Perovskite type of PbTiO 3 fine powders which are homogeneous in physic chemical properties has been hydrothermally synthesized from the different precursors. The borderline reaction conditions, such as temperature...Perovskite type of PbTiO 3 fine powders which are homogeneous in physic chemical properties has been hydrothermally synthesized from the different precursors. The borderline reaction conditions, such as temperature and time, for the formation of PbTiO 3 were established and the effect of the precursor on the particle properties was investigated. As a precursor, Pb Ti alko carbonate xerogel dispersed in 2 methoxyethanol was found to be effective for the synthesis of the PbTiO 3 powders with a lower agglomeration and a simple mode of particle size.展开更多
The single-phase Ba(Mg_(1/3)Nb_(2/3))O_3(BMN) powder was successfully prepared by the KCl molten salt synthesis(MSS) method.The temperature for single-phase BMN powders by MSS was about 400℃ lower than that by the so...The single-phase Ba(Mg_(1/3)Nb_(2/3))O_3(BMN) powder was successfully prepared by the KCl molten salt synthesis(MSS) method.The temperature for single-phase BMN powders by MSS was about 400℃ lower than that by the solid-phase method.The average particle size(APS) was about 0.91μm at 900℃ and increased with increasing synthesis temperature.Based on the APS,the activation energy for particle growth in the MSS,whose value was 64.1kJmol^(-1),was attained.The sinterability of the powder prepared by MSS method was better than that prepared by solid-phase method.展开更多
A nitrate-citrate combustion route to synthesize La0.9Sr0.1Ga0.8Mg0.2O3-σ powder for solid oxide fuel cell application was presented. This route is based on the gelling of nitrate solutions by the addition of citric ...A nitrate-citrate combustion route to synthesize La0.9Sr0.1Ga0.8Mg0.2O3-σ powder for solid oxide fuel cell application was presented. This route is based on the gelling of nitrate solutions by the addition of citric acid and ammonium hydroxide, followed by an intense combustion process due to an exothermic redox reaction between nitrate and citrate ions. The optimum technical parameters are that the pH value is 5, and the molar ratio of citric acid to the total metallic ion is 1.5:1. X-ray diffraction characterization of calcined gel shows that pure phase was synthesized after calcination at 1400℃for 10 h, and the TEM result shovvs the calcined powder with average particle size is about 150 nm. The grain resistance contributes to the total resistance of sintered peliet below 500℃. The conductivity of the sintered peliet at 800℃ was 0.07 S-1·cm-1 higher than the conductivity of YSZ (0.05 S-1·cm-1 at 800℃)展开更多
Nanosized BaCe_(0.95)Y_(0.05)O_(3-δ) powders with the homogeneous composition were synthesized by a new combustion process based on the Pechini method. A polymeric precursor sol was formed by use of citric acid and e...Nanosized BaCe_(0.95)Y_(0.05)O_(3-δ) powders with the homogeneous composition were synthesized by a new combustion process based on the Pechini method. A polymeric precursor sol was formed by use of citric acid and ethylene glycol as the chelating agents of metal ions. The perovskite-type BaCe_(0.95)Y_(0.05)O_(3-δ) powders with uniform shape and smaller than 40 nm in sized were obtained through the combustion of the polymeric precursor sol at the existence of nitric acid and ammonium hydroxide. It was found the particle size could be controlled by modulating the quantities of nitric acid and ammonium hydroxide, the quantities of the residue, carbonate ions were also affected by the quantities of the citric acid and ethylene glycol.展开更多
The NaNbO3 powders were synthesized and their crystal structure changes were analyzed by ultrahigh pressure up to 6 GPa.The results indicate that the pure NaNbO3 powders can be synthesized at 300℃ under a pressure of...The NaNbO3 powders were synthesized and their crystal structure changes were analyzed by ultrahigh pressure up to 6 GPa.The results indicate that the pure NaNbO3 powders can be synthesized at 300℃ under a pressure of 4 GPa, to sig- nificantly restrain the Na element volatilization compared with the traditional syn- thesis method. It is found that the crystal structure of synthesized NaNbO3 changes from low symmetry to high symmetry with the increase of the pressure.展开更多
Spherical Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 was prepared via the homogenous precursors produced by solution spray-drying method. The precursors were sintered at different temperatures between 600 and 1 000 ℃ for 10 h. ...Spherical Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 was prepared via the homogenous precursors produced by solution spray-drying method. The precursors were sintered at different temperatures between 600 and 1 000 ℃ for 10 h. The impacts of different sintering temperatures on the structure and electrochemical performances of Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 were compared by means of X-ray diffractometry(XRD), scanning electron microscopy(SEM), and charge/discharge test as cathode materials for lithium ion batteries. The experimental results show that the spherical morphology of the spray-dried powers maintains during the subsequent heat treatment and the specific capacity increases with rising sintering temperature. When the sintering temperature rises up to 900 ℃ , Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 attains a reversible capacity of 153 mA·h/g between 3.00 and 4.35 V at 0.2C rate with excellent cyclability.展开更多
Low temperature direct synthesis (LTDS) involves the preparation of a base solution of Sr^(2+),and the mixing of base solution with tetrabutyl titanate solution.LTDS is an advantageous method because it does not requi...Low temperature direct synthesis (LTDS) involves the preparation of a base solution of Sr^(2+),and the mixing of base solution with tetrabutyl titanate solution.LTDS is an advantageous method because it does not require the complex hydrothermal facilities and it can prevent the agglomeration in calcinations of other liquid methods.In our work,we adopted LTDS method to prepare the nano strontium titanate powders,and characterize them by XRD,FT-IR and TGA.The influences of preparation temperature and solvents on grain size and lattice parameters were investigated.The results show that preparation temperature can slightly change the lattice parameters of grain,while solvents also play important roles in the preparation.展开更多
Three-dimensional hierarchical structure coral-like BaTiO3 nanoparticles have been self-assembled by a facile one step hydrothermal method. Cetyltrimethyl ammonium bromide(CTAB),Ba(OH)2·8H2O and tetrabutyl titana...Three-dimensional hierarchical structure coral-like BaTiO3 nanoparticles have been self-assembled by a facile one step hydrothermal method. Cetyltrimethyl ammonium bromide(CTAB),Ba(OH)2·8H2O and tetrabutyl titanate have been used as precursors. The prepared Ba TiO3 exhibits cubic perovskite phase at room temperature,and the coral-like architecture is a micro-nano hiberarchy consisted of dendrimer-like structure and trunk-like structure. By adjusting the hydrothermal duration and the precursor substances,a surfactant induced mechanism is proposed to understand the self-assembly process. UV-vis measurement demonstrates that the as-prepared Ba TiO3 nanoparticles exhibit dozens of times overwhelming absorptive character compared to the ordinary nanospheres at ultraviolet band,which is benefited from the coral-like porous framework. Moreover,halogen anions( F,Cl,Br,and I) have been chosen to adjust the coral-like Ba TiO3 physical properties. Results show the halogen doping produces distinct modulation effect on the grain size,UV-vis absorbance and photoluminescence properties of the materials. The coral-like BaTiO3 nanoparticle and its halogen modified ramifications offer significant opportunities to develop nano-laser devices,photon detectors,photocatalyst based on BaTiO3 perovskite materials.展开更多
A series of Ba1-xSrxTi1-yZryO3 (0≤x≤0.5, 0≤y≤0.4) and Ba1-xZnxTi1-ySnyO3 (0≤x≤0.3, 0≤y≤0.3) solid solutions were synthesized by low-temperature/low-pressure hydrothermal method below 170℃, 0.8 MPa. XRD patter...A series of Ba1-xSrxTi1-yZryO3 (0≤x≤0.5, 0≤y≤0.4) and Ba1-xZnxTi1-ySnyO3 (0≤x≤0.3, 0≤y≤0.3) solid solutions were synthesized by low-temperature/low-pressure hydrothermal method below 170℃, 0.8 MPa. XRD pattern and cell parameters-composition figures of these prepared powders demonstrated that they are completely miscible solid solutions based on BaTiO3. Furthermore, TEM showed that they have a shape of uniform, substantially spherical particles with an average particle size of 70 nm in diameter. The sintered ceramics of those powders doped by Sr2+ and Zr4+ or Zn2+ and Sn4+ have dielectric constant twelve times higher than and dielectric loss 1/6 those of pure BaTiO3 phase at room temperature.展开更多
White light-emitting YVO4:1 mol.%Dy3+,x mol.%Eu3+ phosphor powders with order morphology and well crystallization were hydrothermally synthesized at 180°C. The microstructure, white-light emission, and light-emit...White light-emitting YVO4:1 mol.%Dy3+,x mol.%Eu3+ phosphor powders with order morphology and well crystallization were hydrothermally synthesized at 180°C. The microstructure, white-light emission, and light-emitting mechanism of the powders were carefully studied using X-ray diffractometry, scanning electron microscopy and photoluminescence spectra. The excitation and emission spectra of the phosphor powders indicated the coexistence of efficient energy transfer from Eu3+ to Dy3+ and inefficient en-ergy transfer from Dy3+ to Eu3+ besides the energy transfer from VO43– to Eu3+. Increasing the Eu3+ concentration initially enhanced and then weakened the luminescent intensity of Dy3+. The white-light emissions of YVO4:1 mol.%Dy3+,xmol.%Eu3+ phosphor pow-ders were both related to the energy transfer between VO43– and Dy3+/Eu3+, as well as between Eu3+ and Dy3+. The inefficient energy transfer from Dy3+ to Eu3+ was first found.展开更多
本文用化学共沉淀法制备 Ba Ti O3超细粉 ,实验中分别采用氢氧化钠和草酸作沉淀剂。实验发现 ,采用不同的沉淀剂均能制出具有四方晶相的 Ba Ti O3粉体 ,但其所含微量成分有所不同 ,粉体粒度分布有较大差别。通过对粉体进行半导化处理 ,...本文用化学共沉淀法制备 Ba Ti O3超细粉 ,实验中分别采用氢氧化钠和草酸作沉淀剂。实验发现 ,采用不同的沉淀剂均能制出具有四方晶相的 Ba Ti O3粉体 ,但其所含微量成分有所不同 ,粉体粒度分布有较大差别。通过对粉体进行半导化处理 ,发现用氢氧化钠作沉淀剂时不易半导化 ,且其烧结性能及机械性能较差 ,而用草酸作沉淀剂所得的粉体易半导化 ,且具有较好的烧结性能和机械性能。展开更多
The size of BaTiO3 particles was controlled by adjusting the molar ratio of the starting materials (BaCl2 + TiO2) to mineralizer (NaOH + KOH) during a composite-hydroxide-mediated approach using a novel hydrothermal r...The size of BaTiO3 particles was controlled by adjusting the molar ratio of the starting materials (BaCl2 + TiO2) to mineralizer (NaOH + KOH) during a composite-hydroxide-mediated approach using a novel hydrothermal reaction apparatus with a rolling system. The mean particle diameter decreased from 500 to 50 nm with a decrease in the (BaCl2 + TiO2)/(NaOH + KOH) molar ratio from 0.44 to 0.04. The powders were sintered by normal one-step sintering at 1200°C for 5 h and two-step sintering in which temperature was raised to 1200°C at first and then decreased to 1100°C and kept at 1100°C for 5 h. The BaTiO3 particles prepared with the (BaCl2 + TiO2)/(NaOH + KOH) molar ratio of 0.32 and 0.22 showed excellent sinterability and could be sintered to almost full theoretical density by both method. The sintered bodies obtained by both methods showed similarly excellent dielectric and piezoelectric properties.展开更多
文摘Perovskite type of PbTiO 3 fine powders which are homogeneous in physic chemical properties has been hydrothermally synthesized from the different precursors. The borderline reaction conditions, such as temperature and time, for the formation of PbTiO 3 were established and the effect of the precursor on the particle properties was investigated. As a precursor, Pb Ti alko carbonate xerogel dispersed in 2 methoxyethanol was found to be effective for the synthesis of the PbTiO 3 powders with a lower agglomeration and a simple mode of particle size.
基金FinanciallysupportedbytheMinistryofEducationofChi na .
文摘The single-phase Ba(Mg_(1/3)Nb_(2/3))O_3(BMN) powder was successfully prepared by the KCl molten salt synthesis(MSS) method.The temperature for single-phase BMN powders by MSS was about 400℃ lower than that by the solid-phase method.The average particle size(APS) was about 0.91μm at 900℃ and increased with increasing synthesis temperature.Based on the APS,the activation energy for particle growth in the MSS,whose value was 64.1kJmol^(-1),was attained.The sinterability of the powder prepared by MSS method was better than that prepared by solid-phase method.
基金The authors acknowledge financial support from 863 National Project(No.2003AA302440).
文摘A nitrate-citrate combustion route to synthesize La0.9Sr0.1Ga0.8Mg0.2O3-σ powder for solid oxide fuel cell application was presented. This route is based on the gelling of nitrate solutions by the addition of citric acid and ammonium hydroxide, followed by an intense combustion process due to an exothermic redox reaction between nitrate and citrate ions. The optimum technical parameters are that the pH value is 5, and the molar ratio of citric acid to the total metallic ion is 1.5:1. X-ray diffraction characterization of calcined gel shows that pure phase was synthesized after calcination at 1400℃for 10 h, and the TEM result shovvs the calcined powder with average particle size is about 150 nm. The grain resistance contributes to the total resistance of sintered peliet below 500℃. The conductivity of the sintered peliet at 800℃ was 0.07 S-1·cm-1 higher than the conductivity of YSZ (0.05 S-1·cm-1 at 800℃)
文摘Nanosized BaCe_(0.95)Y_(0.05)O_(3-δ) powders with the homogeneous composition were synthesized by a new combustion process based on the Pechini method. A polymeric precursor sol was formed by use of citric acid and ethylene glycol as the chelating agents of metal ions. The perovskite-type BaCe_(0.95)Y_(0.05)O_(3-δ) powders with uniform shape and smaller than 40 nm in sized were obtained through the combustion of the polymeric precursor sol at the existence of nitric acid and ammonium hydroxide. It was found the particle size could be controlled by modulating the quantities of nitric acid and ammonium hydroxide, the quantities of the residue, carbonate ions were also affected by the quantities of the citric acid and ethylene glycol.
基金Supported by the National Natural Science Foundation of China (Grant No. 50502027)the Chenguang Science Plan of Wuhan (Grant No. 200750731268)
文摘The NaNbO3 powders were synthesized and their crystal structure changes were analyzed by ultrahigh pressure up to 6 GPa.The results indicate that the pure NaNbO3 powders can be synthesized at 300℃ under a pressure of 4 GPa, to sig- nificantly restrain the Na element volatilization compared with the traditional syn- thesis method. It is found that the crystal structure of synthesized NaNbO3 changes from low symmetry to high symmetry with the increase of the pressure.
文摘Spherical Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 was prepared via the homogenous precursors produced by solution spray-drying method. The precursors were sintered at different temperatures between 600 and 1 000 ℃ for 10 h. The impacts of different sintering temperatures on the structure and electrochemical performances of Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 were compared by means of X-ray diffractometry(XRD), scanning electron microscopy(SEM), and charge/discharge test as cathode materials for lithium ion batteries. The experimental results show that the spherical morphology of the spray-dried powers maintains during the subsequent heat treatment and the specific capacity increases with rising sintering temperature. When the sintering temperature rises up to 900 ℃ , Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 attains a reversible capacity of 153 mA·h/g between 3.00 and 4.35 V at 0.2C rate with excellent cyclability.
基金support from Jiangxi Education Science FoundationNanchang University Science Foundation.
文摘Low temperature direct synthesis (LTDS) involves the preparation of a base solution of Sr^(2+),and the mixing of base solution with tetrabutyl titanate solution.LTDS is an advantageous method because it does not require the complex hydrothermal facilities and it can prevent the agglomeration in calcinations of other liquid methods.In our work,we adopted LTDS method to prepare the nano strontium titanate powders,and characterize them by XRD,FT-IR and TGA.The influences of preparation temperature and solvents on grain size and lattice parameters were investigated.The results show that preparation temperature can slightly change the lattice parameters of grain,while solvents also play important roles in the preparation.
基金financially supported by the One Hundred Talents Project Foundation Program (1029271301)the Western Light Talent Culture Project (Grant No.RCPY201206) of Chinese Academy of Sciences+1 种基金the National Natural Science Foundation of China (Grant Nos.41302029 and 41130746)the International Technology Cooperation Foundation of Autonomous Region (20136009)
文摘Three-dimensional hierarchical structure coral-like BaTiO3 nanoparticles have been self-assembled by a facile one step hydrothermal method. Cetyltrimethyl ammonium bromide(CTAB),Ba(OH)2·8H2O and tetrabutyl titanate have been used as precursors. The prepared Ba TiO3 exhibits cubic perovskite phase at room temperature,and the coral-like architecture is a micro-nano hiberarchy consisted of dendrimer-like structure and trunk-like structure. By adjusting the hydrothermal duration and the precursor substances,a surfactant induced mechanism is proposed to understand the self-assembly process. UV-vis measurement demonstrates that the as-prepared Ba TiO3 nanoparticles exhibit dozens of times overwhelming absorptive character compared to the ordinary nanospheres at ultraviolet band,which is benefited from the coral-like porous framework. Moreover,halogen anions( F,Cl,Br,and I) have been chosen to adjust the coral-like Ba TiO3 physical properties. Results show the halogen doping produces distinct modulation effect on the grain size,UV-vis absorbance and photoluminescence properties of the materials. The coral-like BaTiO3 nanoparticle and its halogen modified ramifications offer significant opportunities to develop nano-laser devices,photon detectors,photocatalyst based on BaTiO3 perovskite materials.
基金the Natural Science Foundation of Hebei Province, China (Grant No. 299078).
文摘A series of Ba1-xSrxTi1-yZryO3 (0≤x≤0.5, 0≤y≤0.4) and Ba1-xZnxTi1-ySnyO3 (0≤x≤0.3, 0≤y≤0.3) solid solutions were synthesized by low-temperature/low-pressure hydrothermal method below 170℃, 0.8 MPa. XRD pattern and cell parameters-composition figures of these prepared powders demonstrated that they are completely miscible solid solutions based on BaTiO3. Furthermore, TEM showed that they have a shape of uniform, substantially spherical particles with an average particle size of 70 nm in diameter. The sintered ceramics of those powders doped by Sr2+ and Zr4+ or Zn2+ and Sn4+ have dielectric constant twelve times higher than and dielectric loss 1/6 those of pure BaTiO3 phase at room temperature.
基金supported by the National Natural Science Foundation of China(60807001)the Foundation of Young Key Teachers from Universities of Henan Province(2011GGJS-008)the Foundation of Henan Educational Committee(2010A140017)
文摘White light-emitting YVO4:1 mol.%Dy3+,x mol.%Eu3+ phosphor powders with order morphology and well crystallization were hydrothermally synthesized at 180°C. The microstructure, white-light emission, and light-emitting mechanism of the powders were carefully studied using X-ray diffractometry, scanning electron microscopy and photoluminescence spectra. The excitation and emission spectra of the phosphor powders indicated the coexistence of efficient energy transfer from Eu3+ to Dy3+ and inefficient en-ergy transfer from Dy3+ to Eu3+ besides the energy transfer from VO43– to Eu3+. Increasing the Eu3+ concentration initially enhanced and then weakened the luminescent intensity of Dy3+. The white-light emissions of YVO4:1 mol.%Dy3+,xmol.%Eu3+ phosphor pow-ders were both related to the energy transfer between VO43– and Dy3+/Eu3+, as well as between Eu3+ and Dy3+. The inefficient energy transfer from Dy3+ to Eu3+ was first found.
文摘本文用化学共沉淀法制备 Ba Ti O3超细粉 ,实验中分别采用氢氧化钠和草酸作沉淀剂。实验发现 ,采用不同的沉淀剂均能制出具有四方晶相的 Ba Ti O3粉体 ,但其所含微量成分有所不同 ,粉体粒度分布有较大差别。通过对粉体进行半导化处理 ,发现用氢氧化钠作沉淀剂时不易半导化 ,且其烧结性能及机械性能较差 ,而用草酸作沉淀剂所得的粉体易半导化 ,且具有较好的烧结性能和机械性能。
文摘The size of BaTiO3 particles was controlled by adjusting the molar ratio of the starting materials (BaCl2 + TiO2) to mineralizer (NaOH + KOH) during a composite-hydroxide-mediated approach using a novel hydrothermal reaction apparatus with a rolling system. The mean particle diameter decreased from 500 to 50 nm with a decrease in the (BaCl2 + TiO2)/(NaOH + KOH) molar ratio from 0.44 to 0.04. The powders were sintered by normal one-step sintering at 1200°C for 5 h and two-step sintering in which temperature was raised to 1200°C at first and then decreased to 1100°C and kept at 1100°C for 5 h. The BaTiO3 particles prepared with the (BaCl2 + TiO2)/(NaOH + KOH) molar ratio of 0.32 and 0.22 showed excellent sinterability and could be sintered to almost full theoretical density by both method. The sintered bodies obtained by both methods showed similarly excellent dielectric and piezoelectric properties.
