Bi-based perovskite ferroelectric thin films have wide applications in electronic devices due to their excellent ferroelectric properties.New Bi-based perovskite thin films Bi(Cu_(1/2)Ti_(1/2))O_(3)–PbTiO_(3)(BCT–PT...Bi-based perovskite ferroelectric thin films have wide applications in electronic devices due to their excellent ferroelectric properties.New Bi-based perovskite thin films Bi(Cu_(1/2)Ti_(1/2))O_(3)–PbTiO_(3)(BCT–PT) are deposited on Pt(111)/Ti/SiO_(2)/Si substrates in the present study by the traditional sol–gel method.Their structures and related ferroelectric and fatigue characteristics are studied in-depth.The BCT–PT thin films exhibit good crystallization within the phase-pure perovskite structure,besides,they have a predominant(100) orientation together with a dense and homogeneous microstructure.The remnant polarization(2P_(r)) values at 30 μC/cm^(2) and 16 μC/cm^(2) are observed in 0.1BCT–0.9PT and 0.2BCT–0.8PT thin films,respectively.More intriguingly,although the polarization values are not so high,0.2BCT–0.8PT thin films show outstanding polarization fatigue properties,with a high switchable polarization of 93.6% of the starting values after 10^(8) cycles,indicating promising applications in ferroelectric memories.展开更多
Pb(Mg_(1/3)Nb_(2/3))O_(3)–PbTiO_(3)(PMN-PT)piezoelectric ceramics have excellent piezoelectric properties and are used in a wide range of applications.Adjusting the solid solution ratios of PMN/PT and different conce...Pb(Mg_(1/3)Nb_(2/3))O_(3)–PbTiO_(3)(PMN-PT)piezoelectric ceramics have excellent piezoelectric properties and are used in a wide range of applications.Adjusting the solid solution ratios of PMN/PT and different concentrations of elemental doping are the main methods to modulate their piezoelectric coefficients.The combination of these controllable conditions leads to an exponential increase of possible compositions in ceramics,which makes it not easy to extend the sample data by additional experimental or theoretical calculations.In this paper,a physics-embedded machine learning method is proposed to overcome the difficulties in obtaining piezoelectric coefficients and Curie temperatures of Sm-doped PMN-PT ceramics with different components.In contrast to all-data-driven model,physics-embedded machine learning is able to learn nonlinear variation rules based on small datasets through potential correlation between ferroelectric properties.Based on the model outputs,the positions of morphotropic phase boundary(MPB)with different Sm doping amounts are explored.We also find the components with the best piezoelectric property and comprehensive performance.Moreover,we set up a database according to the obtained results,through which we can quickly find the optimal components of Sm-doped PMN-PT ceramics according to our specific needs.展开更多
Nanocrystalline rare earth mixed oxides SmFe_(1-x)Co_xO_(3-delta) wereprepared by sol-gel method at 1 073 K for 2 h calcination and characterized by X-ray diffraction(XRD) and scanning electron microscope (SEM). The r...Nanocrystalline rare earth mixed oxides SmFe_(1-x)Co_xO_(3-delta) wereprepared by sol-gel method at 1 073 K for 2 h calcination and characterized by X-ray diffraction(XRD) and scanning electron microscope (SEM). The results show that SmFe_(1-x)Co_xO_(3-delta) hasthe structure of perovskite type. The conductivity of the materials increases with the temperaturerising and the maximum conductivity at 1 073 K is 2.6 S/cm with the best mole ratio of Fe^(3+) toCo^(3+) being 1: 4. This kind of oxide is a conductive ceramic material by means of conduction ofelectron and oxygen anion.展开更多
Quantum chemistry calculations of La , Ca modified and pure PbTiO\-3 nanocrystals were carried out by means of the cluster model in DFT DVM calculating program on which the regularity of the charge distribution was...Quantum chemistry calculations of La , Ca modified and pure PbTiO\-3 nanocrystals were carried out by means of the cluster model in DFT DVM calculating program on which the regularity of the charge distribution was drawn. The analysis of the density of state(DOS) showed that when the cubic phase PbTiO 3 nanocrystal is changed into tetragonal phase, the interaction among Ti 3d , O 2p , and Pb 6p atomic orbitals causes the dipole moment and spontaneous polarization on the axis of the crystal, which resulted in the appearance of ferroelectric phase. At the same time, the dipole moment and the intensity of the spontaneous polarization were calculated as well.展开更多
Nanocrystalline TiO2 was prepared by high frequency plasma chemical vapor deposition (HF-PCVD). The effects of additive AlCl3 on crystal phase, particle size and microstructurai parameters of TiO2 nanocrystallites wer...Nanocrystalline TiO2 was prepared by high frequency plasma chemical vapor deposition (HF-PCVD). The effects of additive AlCl3 on crystal phase, particle size and microstructurai parameters of TiO2 nanocrystallites were investigated by X-ray diffraction(XRD) and transmission electron microscopy (TEM). The nanocrystallites obtained experimentally are mixture of anatase and rutile, the uniform diameters of particles are about 30 nm. The phase transformation from anatase to rutile was accelerated by AlCl3, and rutile content is increased from 26.7 wt pct to 53.6 wt pct with increasing of addition of AlCl3 from 0.0 wt pct to 5.0 wt pct. The particle size is reduced and the size distribution becomes very narrow. The crystal lattice constants have the trend to decrease, and celi volumes appear as shrinkable.展开更多
Nanocrystalline monoclinic and cubic Gd 2O 3∶Eu with different Eu 3+ concentration were prepared using glycine-nitrate combustion synthesis. By changing the ratio of glycine to nitrate and proper heat treatment, p...Nanocrystalline monoclinic and cubic Gd 2O 3∶Eu with different Eu 3+ concentration were prepared using glycine-nitrate combustion synthesis. By changing the ratio of glycine to nitrate and proper heat treatment, pure monoclinic and cubic Gd 2O 3∶Eu with particle size less than 40 nm can be easily formed. Under ultraviolet excitation, main emission of Eu 3+ ( 5D 0→ 7F 2) locates at 624 nm in monoclinic Gd 2O 3∶Eu and 611 nm in cubic sample. In excitation spectrum two broad bands corresponding to the host absorption and charge transfer state (CTS) and f-f transitions of Gd 3+ and Eu 3+ were observed and discussed. The quenching concentration of monoclinic and cubic Gd 2O 3∶Eu is 10% and 15%, respectively, both of which are much higher than that of bulk Gd 2O 3∶Eu.展开更多
The gaseous Pr-penetration is a new method to modify ceramics, which is expected to be a promising method for producing new conductor ceramic materials. The gaseous penetration of Pr into PbTiO_3 ceramics and their im...The gaseous Pr-penetration is a new method to modify ceramics, which is expected to be a promising method for producing new conductor ceramic materials. The gaseous penetration of Pr into PbTiO_3 ceramics and their improved electric properties were reported. Through XRD, EPMA and SEM analysis,it is confirmed that the gaseous penetration makes Pr enter into PbTiO_3 ceramics, and the new compound of Pr_2Ti_2O_7 is formed by the penetration of Pr in the gaseous state. The formed new Pr_2Ti_2O_7-PbTiO_3 ceramic materials have a significant change in electric properties. The room temperature resistivity decreases from 2.0×10^(10) Ω·m to 9.487 Ω·m. The grain resistance and the grain boundary resistance decrease with increase in temperature, and the PTCR effect disappears. The tendency of transition to a conductive body is manifest.展开更多
The rods that were shaped from nanocrystalline WC- 10.21 Co-0.42 VC/ Cr3 C2 （ wt% ） composite powders by using powder extrusion molding （PEM） were investigated. The nanocrystalline WC- 10.21 Co- 0. 42 VC/ Cr3 C2 ...The rods that were shaped from nanocrystalline WC- 10.21 Co-0.42 VC/ Cr3 C2 （ wt% ） composite powders by using powder extrusion molding （PEM） were investigated. The nanocrystalline WC- 10.21 Co- 0. 42 VC/ Cr3 C2 （ wt% ） composite powders were prepared by the spray thermal decomposition-continuous reduction and carburization technology. In order to improve the properties of rods shaped by using powder extrusion molding, the cold isostatic pressing （CIP） technology was used before or after debinding. Specimens were siutered by vacuum siutering and hot isostatic pressing （HIP）. The density, Rockwell A hardness, magnetic coercivity , and magnetic saturation induction of siutered specimen were measured. The microstructure of the green bodies and the siutered specimens was studied by scanning electron microscopy （SEM）. Results show that the rod formed by using powder extrusion molding after debinding and followed by cold isostatic pressing can be siutered to 99.5% density of composite cemented carbide rods with an average grain size of about 200- 300 nm, magnetic coercivity of 30.4 KA / m, Rockwell A hardness of 92.6 and magnetic saturation induction of 85% . Superfine WC- 10 Co cemented carbide rods with excellent properties were obtained.展开更多
Alumina (Al2O3) has been synthesized through combustion synthesis (CS) technique. The calcined products were characterized using X-ray diffractional analysis (XRD), scanning electron microscopy (SEM), transmission ele...Alumina (Al2O3) has been synthesized through combustion synthesis (CS) technique. The calcined products were characterized using X-ray diffractional analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermo-gravimetric analysis (TGA). TG-DTA results reveal the various stages involved in transition from γ-phase to α-Al2O3 phase. The first phase γ-Al2O3 was presented in the temperature range from 600°C-875°C as deduced from the XRD patterns with cubic crystal structure. The second stage occurs in the temperature range from 900°C-1000°C. In the final step, above 1000°C, the aluminium oxide appears completely as α-Al2O3, showing high crystallinity. The particle sizes are closely related to γ- to α-Al2O3 phase transition.展开更多
Nanocrystalline rare earth mixed oxides DyFe x Co 1- x O 3- δ were prepared by sol gel method and characterized by X ray diffraction (XRD), thermogravimetric analysis (TG DTA) and scanning elec...Nanocrystalline rare earth mixed oxides DyFe x Co 1- x O 3- δ were prepared by sol gel method and characterized by X ray diffraction (XRD), thermogravimetric analysis (TG DTA) and scanning electron microscope (SEM). The results show that DyFe x Co 1- x O 3- δ has the structure of perovskite type at 800 ℃ for 2 h calcination. The conductivity of the materials at different temperature was measured by four probe instrumentation and two pole method. The results show that the conductivity of mixed oxides DyFe x Co 1- x O 3- δ is higher than those of un mixed oxides DyFeO 3 and DyCoO 3 and the conductivity is the best at x =0.8 in the matter of DyFe x Co 1- x O 3- δ . The conductivity of these materials always increases with the temperature rising and there is an apparent change between 600 and 800 ℃. However, the spinodals are different with different ration of Fe 3+ and Co 3+ . This kind of oxide is a conductive pottery material.展开更多
La2O3 and Ce2O3 were penetrated into PbTiO3 to obtain conductive powders, and then they were mixed with polyurethane and butyl acetate to prepare conductive coatings. The results showed that the electric property of m...La2O3 and Ce2O3 were penetrated into PbTiO3 to obtain conductive powders, and then they were mixed with polyurethane and butyl acetate to prepare conductive coatings. The results showed that the electric property of modified PbTiO3 powders was improved by penetration of La2O3 and Ce2O3. XRD patterns showed that some new compounds such as La2Ti6O15, CeTi21O38 and Pb0.634La0.209Ti0.948O2.284 were formed, which led to the rapid increase of conductivity. The resistivity of modified PbTiO3 powders decreased to 3.88 Ω·m. The coatings using modified PbTiO3 powders as fillings also had a good conductivity. When the PbTiO3 powders were 10% and antisettle agent (bentonite) content was 0.50%, and mass ratio between polyurethane and butyl acetate was 1.05, the surface resistivity of the coatings fell down to 1.3×108 Ω·m. This kind of conductive coatings could be used in electromagnetic shielding.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFA1400300)the National Natural Science Foundation of China(Grant Nos.22271309,21805215,11934017,12261131499,and 11921004)+1 种基金the Beijing Natural Science Foundation(Grant No.Z200007)the Fund from the Chinese Academy of Sciences(Grant No.XDB33000000)。
文摘Bi-based perovskite ferroelectric thin films have wide applications in electronic devices due to their excellent ferroelectric properties.New Bi-based perovskite thin films Bi(Cu_(1/2)Ti_(1/2))O_(3)–PbTiO_(3)(BCT–PT) are deposited on Pt(111)/Ti/SiO_(2)/Si substrates in the present study by the traditional sol–gel method.Their structures and related ferroelectric and fatigue characteristics are studied in-depth.The BCT–PT thin films exhibit good crystallization within the phase-pure perovskite structure,besides,they have a predominant(100) orientation together with a dense and homogeneous microstructure.The remnant polarization(2P_(r)) values at 30 μC/cm^(2) and 16 μC/cm^(2) are observed in 0.1BCT–0.9PT and 0.2BCT–0.8PT thin films,respectively.More intriguingly,although the polarization values are not so high,0.2BCT–0.8PT thin films show outstanding polarization fatigue properties,with a high switchable polarization of 93.6% of the starting values after 10^(8) cycles,indicating promising applications in ferroelectric memories.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.52272116 and 12002400)the Natural Science Foundation of Shandong Province (Grant No.ZR2021ME096)the Youth Innovation Team Project of Shandong Provincial Education Department (Grant No.2019KJJ012)。
文摘Pb(Mg_(1/3)Nb_(2/3))O_(3)–PbTiO_(3)(PMN-PT)piezoelectric ceramics have excellent piezoelectric properties and are used in a wide range of applications.Adjusting the solid solution ratios of PMN/PT and different concentrations of elemental doping are the main methods to modulate their piezoelectric coefficients.The combination of these controllable conditions leads to an exponential increase of possible compositions in ceramics,which makes it not easy to extend the sample data by additional experimental or theoretical calculations.In this paper,a physics-embedded machine learning method is proposed to overcome the difficulties in obtaining piezoelectric coefficients and Curie temperatures of Sm-doped PMN-PT ceramics with different components.In contrast to all-data-driven model,physics-embedded machine learning is able to learn nonlinear variation rules based on small datasets through potential correlation between ferroelectric properties.Based on the model outputs,the positions of morphotropic phase boundary(MPB)with different Sm doping amounts are explored.We also find the components with the best piezoelectric property and comprehensive performance.Moreover,we set up a database according to the obtained results,through which we can quickly find the optimal components of Sm-doped PMN-PT ceramics according to our specific needs.
文摘Nanocrystalline rare earth mixed oxides SmFe_(1-x)Co_xO_(3-delta) wereprepared by sol-gel method at 1 073 K for 2 h calcination and characterized by X-ray diffraction(XRD) and scanning electron microscope (SEM). The results show that SmFe_(1-x)Co_xO_(3-delta) hasthe structure of perovskite type. The conductivity of the materials increases with the temperaturerising and the maximum conductivity at 1 073 K is 2.6 S/cm with the best mole ratio of Fe^(3+) toCo^(3+) being 1: 4. This kind of oxide is a conductive ceramic material by means of conduction ofelectron and oxygen anion.
文摘Quantum chemistry calculations of La , Ca modified and pure PbTiO\-3 nanocrystals were carried out by means of the cluster model in DFT DVM calculating program on which the regularity of the charge distribution was drawn. The analysis of the density of state(DOS) showed that when the cubic phase PbTiO 3 nanocrystal is changed into tetragonal phase, the interaction among Ti 3d , O 2p , and Pb 6p atomic orbitals causes the dipole moment and spontaneous polarization on the axis of the crystal, which resulted in the appearance of ferroelectric phase. At the same time, the dipole moment and the intensity of the spontaneous polarization were calculated as well.
文摘Nanocrystalline TiO2 was prepared by high frequency plasma chemical vapor deposition (HF-PCVD). The effects of additive AlCl3 on crystal phase, particle size and microstructurai parameters of TiO2 nanocrystallites were investigated by X-ray diffraction(XRD) and transmission electron microscopy (TEM). The nanocrystallites obtained experimentally are mixture of anatase and rutile, the uniform diameters of particles are about 30 nm. The phase transformation from anatase to rutile was accelerated by AlCl3, and rutile content is increased from 26.7 wt pct to 53.6 wt pct with increasing of addition of AlCl3 from 0.0 wt pct to 5.0 wt pct. The particle size is reduced and the size distribution becomes very narrow. The crystal lattice constants have the trend to decrease, and celi volumes appear as shrinkable.
文摘Nanocrystalline monoclinic and cubic Gd 2O 3∶Eu with different Eu 3+ concentration were prepared using glycine-nitrate combustion synthesis. By changing the ratio of glycine to nitrate and proper heat treatment, pure monoclinic and cubic Gd 2O 3∶Eu with particle size less than 40 nm can be easily formed. Under ultraviolet excitation, main emission of Eu 3+ ( 5D 0→ 7F 2) locates at 624 nm in monoclinic Gd 2O 3∶Eu and 611 nm in cubic sample. In excitation spectrum two broad bands corresponding to the host absorption and charge transfer state (CTS) and f-f transitions of Gd 3+ and Eu 3+ were observed and discussed. The quenching concentration of monoclinic and cubic Gd 2O 3∶Eu is 10% and 15%, respectively, both of which are much higher than that of bulk Gd 2O 3∶Eu.
文摘The gaseous Pr-penetration is a new method to modify ceramics, which is expected to be a promising method for producing new conductor ceramic materials. The gaseous penetration of Pr into PbTiO_3 ceramics and their improved electric properties were reported. Through XRD, EPMA and SEM analysis,it is confirmed that the gaseous penetration makes Pr enter into PbTiO_3 ceramics, and the new compound of Pr_2Ti_2O_7 is formed by the penetration of Pr in the gaseous state. The formed new Pr_2Ti_2O_7-PbTiO_3 ceramic materials have a significant change in electric properties. The room temperature resistivity decreases from 2.0×10^(10) Ω·m to 9.487 Ω·m. The grain resistance and the grain boundary resistance decrease with increase in temperature, and the PTCR effect disappears. The tendency of transition to a conductive body is manifest.
基金Funded by Open Foundation of State Key Laboratory of AdvancedTechnologyfor Materials Synthesis and Processing, Wuhan Universi-ty of Technology, the Post PhD Science Foundation of China(2003034504) andthe Foundation of Wuhan University of Technol-ogy(2003XJJ202)
文摘The rods that were shaped from nanocrystalline WC- 10.21 Co-0.42 VC/ Cr3 C2 （ wt% ） composite powders by using powder extrusion molding （PEM） were investigated. The nanocrystalline WC- 10.21 Co- 0. 42 VC/ Cr3 C2 （ wt% ） composite powders were prepared by the spray thermal decomposition-continuous reduction and carburization technology. In order to improve the properties of rods shaped by using powder extrusion molding, the cold isostatic pressing （CIP） technology was used before or after debinding. Specimens were siutered by vacuum siutering and hot isostatic pressing （HIP）. The density, Rockwell A hardness, magnetic coercivity , and magnetic saturation induction of siutered specimen were measured. The microstructure of the green bodies and the siutered specimens was studied by scanning electron microscopy （SEM）. Results show that the rod formed by using powder extrusion molding after debinding and followed by cold isostatic pressing can be siutered to 99.5% density of composite cemented carbide rods with an average grain size of about 200- 300 nm, magnetic coercivity of 30.4 KA / m, Rockwell A hardness of 92.6 and magnetic saturation induction of 85% . Superfine WC- 10 Co cemented carbide rods with excellent properties were obtained.
文摘Alumina (Al2O3) has been synthesized through combustion synthesis (CS) technique. The calcined products were characterized using X-ray diffractional analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermo-gravimetric analysis (TGA). TG-DTA results reveal the various stages involved in transition from γ-phase to α-Al2O3 phase. The first phase γ-Al2O3 was presented in the temperature range from 600°C-875°C as deduced from the XRD patterns with cubic crystal structure. The second stage occurs in the temperature range from 900°C-1000°C. In the final step, above 1000°C, the aluminium oxide appears completely as α-Al2O3, showing high crystallinity. The particle sizes are closely related to γ- to α-Al2O3 phase transition.
文摘Nanocrystalline rare earth mixed oxides DyFe x Co 1- x O 3- δ were prepared by sol gel method and characterized by X ray diffraction (XRD), thermogravimetric analysis (TG DTA) and scanning electron microscope (SEM). The results show that DyFe x Co 1- x O 3- δ has the structure of perovskite type at 800 ℃ for 2 h calcination. The conductivity of the materials at different temperature was measured by four probe instrumentation and two pole method. The results show that the conductivity of mixed oxides DyFe x Co 1- x O 3- δ is higher than those of un mixed oxides DyFeO 3 and DyCoO 3 and the conductivity is the best at x =0.8 in the matter of DyFe x Co 1- x O 3- δ . The conductivity of these materials always increases with the temperature rising and there is an apparent change between 600 and 800 ℃. However, the spinodals are different with different ration of Fe 3+ and Co 3+ . This kind of oxide is a conductive pottery material.
基金the National Natural Science Foundation of China (20571020)
文摘La2O3 and Ce2O3 were penetrated into PbTiO3 to obtain conductive powders, and then they were mixed with polyurethane and butyl acetate to prepare conductive coatings. The results showed that the electric property of modified PbTiO3 powders was improved by penetration of La2O3 and Ce2O3. XRD patterns showed that some new compounds such as La2Ti6O15, CeTi21O38 and Pb0.634La0.209Ti0.948O2.284 were formed, which led to the rapid increase of conductivity. The resistivity of modified PbTiO3 powders decreased to 3.88 Ω·m. The coatings using modified PbTiO3 powders as fillings also had a good conductivity. When the PbTiO3 powders were 10% and antisettle agent (bentonite) content was 0.50%, and mass ratio between polyurethane and butyl acetate was 1.05, the surface resistivity of the coatings fell down to 1.3×108 Ω·m. This kind of conductive coatings could be used in electromagnetic shielding.
