In dynamic problems the electric and magnetic fields are inseparable. At the same time, a multitude of electrostatic and magnetostatic effects permit mutually independent description. This separation appears to be pos...In dynamic problems the electric and magnetic fields are inseparable. At the same time, a multitude of electrostatic and magnetostatic effects permit mutually independent description. This separation appears to be possible and thermodynamically consistent when the bulk energy density depends only on the polarization density or, alternatively, on the magnetization density. However, when the bulk energy density depends simultaneously on the both densities, then, the electrostatic and magnetostatic effects should be studied together. There appear interesting cross-effects;among those are the change of the internal electrostatic field inside a specimen under the influence of the external magnetic fields, and vice versa. Below, in the framework of thermodynamic approach the boundary value problem for magnetoelectric plate is formulated and analyzed. The exact solution is established for the isotropic pyroelectric plate.展开更多
Combining microwave radiation with photocatalytic systems is a promising method to inhibit photogenerated electron-hole recombination and enhance the photocatalytic reaction performance. In this study, we have designe...Combining microwave radiation with photocatalytic systems is a promising method to inhibit photogenerated electron-hole recombination and enhance the photocatalytic reaction performance. In this study, we have designed Pd/Pb TiO3 catalysts that can use both microwave fields and photocatalysis. Benefiting from the synergistic effect of microwave field and UV light, the Pb TiO3 crystals convert thermal energy into electrical energy via the pyroelectricity effect, generating positive and negative charges(q+ and q-), while Pd nanoparticles significantly improve the quantum efficiency of the photocatalytic process. The composite catalyst significantly enhances the reaction rate and selectivity of the model Suzuki coupling reaction performed with bromobenzene. Microwave fields can directly act on chemical systems, promoting or changing various chemical reactions in unique ways.展开更多
The pyroelectric medium is an important material in the application of smart materials and structures. It is necessary to systematically discuss ail kinds of variational principles which play a very significant role i...The pyroelectric medium is an important material in the application of smart materials and structures. It is necessary to systematically discuss ail kinds of variational principles which play a very significant role in the fundamental theory of mechanics and numerical analysis method. This paper firstly gives the quasi-static and the dynamic variational principles,then the principles for eigen problems. As a simple example, the principle was finally applied to derive the fundamental, equations for an anisotropic piezoelectric plate.展开更多
Single-crystal X-ray diffraction structural data of four Fe-Mg tourmalines with different Fe contents from Xinjiang, Sichuan, and Yunnan Provinces, China, were collected at room temperature and-100oC. The intrinsic di...Single-crystal X-ray diffraction structural data of four Fe-Mg tourmalines with different Fe contents from Xinjiang, Sichuan, and Yunnan Provinces, China, were collected at room temperature and-100oC. The intrinsic dipole moments of polyhedra and the total intrinsic dipole moment of the unit cell were calculated. By comparing the intrinsic electric dipole moments of the X, Y, Z, T, and B site polyhedra, it is found that the T site polyhedron makes the greatest contribution to the total intrinsic dipole moment. The pyroelectric coefficients of four Fe-Mg tourmalines were experimentally determined, and the influence of intrinsic dipole moments on their pyroelectric properties was inves-tigated. The experimental results show that, compared with the case at room temperature, the intrinsic dipole moments change with the total Fe content at-100oC in a completely different way. With the decrease of temperature, the total intrinsic dipole moments of tourmaline de-crease. Over the same temperature interval, the pyroelectric coefficients increase with the increase in intrinsic dipole moment.展开更多
Previously, synthetic hexagonal bismuth sulfide iodide (polar space group P63, a = 15.629(3) ?, c = 4.018(1) ?, Z = 2) has been described by the rather unsatisfactory fractional formula Bi19/3IS9 [1] 08D0C9EA79F9BACE1...Previously, synthetic hexagonal bismuth sulfide iodide (polar space group P63, a = 15.629(3) ?, c = 4.018(1) ?, Z = 2) has been described by the rather unsatisfactory fractional formula Bi19/3IS9 [1] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400310037003600350038003400370039000000 -[3] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400310037003600350038003400370036000000 . A redetermination of the structure using old but reliable photographic intensity data indicated the presence of additional split positions and reduced atomic occupancies. From the observed pattern of this “averaged” structure a consistent model of a superstructure with lattice parameters of a' = √13·a = 56.35(1) ?, c' = c, and a formula Bi5-x(Bi2S3)39I12S emerged, with 2 formula units in a cell of likewise P63 space group. Structural modulation may be provoked by the space the lone electron pair of Bi requires. When Bi on the 0, 0, z position of the “averaged” cell is transferred to two general six-fold sites and one unoccupied twofold one of the super-cell, more structural stability is guaranteed due to compensation of its basal plane dipole momentum. Owing to the limited intensity data available, more details of the superstructure are not accessible yet. Some physical properties and solar cell application are discussed together with suggestions of ambient temperature synthesis routes of c-axis oriented nano-rod sheets.展开更多
The CdS/Bi_(2)S_(3) supported three-dimensional(3D)porous faveolate carbon structure(CdS/Bi_(2)S_(3)@C)composite photocatalyst was constructed.Bi_(2)S_(3) nanoparticles are regarded as photothermal agents and pyroelec...The CdS/Bi_(2)S_(3) supported three-dimensional(3D)porous faveolate carbon structure(CdS/Bi_(2)S_(3)@C)composite photocatalyst was constructed.Bi_(2)S_(3) nanoparticles are regarded as photothermal agents and pyroelectric materials to absorb near infrared light(NIR)and convert it into heat.3D porous faveolate of carbon acts as incubator to reduce heat loss and optimize photothermal effects.There is a greater fluctuating temperature difference(ΔΤ)between photothermal effect of Bi_(2)S_(3) and cold photocatalytic system.This enhances the pyroelectric effect that Bi_(2)S_(3) undergoes spontaneous polarization and releases the surface charge.Therefore,the separation of electrons and holes in the CdS photocatalyst can be induced.The COMSOL simulation results show that,the higher pyroelectric potential producted by largerΔΤis more favorable to the photocatalytic process.The hydrogen evolution rate of CdS/Bi_(2)S_(3)@C photocatalyst can reach 5.88 mmol·g^(-1)·h^(-1) with excellent cycle stability.展开更多
A gradient refractive structured NiCr film that has a high extinction coefficient at far infrared range(8-μm–24 μm) is presented as an absorber for pyroelectric infrared detectors. The absorber features high absorp...A gradient refractive structured NiCr film that has a high extinction coefficient at far infrared range(8-μm–24 μm) is presented as an absorber for pyroelectric infrared detectors. The absorber features high absorption efficiency due to the low reflection off the structured surface and high absorption across the film thickness. The refractive index and extinction coefficient are extracted using spectroscopic ellipsometry. It is found that the single NiCr film exhibits an increasing refractive index as the gas atmosphere pressure increases, hence the three-layer gradient NiCr absorber can be fabricated by adjusting the gas atmosphere pressure during sputtering deposition. Essential Macleod software has been used to generate an efficient film structure design and the calculations show similar absorptance trend compared to the experimental measurement result. The results indicate that the gradient refractive structured metal thin film absorber can provide high absorption for applications in thermal sensing.展开更多
The organic–inorganic hybrid(C2H5NH3)2 CuCl4(EA2CuCl4) single crystals are prepared by the solvothermal condition method. The x-ray diffraction, scanning electron microscopy, dielectric permittivity, pyroelectric cur...The organic–inorganic hybrid(C2H5NH3)2 CuCl4(EA2CuCl4) single crystals are prepared by the solvothermal condition method. The x-ray diffraction, scanning electron microscopy, dielectric permittivity, pyroelectric current, and heat capacity are used to systematically investigate the electrocaloric performances of EA2CuCl4. The pyroelectric currents are measured under various voltages, and the electrocaloric effect(ECE) is calculated. Its ECE exhibits an isothermal entropy change of 0.0028 J/kg·K under an electric field of 30 kV/cm associated with a relatively broad temperature span. Further, the maximum pyroelectric coefficient(p) is 4× 10^-3 C/m^2·K and the coefficient β for generating ECE from electric displacement D is 1.068× 10^8 J·cm·K^-1·C^-2 at 240 K. Our results indicate that the ECE behavior of organic–inorganic hybrid EA2CuCl4 is in accordance with Jona and Shirane’s opinion in which the ECE should occur both below and above the Curie temperature Tc.展开更多
In this paper, the effective pyroelectric coefficient and polarization offset of the compositionally step-like graded multilayer ferroelectric structures have been studied by use of the first-principles approach. It i...In this paper, the effective pyroelectric coefficient and polarization offset of the compositionally step-like graded multilayer ferroelectric structures have been studied by use of the first-principles approach. It is exhibited that the dielectric gradient has a nontrivial influence on the effective pyroelectric coefficient, but has a little influence on the polarization offset; and the polarization gradient plays an important role in the abnormal hysteresis loop phenomenon of the co.mpositionally step-like graded ferroelectric structures. Moreover, the origin of the polarization offset is explored,which can be attributed to the polarization gradient in the compositionally step-like graded structure.展开更多
PST ferroelectric ceramics were fabricated successfully by a two-step method, i e first, PbTiO3 and SrTiO3 were sintered respectively, then mixed and sintered together. The process and characteristics of PST ferroelec...PST ferroelectric ceramics were fabricated successfully by a two-step method, i e first, PbTiO3 and SrTiO3 were sintered respectively, then mixed and sintered together. The process and characteristics of PST ferroelectric ceramics were introduced and researched. Their dielectric and pyroelectric characteristics are as follows dielectric constant 10^4 order, low dielectric loss （lower than 3.0% in the working frequency range of 1-1 000 kHz）, saturation polarization intensity 10^-1 C/m^2 order, and pyroelectric coefficient 10^-3 C/m^2·K order.展开更多
In pyroelectric materials there is a spontaneous dielectric polarization.When raising the temperature,then a voltage appears in the system.In the present manuscript a phenomenological theory of pyroelectricity is deve...In pyroelectric materials there is a spontaneous dielectric polarization.When raising the temperature,then a voltage appears in the system.In the present manuscript a phenomenological theory of pyroelectricity is developed.展开更多
Pyroelectric multi-walled carbon nanotubes:polyvinylidene fluoride (PVDF:MWCT) composite films have been fabriccated by the solution casting technique. The pyroelectric and dielectric properties of the composite films...Pyroelectric multi-walled carbon nanotubes:polyvinylidene fluoride (PVDF:MWCT) composite films have been fabriccated by the solution casting technique. The pyroelectric and dielectric properties of the composite films were examined for their use in uncooled infrared detectors. The properties measured include: 1) dielectric constants and 2) pyroelec- tric coefficient as a function of temperature. From the foregoing parameters, materials Figures-of-merit, for infrared detection and thermal-vidicons, were calculated. The results indicated Figures-of-merit of composite film were higher than pristine polyvinylidene fluoride films.展开更多
It is desirable but always challenging to develop a cutting-edge tumor treatment strategy with high therapeutic efficacy,lesiontargeted precision and mild accessibility.Compared to traditional treatment modalities,pho...It is desirable but always challenging to develop a cutting-edge tumor treatment strategy with high therapeutic efficacy,lesiontargeted precision and mild accessibility.Compared to traditional treatment modalities,photodynamic therapy has been widely studied since the generation of reactive oxygen species(ROS)at cancerous lesions unprecedentedly offers a convenient approach for localized tumor eliminations.Nevertheless,the consumption of oxygen for ROS production in a hypoxic tumor microenvironment has dramatically limited its feasibility and efficacy.Herein,the engineered nanocomposites of BTO@PDA-ICGHA with photodynamic and pyroelectric performances have been fabricated and applied to the photodynamic-pyroelectric dynamic treatments.The continuing ROS production derived from intracellular oxygen(O_(2))and water(H_(2)O)by laser irradiation contributed to the superb tumor cell apoptosis and significant tumor growth inhibition.Thus,this study has validated a new concept by depositing the engineered nanocomposites at the tumor just like Trojan horses,facilitating ROS release as killers and exerting the NIR-induced cell apoptosis and tumor growth inhibition with high therapeutic efficiency and expectable translational perspectives.展开更多
During the past few decades, pyroelectric sensors have attracted extensiveattention due to their prominent features. However, their effectiveness is hinderedby low electric output. In this study, the laser processed l...During the past few decades, pyroelectric sensors have attracted extensiveattention due to their prominent features. However, their effectiveness is hinderedby low electric output. In this study, the laser processed lithium niobate(LPLN) wafers are fabricated to improve the temperature–voltage response.These processed wafers are utilized to construct pyroelectric sensors as well ashuman–machine interfaces. The laser induces escape of oxygen and the formationof oxygen vacancies, which enhance the charge transport capability on thesurface of lithium niobate (LN). Therefore, the electrodes gather an increasedquantity of charges, increasing the pyroelectric voltage on the LPLN wafers toa 1.3 times higher voltage than that of LN wafers. For the human–machineinterfaces, tactile information in various modes can be recognized by a sensorarray and the temperature warning system operates well. Therefore, the lasermodification approach is promising to enhance the performance of pyroelectricdevices for applications in human–machine interfaces.展开更多
The BiFeO_(3)/g-C_(3)N_(4) heterostructure,which is fabricated via a simple mixing–calcining method,benefits the significant enhancement of the pyrocatalytic performance.With the growth of g-C_(3)N_(4) content in the...The BiFeO_(3)/g-C_(3)N_(4) heterostructure,which is fabricated via a simple mixing–calcining method,benefits the significant enhancement of the pyrocatalytic performance.With the growth of g-C_(3)N_(4) content in the heterostructure pyrocatalysts from 0 to 25%,the decomposition ratio of Rhodamine B(RhB)dye after 18 cold-hot temperature fluctuation(25-65℃)cycles increases at first and then decreases,reaching a maximum value of~94.2%at 10%while that of the pure BiFeO_(3) is~67.7%.The enhanced dye decomposition may be due to the generation of the internal electric field which strengthens the separation of the positive and negative carriers and further accelerates their migrations.The intermediate products in the pyrocatalytic reaction also have been detected and confirmed,which proves the key role of the pyroelectric effect in realizing the dye decomposition using BiFeO_(3)/g-C_(3)N_(4) heterostructure catalyst.The pyroelectric BiFeO_(3)/g-C_(3)N_(4) heterostructure shows the potential application in pyrocatalytically degrading dye wastewater.展开更多
Real-time, continuous-wave terahertz （THz） imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera...Real-time, continuous-wave terahertz （THz） imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.展开更多
Pure Ko.sNao sNbO3(KNN)and KNN doped with Lit(6%mole),Lat(1.66%,5%,6%mole),and Ti+t(10%mole)were prepared by mixture of oxides using high-energy milling and conventional solid-state reaction.The effects of the dopant ...Pure Ko.sNao sNbO3(KNN)and KNN doped with Lit(6%mole),Lat(1.66%,5%,6%mole),and Ti+t(10%mole)were prepared by mixture of oxides using high-energy milling and conventional solid-state reaction.The effects of the dopant on the physical properties of pure KNN have been evaluated based on the structural,ferroelectric,pyroelectric,and dielectric measurements.The XRD measurements show that KNN pure sample contains a mixture of monoclinic and orthorhombic crystalline phases,with a slightly higher concentration of monoclinic phase.In contrast,all doped samples show a higher concentration of the orthorhombic phase,as well as the presence of a secondary phase(K6Nb10.8O3o),also detected by Raman measurements.The samples with a higher concentration of this secondary phase,also present greater dielectric losses and lower values of remnant polarization.The dielectric measurements allowed us to detect temperatures of structural transitions(orthorhombic-tetragonal,O-T)previous to the ferroelectric paraelectric transition(tetragonal-cubic,T-C),and also in this set of samples,a direct correlation was found between the values of remnant polarization and the corresponding pyroelectric signal response.展开更多
The pyroelectric effect of phase transition induced with temperature in Nb-modified Pb(Zr,Sn,Ti)O3 antiferroelectric-ferroelectric ceramics is studied. Experimental results reveal that the phase transitions are accomp...The pyroelectric effect of phase transition induced with temperature in Nb-modified Pb(Zr,Sn,Ti)O3 antiferroelectric-ferroelectric ceramics is studied. Experimental results reveal that the phase transitions are accompanied with marked pyroelectric peaks, there exists the close relation between the type of phase transition and the shape of pyroelectric peak. Because of the variations of phase transition, various pyroelectric spectra result. The pyroelectric spectrum can display the polarization effect and some inferior phase transitions with temperature variations, such as antiferroelectric AFEA-AFEB or ferroelectric FEL-FEH transition, which are not detected by the conventional dielectric measurement.展开更多
Large pyroelectric and energy harvesting properties have been attracting increasing attentions due to the practical applications in infrared detectors and energy harvesting technologies.Ferroelectricantiferroelectric(...Large pyroelectric and energy harvesting properties have been attracting increasing attentions due to the practical applications in infrared detectors and energy harvesting technologies.Ferroelectricantiferroelectric(FE-AFE)phase transitions are usually accompanied by a sharp drop in polarization,which will lead to excellent pyroelectric properties and energy harvesting density.Therefore,FE-AFE phase boundary design is an effective strategy to develop new pyroelectric materials.In this paper,Pb(Lu_(1/2)Nb_(1/2))O_(3)-PbTiO_(3) (PLN-PT)single crystals with FE-AFE phase transitions were obtained by molten salt growth method.The temperature-induced FE-AFE phase transition was verified by temperaturedependent macrodomain structure,DSC curves and dielectric properties.Obviously,PLN-PT crystals display excellent peak pyroelectric coefficient(~6.8μC/(cm^(2)·K)with a maximum depolarization temperature of 118℃.Meanwhile,the pyroelectric energy harvesting density is as high as 2.62 J/cm3,which is much higher than other pyroelectric materials.The results reveal that the PLN-PT crystal is a promising candidate for infrared detectors and energy harvesting devices.展开更多
The characterization of pyroelectric materials is essential for the design of pyroelectric-based devices.Pyroelectric current measurement is the commonly employed method,but can be complex and requires surface electro...The characterization of pyroelectric materials is essential for the design of pyroelectric-based devices.Pyroelectric current measurement is the commonly employed method,but can be complex and requires surface electrodes.Here,we present noncontact electrostatic voltmeter measurements as a simple but highly accurate alternative,by assessing thermally-induced pyroelectric surface potential variations.We introduce a refined model that relates the surface potential variations to both the pyroelectric coefficient and the characteristic figure of merit(FOM)and test the model with square-shaped samples made from PVDF,LiNbO3 and LiTaO3.The characteristic pyroelectric coefficient for PVDF,LiNbO3 and LiTaO3 was found to be 33.4,59.9 and 208.4μC m−2 K−1,respectively.These values are in perfect agreement with literature values,and they differ by less than 2.5%from values that we have obtained with standard pyroelectric current measurements for comparison.展开更多
文摘In dynamic problems the electric and magnetic fields are inseparable. At the same time, a multitude of electrostatic and magnetostatic effects permit mutually independent description. This separation appears to be possible and thermodynamically consistent when the bulk energy density depends only on the polarization density or, alternatively, on the magnetization density. However, when the bulk energy density depends simultaneously on the both densities, then, the electrostatic and magnetostatic effects should be studied together. There appear interesting cross-effects;among those are the change of the internal electrostatic field inside a specimen under the influence of the external magnetic fields, and vice versa. Below, in the framework of thermodynamic approach the boundary value problem for magnetoelectric plate is formulated and analyzed. The exact solution is established for the isotropic pyroelectric plate.
文摘Combining microwave radiation with photocatalytic systems is a promising method to inhibit photogenerated electron-hole recombination and enhance the photocatalytic reaction performance. In this study, we have designed Pd/Pb TiO3 catalysts that can use both microwave fields and photocatalysis. Benefiting from the synergistic effect of microwave field and UV light, the Pb TiO3 crystals convert thermal energy into electrical energy via the pyroelectricity effect, generating positive and negative charges(q+ and q-), while Pd nanoparticles significantly improve the quantum efficiency of the photocatalytic process. The composite catalyst significantly enhances the reaction rate and selectivity of the model Suzuki coupling reaction performed with bromobenzene. Microwave fields can directly act on chemical systems, promoting or changing various chemical reactions in unique ways.
基金The work is supported by the Doctoral Education Foundation.
文摘The pyroelectric medium is an important material in the application of smart materials and structures. It is necessary to systematically discuss ail kinds of variational principles which play a very significant role in the fundamental theory of mechanics and numerical analysis method. This paper firstly gives the quasi-static and the dynamic variational principles,then the principles for eigen problems. As a simple example, the principle was finally applied to derive the fundamental, equations for an anisotropic piezoelectric plate.
基金financially supported by the National Natural Science Foundation of China(No.40672031)
文摘Single-crystal X-ray diffraction structural data of four Fe-Mg tourmalines with different Fe contents from Xinjiang, Sichuan, and Yunnan Provinces, China, were collected at room temperature and-100oC. The intrinsic dipole moments of polyhedra and the total intrinsic dipole moment of the unit cell were calculated. By comparing the intrinsic electric dipole moments of the X, Y, Z, T, and B site polyhedra, it is found that the T site polyhedron makes the greatest contribution to the total intrinsic dipole moment. The pyroelectric coefficients of four Fe-Mg tourmalines were experimentally determined, and the influence of intrinsic dipole moments on their pyroelectric properties was inves-tigated. The experimental results show that, compared with the case at room temperature, the intrinsic dipole moments change with the total Fe content at-100oC in a completely different way. With the decrease of temperature, the total intrinsic dipole moments of tourmaline de-crease. Over the same temperature interval, the pyroelectric coefficients increase with the increase in intrinsic dipole moment.
文摘Previously, synthetic hexagonal bismuth sulfide iodide (polar space group P63, a = 15.629(3) ?, c = 4.018(1) ?, Z = 2) has been described by the rather unsatisfactory fractional formula Bi19/3IS9 [1] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400310037003600350038003400370039000000 -[3] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400310037003600350038003400370036000000 . A redetermination of the structure using old but reliable photographic intensity data indicated the presence of additional split positions and reduced atomic occupancies. From the observed pattern of this “averaged” structure a consistent model of a superstructure with lattice parameters of a' = √13·a = 56.35(1) ?, c' = c, and a formula Bi5-x(Bi2S3)39I12S emerged, with 2 formula units in a cell of likewise P63 space group. Structural modulation may be provoked by the space the lone electron pair of Bi requires. When Bi on the 0, 0, z position of the “averaged” cell is transferred to two general six-fold sites and one unoccupied twofold one of the super-cell, more structural stability is guaranteed due to compensation of its basal plane dipole momentum. Owing to the limited intensity data available, more details of the superstructure are not accessible yet. Some physical properties and solar cell application are discussed together with suggestions of ambient temperature synthesis routes of c-axis oriented nano-rod sheets.
文摘The CdS/Bi_(2)S_(3) supported three-dimensional(3D)porous faveolate carbon structure(CdS/Bi_(2)S_(3)@C)composite photocatalyst was constructed.Bi_(2)S_(3) nanoparticles are regarded as photothermal agents and pyroelectric materials to absorb near infrared light(NIR)and convert it into heat.3D porous faveolate of carbon acts as incubator to reduce heat loss and optimize photothermal effects.There is a greater fluctuating temperature difference(ΔΤ)between photothermal effect of Bi_(2)S_(3) and cold photocatalytic system.This enhances the pyroelectric effect that Bi_(2)S_(3) undergoes spontaneous polarization and releases the surface charge.Therefore,the separation of electrons and holes in the CdS photocatalyst can be induced.The COMSOL simulation results show that,the higher pyroelectric potential producted by largerΔΤis more favorable to the photocatalytic process.The hydrogen evolution rate of CdS/Bi_(2)S_(3)@C photocatalyst can reach 5.88 mmol·g^(-1)·h^(-1) with excellent cycle stability.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61875031 and 61421002)
文摘A gradient refractive structured NiCr film that has a high extinction coefficient at far infrared range(8-μm–24 μm) is presented as an absorber for pyroelectric infrared detectors. The absorber features high absorption efficiency due to the low reflection off the structured surface and high absorption across the film thickness. The refractive index and extinction coefficient are extracted using spectroscopic ellipsometry. It is found that the single NiCr film exhibits an increasing refractive index as the gas atmosphere pressure increases, hence the three-layer gradient NiCr absorber can be fabricated by adjusting the gas atmosphere pressure during sputtering deposition. Essential Macleod software has been used to generate an efficient film structure design and the calculations show similar absorptance trend compared to the experimental measurement result. The results indicate that the gradient refractive structured metal thin film absorber can provide high absorption for applications in thermal sensing.
基金Project supported by the Fujian Institute of Innovation,Chinese Academy of Sciences(Grant No.FJCXY18040303)the Youth Innovation Promotion of the Chinese Academy of Sciences(Grant No.2013004)the National Natural Science Foundation of China(Grant Nos.51676198 and 51771067)
文摘The organic–inorganic hybrid(C2H5NH3)2 CuCl4(EA2CuCl4) single crystals are prepared by the solvothermal condition method. The x-ray diffraction, scanning electron microscopy, dielectric permittivity, pyroelectric current, and heat capacity are used to systematically investigate the electrocaloric performances of EA2CuCl4. The pyroelectric currents are measured under various voltages, and the electrocaloric effect(ECE) is calculated. Its ECE exhibits an isothermal entropy change of 0.0028 J/kg·K under an electric field of 30 kV/cm associated with a relatively broad temperature span. Further, the maximum pyroelectric coefficient(p) is 4× 10^-3 C/m^2·K and the coefficient β for generating ECE from electric displacement D is 1.068× 10^8 J·cm·K^-1·C^-2 at 240 K. Our results indicate that the ECE behavior of organic–inorganic hybrid EA2CuCl4 is in accordance with Jona and Shirane’s opinion in which the ECE should occur both below and above the Curie temperature Tc.
文摘In this paper, the effective pyroelectric coefficient and polarization offset of the compositionally step-like graded multilayer ferroelectric structures have been studied by use of the first-principles approach. It is exhibited that the dielectric gradient has a nontrivial influence on the effective pyroelectric coefficient, but has a little influence on the polarization offset; and the polarization gradient plays an important role in the abnormal hysteresis loop phenomenon of the co.mpositionally step-like graded ferroelectric structures. Moreover, the origin of the polarization offset is explored,which can be attributed to the polarization gradient in the compositionally step-like graded structure.
文摘PST ferroelectric ceramics were fabricated successfully by a two-step method, i e first, PbTiO3 and SrTiO3 were sintered respectively, then mixed and sintered together. The process and characteristics of PST ferroelectric ceramics were introduced and researched. Their dielectric and pyroelectric characteristics are as follows dielectric constant 10^4 order, low dielectric loss （lower than 3.0% in the working frequency range of 1-1 000 kHz）, saturation polarization intensity 10^-1 C/m^2 order, and pyroelectric coefficient 10^-3 C/m^2·K order.
文摘In pyroelectric materials there is a spontaneous dielectric polarization.When raising the temperature,then a voltage appears in the system.In the present manuscript a phenomenological theory of pyroelectricity is developed.
文摘Pyroelectric multi-walled carbon nanotubes:polyvinylidene fluoride (PVDF:MWCT) composite films have been fabriccated by the solution casting technique. The pyroelectric and dielectric properties of the composite films were examined for their use in uncooled infrared detectors. The properties measured include: 1) dielectric constants and 2) pyroelec- tric coefficient as a function of temperature. From the foregoing parameters, materials Figures-of-merit, for infrared detection and thermal-vidicons, were calculated. The results indicated Figures-of-merit of composite film were higher than pristine polyvinylidene fluoride films.
基金supported by the National Natural Science Foundation of China(82072057,82311540023)。
文摘It is desirable but always challenging to develop a cutting-edge tumor treatment strategy with high therapeutic efficacy,lesiontargeted precision and mild accessibility.Compared to traditional treatment modalities,photodynamic therapy has been widely studied since the generation of reactive oxygen species(ROS)at cancerous lesions unprecedentedly offers a convenient approach for localized tumor eliminations.Nevertheless,the consumption of oxygen for ROS production in a hypoxic tumor microenvironment has dramatically limited its feasibility and efficacy.Herein,the engineered nanocomposites of BTO@PDA-ICGHA with photodynamic and pyroelectric performances have been fabricated and applied to the photodynamic-pyroelectric dynamic treatments.The continuing ROS production derived from intracellular oxygen(O_(2))and water(H_(2)O)by laser irradiation contributed to the superb tumor cell apoptosis and significant tumor growth inhibition.Thus,this study has validated a new concept by depositing the engineered nanocomposites at the tumor just like Trojan horses,facilitating ROS release as killers and exerting the NIR-induced cell apoptosis and tumor growth inhibition with high therapeutic efficiency and expectable translational perspectives.
基金National Key Research and Development Program of China,Grant/Award Number:2023YFB3210400National Natural Science Foundation of China,Grant/Award Number:52102171+2 种基金Major Scientific and Technological Innovation Project of Shandong Province,Grant/Award Numbers:2021CXGC010603,2023CXGC010110Natural Science Foundation of Shandong Province,Grant/Award Numbers:ZR2021ZD20,ZR2020LLZ006,ZR2021JQ15,ZR2023LLZ008Innovative Team Project of Jinan,Grant/Award Number:2021GXRC019。
文摘During the past few decades, pyroelectric sensors have attracted extensiveattention due to their prominent features. However, their effectiveness is hinderedby low electric output. In this study, the laser processed lithium niobate(LPLN) wafers are fabricated to improve the temperature–voltage response.These processed wafers are utilized to construct pyroelectric sensors as well ashuman–machine interfaces. The laser induces escape of oxygen and the formationof oxygen vacancies, which enhance the charge transport capability on thesurface of lithium niobate (LN). Therefore, the electrodes gather an increasedquantity of charges, increasing the pyroelectric voltage on the LPLN wafers toa 1.3 times higher voltage than that of LN wafers. For the human–machineinterfaces, tactile information in various modes can be recognized by a sensorarray and the temperature warning system operates well. Therefore, the lasermodification approach is promising to enhance the performance of pyroelectricdevices for applications in human–machine interfaces.
基金supported by the National Natural Science Foundation of China(Nos.51872264 and 51778391)Shaanxi Provincial National Science Foundation of China(No.2020JM-579)+1 种基金Key Research and Development Program of Shaanxi Province,China(No.2020GXLH-Z-032)the Basic Public Welfare Research Program of Zhejiang Province,China(No.LGG18E020005)。
文摘The BiFeO_(3)/g-C_(3)N_(4) heterostructure,which is fabricated via a simple mixing–calcining method,benefits the significant enhancement of the pyrocatalytic performance.With the growth of g-C_(3)N_(4) content in the heterostructure pyrocatalysts from 0 to 25%,the decomposition ratio of Rhodamine B(RhB)dye after 18 cold-hot temperature fluctuation(25-65℃)cycles increases at first and then decreases,reaching a maximum value of~94.2%at 10%while that of the pure BiFeO_(3) is~67.7%.The enhanced dye decomposition may be due to the generation of the internal electric field which strengthens the separation of the positive and negative carriers and further accelerates their migrations.The intermediate products in the pyrocatalytic reaction also have been detected and confirmed,which proves the key role of the pyroelectric effect in realizing the dye decomposition using BiFeO_(3)/g-C_(3)N_(4) heterostructure catalyst.The pyroelectric BiFeO_(3)/g-C_(3)N_(4) heterostructure shows the potential application in pyrocatalytically degrading dye wastewater.
文摘Real-time, continuous-wave terahertz （THz） imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.
基金The authors express their thanks to CONACYT for funding this research through projects CB-240460 and LN-295261,and to LIDTRA for the facilities in the use of experimental infrastructure.
文摘Pure Ko.sNao sNbO3(KNN)and KNN doped with Lit(6%mole),Lat(1.66%,5%,6%mole),and Ti+t(10%mole)were prepared by mixture of oxides using high-energy milling and conventional solid-state reaction.The effects of the dopant on the physical properties of pure KNN have been evaluated based on the structural,ferroelectric,pyroelectric,and dielectric measurements.The XRD measurements show that KNN pure sample contains a mixture of monoclinic and orthorhombic crystalline phases,with a slightly higher concentration of monoclinic phase.In contrast,all doped samples show a higher concentration of the orthorhombic phase,as well as the presence of a secondary phase(K6Nb10.8O3o),also detected by Raman measurements.The samples with a higher concentration of this secondary phase,also present greater dielectric losses and lower values of remnant polarization.The dielectric measurements allowed us to detect temperatures of structural transitions(orthorhombic-tetragonal,O-T)previous to the ferroelectric paraelectric transition(tetragonal-cubic,T-C),and also in this set of samples,a direct correlation was found between the values of remnant polarization and the corresponding pyroelectric signal response.
文摘The pyroelectric effect of phase transition induced with temperature in Nb-modified Pb(Zr,Sn,Ti)O3 antiferroelectric-ferroelectric ceramics is studied. Experimental results reveal that the phase transitions are accompanied with marked pyroelectric peaks, there exists the close relation between the type of phase transition and the shape of pyroelectric peak. Because of the variations of phase transition, various pyroelectric spectra result. The pyroelectric spectrum can display the polarization effect and some inferior phase transitions with temperature variations, such as antiferroelectric AFEA-AFEB or ferroelectric FEL-FEH transition, which are not detected by the conventional dielectric measurement.
基金Project supported by the National Natural Science Foundation of China(51902307,11904362,11974349)Strategic Priority Research Program of the Chinese Academy of Sciences(XDB20000000)+1 种基金Youth Innovation Promotion Association CASScience and Technology Project of Fujian Province(2020H0038,2019H0052)。
文摘Large pyroelectric and energy harvesting properties have been attracting increasing attentions due to the practical applications in infrared detectors and energy harvesting technologies.Ferroelectricantiferroelectric(FE-AFE)phase transitions are usually accompanied by a sharp drop in polarization,which will lead to excellent pyroelectric properties and energy harvesting density.Therefore,FE-AFE phase boundary design is an effective strategy to develop new pyroelectric materials.In this paper,Pb(Lu_(1/2)Nb_(1/2))O_(3)-PbTiO_(3) (PLN-PT)single crystals with FE-AFE phase transitions were obtained by molten salt growth method.The temperature-induced FE-AFE phase transition was verified by temperaturedependent macrodomain structure,DSC curves and dielectric properties.Obviously,PLN-PT crystals display excellent peak pyroelectric coefficient(~6.8μC/(cm^(2)·K)with a maximum depolarization temperature of 118℃.Meanwhile,the pyroelectric energy harvesting density is as high as 2.62 J/cm3,which is much higher than other pyroelectric materials.The results reveal that the PLN-PT crystal is a promising candidate for infrared detectors and energy harvesting devices.
基金supported by the European Horizon 2020 grant“SensApp”under Grant Agreement No.829104.
文摘The characterization of pyroelectric materials is essential for the design of pyroelectric-based devices.Pyroelectric current measurement is the commonly employed method,but can be complex and requires surface electrodes.Here,we present noncontact electrostatic voltmeter measurements as a simple but highly accurate alternative,by assessing thermally-induced pyroelectric surface potential variations.We introduce a refined model that relates the surface potential variations to both the pyroelectric coefficient and the characteristic figure of merit(FOM)and test the model with square-shaped samples made from PVDF,LiNbO3 and LiTaO3.The characteristic pyroelectric coefficient for PVDF,LiNbO3 and LiTaO3 was found to be 33.4,59.9 and 208.4μC m−2 K−1,respectively.These values are in perfect agreement with literature values,and they differ by less than 2.5%from values that we have obtained with standard pyroelectric current measurements for comparison.
