x=0.2,0.3,0.4,0.5,and 0.6)were prepared by the sol-gel method,which is an easy method with low power consumption and low tem-perature requirement and produces higher yield.Nanopowders had average particle sizes of 12-24 nm and particles sizes after sintering at 1000°C for 3 h were 197,267,79.80,63.09,and 63 nm.All resulting pellets had a polycrystalline structure.Crystal structure,space group,morphological characterization,and particle size were determined from the structural analysis using X-ray powder diffraction(XRD),energy-dispersive X-ray spectroscopy(EDX),and scanning electron microscopy(SEM).The dielec-tric measurements were made for BST pellets under different frequencies(1-200 kHz)from room temperature to 250℃.The dielectric constants for the bulk were 743,1566,1091,766,and 626 for x=0.2,0.3,0.4,0.5,and 0.6,respectively.From dielectric measurements,samples with x=0.2 and 0.3 had the Curie temperatures of 70℃ and 28.5℃,respectively,and remained intact below 0℃.The sample with x=0.3 had a good dielectric measurement and moderate dissipation factor;it may be used in capac-itance application as energy stores.
