Two different poling techniques-corona poling and contact poling in the backdrop of electro-optic （EO） polymer modulators are compared. A 3-layer structure EO polymer modulator is prepared for the poling. The poling...Two different poling techniques-corona poling and contact poling in the backdrop of electro-optic （EO） polymer modulators are compared. A 3-layer structure EO polymer modulator is prepared for the poling. The poling setups and procedures of these two different methods are given. It is found that a well-controlled precure step is very critical, otherwise it will result in either lower poling efficiency or damaged film. Experimental results show that contact poling does not create severe surface damage as corona poling and poling voltage is much lower, but corona poling provides higher EO effect than contact poling. Besides, contact poling can provide poling size as large as the substrate size.展开更多
High piezoelectric properties and superior thermal stability are both important indicators of piezoelectric ceramics serving at high temperature.However,since these properties are usually mutually exclusive,high perfo...High piezoelectric properties and superior thermal stability are both important indicators of piezoelectric ceramics serving at high temperature.However,since these properties are usually mutually exclusive,high performance and superior thermal stability are hard to achieve simultaneously.Here we report that a high piezoelectricity(d_(33)∼562 pC/N)and superior thermal stability(the variation is within 7%from 20 to 330℃)were both achieved in 0.4 mol%ZnO-doped 0.02Pb(Sb_(1/2)Nb_(1/2))-0.51PbZrO_(3)-0.47PbTiO_(3) by high-temperature poling.Compared with traditional poling method,high-temperature poling method forms a small-sized and highly oriented domain structure,which can effectively improve the piezoelectric and dielectric properties of piezoelectric ceramics.At the same time,the enhanced pinning effect of defect ions and stabilized domain structure due to high-temperature poling also contribute to the superior temperature stability of the piezoelectric and dielectric properties.This work provides an effective method for designing piezoelectric materials with high performance and good temperature stability for high temperature sensor applications.展开更多
In this paper, the poling properties of (PS)O-DCV, a derivative of poly (p-hydroxystyrene ), was reported. The investigations showed that the thermochromism correction, which was neglected in the literatures, should b...In this paper, the poling properties of (PS)O-DCV, a derivative of poly (p-hydroxystyrene ), was reported. The investigations showed that the thermochromism correction, which was neglected in the literatures, should be considered in the measurements of order parameter of poled films with electrochromism technique Here, another linear optical method, IR and polarized IR spectra for characterizing of poled films was suggested first time. The bulk second nonlinear optical coefficient d_(33) of poled films could be estimated by measured order parameter semi-qualitatively.展开更多
We studied cycle time （0.01-10 s with triangular input waves） and poling history （continuous versus fresh poling） dependent electric energy storage and discharge behaviors in poly（vinylidene fluoride-co-hexafluor...We studied cycle time （0.01-10 s with triangular input waves） and poling history （continuous versus fresh poling） dependent electric energy storage and discharge behaviors in poly（vinylidene fluoride-co-hexafluoropropylene） [P（VDF- HFP）] films using the electric displacement -- the electric field （D-E） hysteresis loop measurements. Since the permanent dipoles in PVDF are orientational in nature, it is generally considered that both charging and discharging processes should be time and poling history dependent. Intriguingly, our experimental results showed that the charging process depended heavily on the cycle time and the prior poling history, and thus the D-E hysteresis loops had different shapes accordingly. However, the discharged energy density did not change no matter how the D-E loop shape varied due to different measurements. This experimental result could be explained in terms of reversible and irreversible polarizations. The reversible polarization could be charged and discharged fairly quickly （〈 5 ms for each process）, while the irreversible polarization depended heavily on the poling time and the prior poling history. This study suggests that it is only meaningful to compare the discharged energy density for PVDF and its copolymer films when different cycle times and poling histories are used.展开更多
In attempts to fabricate thermally stable second-order nonlinear polymer thin films, we have investigated the second harmonic generation (SHG) from both nonlinear polymer and vip-host thin films. We have also invest...In attempts to fabricate thermally stable second-order nonlinear polymer thin films, we have investigated the second harmonic generation (SHG) from both nonlinear polymer and vip-host thin films. We have also investigated the role of capping on the SHG, temporal stability and relaxation of dipole alignment. Corona poling techniques were employed to orient the dopants into the noncentrosymmetric structure required to obtain the SHG. The effect of capping with a polymeric encapsulant below the glass transition temperature of the polymers on the unpoled and corona poled thin films was studied. Capping of the nonlinear polymer and vip host thin films have resulted in high SHG with good temporal stability. SHG signal falls drastically during the first 8 days after poling while no further significant decay in SHG signal was observed after about 33 days. Our investigations have identified the characteristics required for a good encapsulant on a non-con-ductive surface.展开更多
Electric field poling of electro-optic polymer(EOP)in hybrid waveguides is highly challenging due to the discontinuity in electric field distribution,which leads to a low Pockels electro-optic(EO)coefficient or dielec...Electric field poling of electro-optic polymer(EOP)in hybrid waveguides is highly challenging due to the discontinuity in electric field distribution,which leads to a low Pockels electro-optic(EO)coefficient or dielectric breakdown.We propose the segmented poling technique in Si_(3)N_(4)/EOP hybrid waveguides to address this challenge.Dipolar chromophores near an electrode interface first align with a weak poling electric field,and then a strong field is applied for the chromophore alignment near the waveguide interface.This technique effectively avoids dielectric breakdown,and the tuning efficiency of the EO Mach-Zender interferometer(MZI)filters is improved from 31.7 pm/V to higher than 50 pm/V,with a highest Pockels coefficient of 114 pm/V.展开更多
The high Tg polyimide embedded with a novel imidazol-typed chromophore 2-[5-(4-nitrostilbenyl)thienyl]-4,S-di(4-aniinophenyl)imidazole (NSTDAPI) was prepared using the 'simultaneous poling and polymerization' ...The high Tg polyimide embedded with a novel imidazol-typed chromophore 2-[5-(4-nitrostilbenyl)thienyl]-4,S-di(4-aniinophenyl)imidazole (NSTDAPI) was prepared using the 'simultaneous poling and polymerization' technique. The glass transition temperature (Fg) is 304℃ and the initial decomposition temperature (Td) is 330℃. The in-situ second harmonic generation (in-situ SHG) measurement was performed to study its poling behavior and the stability of the poling-induced orientation. The nonlinear optical (NLO) coefficient d33 of poled polyimide film is 32.2 pm/V at 1064 nm fundamental wavelength. The SHG signal of the poled polymer film was quite stable below 200℃, and then began to decay rapidly above 220℃. The half-decay temperature of dipole orientation for the film is 250℃.展开更多
Alternating current poling(ACP)in air by changing poling temperature(70e130℃)and voltages(2e6 kVrms/cm)on pseudo-ternary 0.24 Pb(In_(1/2)Nb_(1/2))O_(3)-0.46 Pb(Mg1/3Nb_(2/3))O3-0.30PbTiO_(3)(PIMN-0.30PT)single crysta...Alternating current poling(ACP)in air by changing poling temperature(70e130℃)and voltages(2e6 kVrms/cm)on pseudo-ternary 0.24 Pb(In_(1/2)Nb_(1/2))O_(3)-0.46 Pb(Mg1/3Nb_(2/3))O3-0.30PbTiO_(3)(PIMN-0.30PT)single crystals(SCs)manufactured by continuous-feeding Bridgman(CF BM)method was investigated.Free dielectric permittivity(εT 33/ε0)and piezoelectric constant(d33)were improved to be 7000 and 2340 pC/N,which were 29%higher than those of direct current poling(DCP)at 90℃ with 4 kV/cm(εT 33/ε0=5440,d_(33)=1810 pC/N).However,phase change temperature(Tpc)decreased from 94℃ to 78℃ as opposite results reported by other groups.We demonstrated that the high temperature(HT)ACP improved piezoelectric performance of CF BM SCs,however,the Tpc were different from other crystal growth method.The well-designed ACP process was a promising method for mass production not only to enhance the electrical properties for the pseudo-ternary SCs but also reduce the risk of breakdown and realizes organic solvent-free poling process.展开更多
BiFeO_(3)-BaTiO_(3) based ceramics are considered to be the most promising lead-free piezoelectric ceramics due to their large piezoelectric response and high Curie temperature.Since the piezoelectric response of piez...BiFeO_(3)-BaTiO_(3) based ceramics are considered to be the most promising lead-free piezoelectric ceramics due to their large piezoelectric response and high Curie temperature.Since the piezoelectric response of piezoelectric ceramics just appears after poling engineering,in this work,the domain evolution and microscopic piezoresponse were observed in-situ using piezoresponse force microscopy(PFM)and switching spectroscopy piezoresponse force microscopy(SS-PFM),which can effectively study the local switching characteristics of ferroelectric materials especially at the nanoscale.The new domain nucleation preferentially forms at the boundary of the relative polarization region and expands laterally with the increase of bias voltage and temperature.The maximum piezoresponse(Rs),remnant piezoresponse(Rrem),maximum displacement(Dmax)and negative displacement(Dneg)at 45 V and 120C reach 122,69,127 pm and 75 pm,respectively.Due to the distinct effect of poling engineering in full domain switching,the corresponding d33 at 50 kV/cm and 120C reaches a maximum of 205 pC/N,which is nearly twice as high as that at room temperature.Studying the evolution of ferroelectric domains in the poling engineering of BiFeO_(3)-BaTiO_(3)ceramics provides an insight into the relationship between domain structure and piezoelectric response,which has implications for other piezoelectric ceramics as well.展开更多
The effects of alternating current poling(ACP)at 80℃on electrical properties of[001]-oriented 0.72 Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.28PbTiO_(3)(PMN-28PT)single crystals(SCs)have been investigated.The square-wave ACP SCs p...The effects of alternating current poling(ACP)at 80℃on electrical properties of[001]-oriented 0.72 Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.28PbTiO_(3)(PMN-28PT)single crystals(SCs)have been investigated.The square-wave ACP SCs poled at high voltage(HV,5 kV_(rms)/cm)occasionally showed large fluctuations and low opposite values of piezoelectric coefficient(d_(33)=±1370 pC/N)in one plate.This revealed spuriousmode vibrations(SMV)of impedance spectrum.However,after depolarizing and repolarizing the sample with a sine-wave ACP at low voltage(LV,3.5 kV_(rms)/cm),the d_(33) enhanced to be 1720 pC/N(+26%)and did not exhibit large fluctuation or opposite values in one plate any more.The impedance spectrum became clean and the abnormal SMV disappeared.We proposed four possible mechanisms of the SMV,and speculate that the main cause maybe by macro-scale sub-domain structure and/or phase change in the main domain structure and/or phase in the SC plate due to the specific poling conditions not eternal mechanical damage of PMN-PT SCs.This study will be useful to realize a high d_(33) and improve other properties of PMN-PT ACP SC ultrasonic transducers without any SMV for high-frequency medical imaging equipment.展开更多
Based on the experimental results, three basic conclusions are summarized for the thermal/electric-field poling (TEFP) silica materials, with which the second-order nonlinear optical coefficient in the bulk silica gla...Based on the experimental results, three basic conclusions are summarized for the thermal/electric-field poling (TEFP) silica materials, with which the second-order nonlinear optical coefficient in the bulk silica glass after TEFP is calculated, and relationships between the coefficient and the applied voltage V 0 in the poling process and the thickness of the nonlinear layer created from the poling are obtained. Theoretical results show that the second-order susceptibility χ(2) and the second-harmonic efficiency η in the poled bulk glass are proportional to √V 0 and V 0 2 , respectively; χ(2)～0.2?1.6 pm/V for the bulk glass after the typical TEFP; χ(2) decreases with an increase in the poling time after the TEFP silica glass approximately reaches the steady state. Theoretical results are well consistent with the experimental reports.展开更多
Conductive ferroelectric domain walls have attracted increasing research interest in the field of nanoelectronics,and the fabrication technique for such domain walls is vital.In this study,we investigated in detail th...Conductive ferroelectric domain walls have attracted increasing research interest in the field of nanoelectronics,and the fabrication technique for such domain walls is vital.In this study,we investigated in detail the fabrication of conductive domain walls in x-cut congruent thin-film lithium niobate(TFLN)using an electrical-field poling technique.The ferroelectric domain structures can be controlled through the applied electrical field and applied pulse numbers,and the domain inversion process is related to the conduction characteristics of the domain walls.The domain structures in TFLN are revealed using confocal second-harmonic microscopy and piezoresponse force microscopy.The results provide further directions for the development and application of conductive domain walls in TFLN.展开更多
Domain structure often has significant influences on both piezoelectric properties and piezoelectric temperature stability of a ferroelectric ceramic.In-depth studies on the characters of domain structure should be he...Domain structure often has significant influences on both piezoelectric properties and piezoelectric temperature stability of a ferroelectric ceramic.In-depth studies on the characters of domain structure should be helpful for the better understanding of piezoelectric performance.In this work,the evolution of domain structure in large-d_(33)0.96(K_(0.48)Na_(0.52))(Nb_(0.96)Sb_(0.04))O_(3)-0.04(Bi_(0.50)Na_(0.50))ZrO_(3) ceramics with poling and temperature was systematically investigated via comparing the various domain patterns that are obtained by acid-etching.It was found that domain structure changes greatly upon poling and varies largely with temperature.Complex domain patterns consisting of long narrow parallel stripes or herringbone structure separated by 180°domain boundaries are observed in the unpoled ceramics at room temperature.Domain patterns become less complicated upon poling,due to the collective polarization reversals of parallel-stripe domain clusters and banded fine-stripe domain segments.Parallel stripes and herringbone bands become much wider upon poling,as some narrow stripes and herringbone bands coalesce into broad ones,respectively.Hierarchical domain structure is commonly seen in the domain patterns acid-etched at room temperature,but is less frequently recognized at elevated temperatures.Schematic models of domain configurations were proposed to explain the domain structure and its evolution with poling.展开更多
After field cooling(FC)alternating current poling(ACP),we investigated the dielectric and piezoelectric properties of[001]_(pc)-oriented 0.24Pb(In_(1/2)Nb_(1/2))O_(3)(PIN)-0.46Pb(Mg_(1/3)Nb_(2/3))O_(3)(PMN)-0.30PbTiO3...After field cooling(FC)alternating current poling(ACP),we investigated the dielectric and piezoelectric properties of[001]_(pc)-oriented 0.24Pb(In_(1/2)Nb_(1/2))O_(3)(PIN)-0.46Pb(Mg_(1/3)Nb_(2/3))O_(3)(PMN)-0.30PbTiO3(PT)(PIMN-0.30PT)single crystals(SCs),which were manufactured by continuous-feeding Bridgman(CF BM)within morphotropic phase boundary(MPB)region.By ACP with 4 kVrms/cm from 100 to 70℃,the PIMN-0.30PT SC attained high dielectric permittivity of 8330,piezoelectric coefficient(d_(33))of 2750 pC/N,bar mode electromechanical coupling factorκ_(33)of 0.96 with higher phase change temperature(T_(pc))of 103℃,and high Curie temperature(7c)of 180℃.These values are the highest ever reported as PIMN-xPT SC system with Tpc>100℃.The enhancement of these properties is attributed to the induced low symmetry multi-phase supported by phase analysis.This work indicates that FC ACP is a smart and promising method to enhance piezoelectric properties of relaxor-PT ferroelectric SCs including PIMN-xPT,and provides a route to a wide range of piezoelectric device applications.展开更多
The temporal pole(TP),one of the most expanded cortical regions in humans relative to other primates,plays a crucial role in human language processing.It is also one of the most structurally and functionally asymmetri...The temporal pole(TP),one of the most expanded cortical regions in humans relative to other primates,plays a crucial role in human language processing.It is also one of the most structurally and functionally asymmetric regions.However,whether the functional architecture of the TP is shared by humans and macaques is an open question.We used spectral clustering algorithms to define a cross-species fine-grained TP atlas with different anatomical connectivity patterns.We identified three similar subregions,two ventral and one dorsal,within the TP in both humans and macaques.The parcellation scheme for the TP was validated using functional gradient mapping,anatomical connectivity and resting-state functional connectivity pattern analysis,and functional characterization.Furthermore,in conjunction with the Allen Human Brain Atlas,we revealed the molecular basis for the functional connectivity patterns of each human TP subregion.In addition,we compared the hemispheric asymmetry in mean gray matter volume,anatomical connectivity fingerprints,and whole brain functional connectivity patterns to reveal the evolutionary differences in the TP and found different asymmetric patterns between humans and macaques.In conclusion,our findings reveal that the asymmetry in structure and connectivity may underpin the hemispheric functional specialization of the brain and provide a novel insight into understanding the evolutionary origin of the TP.展开更多
Yiwu merchants ride a winter sports boom as“Made in China”winter gear heats up the global economy.YIWU,located in east China’s Zhejiang Province,is globally renowned as a hub for small commodities.This winter,its s...Yiwu merchants ride a winter sports boom as“Made in China”winter gear heats up the global economy.YIWU,located in east China’s Zhejiang Province,is globally renowned as a hub for small commodities.This winter,its snow and ice sports products are generating a surge in business.Products such as snowboards,ski goggles,and ski poles are drawing an increasing number of merchants worldwide for purchases.展开更多
文摘Two different poling techniques-corona poling and contact poling in the backdrop of electro-optic （EO） polymer modulators are compared. A 3-layer structure EO polymer modulator is prepared for the poling. The poling setups and procedures of these two different methods are given. It is found that a well-controlled precure step is very critical, otherwise it will result in either lower poling efficiency or damaged film. Experimental results show that contact poling does not create severe surface damage as corona poling and poling voltage is much lower, but corona poling provides higher EO effect than contact poling. Besides, contact poling can provide poling size as large as the substrate size.
基金financially supported by the National Key Research and Development Program of China(No.2018YFC0308603)the Pilot Technology for Chinese Academy of Sciences(No.XDA2203003)the National Natural Science Foundation of China(Nos.51972321 and 51879269)。
文摘High piezoelectric properties and superior thermal stability are both important indicators of piezoelectric ceramics serving at high temperature.However,since these properties are usually mutually exclusive,high performance and superior thermal stability are hard to achieve simultaneously.Here we report that a high piezoelectricity(d_(33)∼562 pC/N)and superior thermal stability(the variation is within 7%from 20 to 330℃)were both achieved in 0.4 mol%ZnO-doped 0.02Pb(Sb_(1/2)Nb_(1/2))-0.51PbZrO_(3)-0.47PbTiO_(3) by high-temperature poling.Compared with traditional poling method,high-temperature poling method forms a small-sized and highly oriented domain structure,which can effectively improve the piezoelectric and dielectric properties of piezoelectric ceramics.At the same time,the enhanced pinning effect of defect ions and stabilized domain structure due to high-temperature poling also contribute to the superior temperature stability of the piezoelectric and dielectric properties.This work provides an effective method for designing piezoelectric materials with high performance and good temperature stability for high temperature sensor applications.
文摘In this paper, the poling properties of (PS)O-DCV, a derivative of poly (p-hydroxystyrene ), was reported. The investigations showed that the thermochromism correction, which was neglected in the literatures, should be considered in the measurements of order parameter of poled films with electrochromism technique Here, another linear optical method, IR and polarized IR spectra for characterizing of poled films was suggested first time. The bulk second nonlinear optical coefficient d_(33) of poled films could be estimated by measured order parameter semi-qualitatively.
基金supported by ONR(N00014-05-1-0338)NSF(DMR-0907580)
文摘We studied cycle time （0.01-10 s with triangular input waves） and poling history （continuous versus fresh poling） dependent electric energy storage and discharge behaviors in poly（vinylidene fluoride-co-hexafluoropropylene） [P（VDF- HFP）] films using the electric displacement -- the electric field （D-E） hysteresis loop measurements. Since the permanent dipoles in PVDF are orientational in nature, it is generally considered that both charging and discharging processes should be time and poling history dependent. Intriguingly, our experimental results showed that the charging process depended heavily on the cycle time and the prior poling history, and thus the D-E hysteresis loops had different shapes accordingly. However, the discharged energy density did not change no matter how the D-E loop shape varied due to different measurements. This experimental result could be explained in terms of reversible and irreversible polarizations. The reversible polarization could be charged and discharged fairly quickly （〈 5 ms for each process）, while the irreversible polarization depended heavily on the poling time and the prior poling history. This study suggests that it is only meaningful to compare the discharged energy density for PVDF and its copolymer films when different cycle times and poling histories are used.
文摘In attempts to fabricate thermally stable second-order nonlinear polymer thin films, we have investigated the second harmonic generation (SHG) from both nonlinear polymer and vip-host thin films. We have also investigated the role of capping on the SHG, temporal stability and relaxation of dipole alignment. Corona poling techniques were employed to orient the dopants into the noncentrosymmetric structure required to obtain the SHG. The effect of capping with a polymeric encapsulant below the glass transition temperature of the polymers on the unpoled and corona poled thin films was studied. Capping of the nonlinear polymer and vip host thin films have resulted in high SHG with good temporal stability. SHG signal falls drastically during the first 8 days after poling while no further significant decay in SHG signal was observed after about 33 days. Our investigations have identified the characteristics required for a good encapsulant on a non-con-ductive surface.
基金supported by the National Natural Science Foundation of China(Nos.62275042 and U20A20165)the Sichuan Province Key Research&Development Cooperation Project(No.2024YFHZ0348)Huawei Technologies Co.,Ltd.and Tianfu Jiangxi Lab for their financial support。
文摘Electric field poling of electro-optic polymer(EOP)in hybrid waveguides is highly challenging due to the discontinuity in electric field distribution,which leads to a low Pockels electro-optic(EO)coefficient or dielectric breakdown.We propose the segmented poling technique in Si_(3)N_(4)/EOP hybrid waveguides to address this challenge.Dipolar chromophores near an electrode interface first align with a weak poling electric field,and then a strong field is applied for the chromophore alignment near the waveguide interface.This technique effectively avoids dielectric breakdown,and the tuning efficiency of the EO Mach-Zender interferometer(MZI)filters is improved from 31.7 pm/V to higher than 50 pm/V,with a highest Pockels coefficient of 114 pm/V.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 59790050-3 and 29704009) and the National "863" Program (Grant No. 863-715-002-0120).
文摘The high Tg polyimide embedded with a novel imidazol-typed chromophore 2-[5-(4-nitrostilbenyl)thienyl]-4,S-di(4-aniinophenyl)imidazole (NSTDAPI) was prepared using the 'simultaneous poling and polymerization' technique. The glass transition temperature (Fg) is 304℃ and the initial decomposition temperature (Td) is 330℃. The in-situ second harmonic generation (in-situ SHG) measurement was performed to study its poling behavior and the stability of the poling-induced orientation. The nonlinear optical (NLO) coefficient d33 of poled polyimide film is 32.2 pm/V at 1064 nm fundamental wavelength. The SHG signal of the poled polymer film was quite stable below 200℃, and then began to decay rapidly above 220℃. The half-decay temperature of dipole orientation for the film is 250℃.
文摘Alternating current poling(ACP)in air by changing poling temperature(70e130℃)and voltages(2e6 kVrms/cm)on pseudo-ternary 0.24 Pb(In_(1/2)Nb_(1/2))O_(3)-0.46 Pb(Mg1/3Nb_(2/3))O3-0.30PbTiO_(3)(PIMN-0.30PT)single crystals(SCs)manufactured by continuous-feeding Bridgman(CF BM)method was investigated.Free dielectric permittivity(εT 33/ε0)and piezoelectric constant(d33)were improved to be 7000 and 2340 pC/N,which were 29%higher than those of direct current poling(DCP)at 90℃ with 4 kV/cm(εT 33/ε0=5440,d_(33)=1810 pC/N).However,phase change temperature(Tpc)decreased from 94℃ to 78℃ as opposite results reported by other groups.We demonstrated that the high temperature(HT)ACP improved piezoelectric performance of CF BM SCs,however,the Tpc were different from other crystal growth method.The well-designed ACP process was a promising method for mass production not only to enhance the electrical properties for the pseudo-ternary SCs but also reduce the risk of breakdown and realizes organic solvent-free poling process.
基金supported by the National Natural Science Foundation of China(52072028 and 52032007)the National Key Research and Development Program(2022YFB3807400).
文摘BiFeO_(3)-BaTiO_(3) based ceramics are considered to be the most promising lead-free piezoelectric ceramics due to their large piezoelectric response and high Curie temperature.Since the piezoelectric response of piezoelectric ceramics just appears after poling engineering,in this work,the domain evolution and microscopic piezoresponse were observed in-situ using piezoresponse force microscopy(PFM)and switching spectroscopy piezoresponse force microscopy(SS-PFM),which can effectively study the local switching characteristics of ferroelectric materials especially at the nanoscale.The new domain nucleation preferentially forms at the boundary of the relative polarization region and expands laterally with the increase of bias voltage and temperature.The maximum piezoresponse(Rs),remnant piezoresponse(Rrem),maximum displacement(Dmax)and negative displacement(Dneg)at 45 V and 120C reach 122,69,127 pm and 75 pm,respectively.Due to the distinct effect of poling engineering in full domain switching,the corresponding d33 at 50 kV/cm and 120C reaches a maximum of 205 pC/N,which is nearly twice as high as that at room temperature.Studying the evolution of ferroelectric domains in the poling engineering of BiFeO_(3)-BaTiO_(3)ceramics provides an insight into the relationship between domain structure and piezoelectric response,which has implications for other piezoelectric ceramics as well.
文摘The effects of alternating current poling(ACP)at 80℃on electrical properties of[001]-oriented 0.72 Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.28PbTiO_(3)(PMN-28PT)single crystals(SCs)have been investigated.The square-wave ACP SCs poled at high voltage(HV,5 kV_(rms)/cm)occasionally showed large fluctuations and low opposite values of piezoelectric coefficient(d_(33)=±1370 pC/N)in one plate.This revealed spuriousmode vibrations(SMV)of impedance spectrum.However,after depolarizing and repolarizing the sample with a sine-wave ACP at low voltage(LV,3.5 kV_(rms)/cm),the d_(33) enhanced to be 1720 pC/N(+26%)and did not exhibit large fluctuation or opposite values in one plate any more.The impedance spectrum became clean and the abnormal SMV disappeared.We proposed four possible mechanisms of the SMV,and speculate that the main cause maybe by macro-scale sub-domain structure and/or phase change in the main domain structure and/or phase in the SC plate due to the specific poling conditions not eternal mechanical damage of PMN-PT SCs.This study will be useful to realize a high d_(33) and improve other properties of PMN-PT ACP SC ultrasonic transducers without any SMV for high-frequency medical imaging equipment.
文摘Based on the experimental results, three basic conclusions are summarized for the thermal/electric-field poling (TEFP) silica materials, with which the second-order nonlinear optical coefficient in the bulk silica glass after TEFP is calculated, and relationships between the coefficient and the applied voltage V 0 in the poling process and the thickness of the nonlinear layer created from the poling are obtained. Theoretical results show that the second-order susceptibility χ(2) and the second-harmonic efficiency η in the poled bulk glass are proportional to √V 0 and V 0 2 , respectively; χ(2)～0.2?1.6 pm/V for the bulk glass after the typical TEFP; χ(2) decreases with an increase in the poling time after the TEFP silica glass approximately reaches the steady state. Theoretical results are well consistent with the experimental reports.
文摘Conductive ferroelectric domain walls have attracted increasing research interest in the field of nanoelectronics,and the fabrication technique for such domain walls is vital.In this study,we investigated in detail the fabrication of conductive domain walls in x-cut congruent thin-film lithium niobate(TFLN)using an electrical-field poling technique.The ferroelectric domain structures can be controlled through the applied electrical field and applied pulse numbers,and the domain inversion process is related to the conduction characteristics of the domain walls.The domain structures in TFLN are revealed using confocal second-harmonic microscopy and piezoresponse force microscopy.The results provide further directions for the development and application of conductive domain walls in TFLN.
基金financially supported by the National Natural Science Foundation of China(Grant No.51972196)Shandong Provincial Natural Science Foundation,China(Grants No.ZR2019MEM07).
文摘Domain structure often has significant influences on both piezoelectric properties and piezoelectric temperature stability of a ferroelectric ceramic.In-depth studies on the characters of domain structure should be helpful for the better understanding of piezoelectric performance.In this work,the evolution of domain structure in large-d_(33)0.96(K_(0.48)Na_(0.52))(Nb_(0.96)Sb_(0.04))O_(3)-0.04(Bi_(0.50)Na_(0.50))ZrO_(3) ceramics with poling and temperature was systematically investigated via comparing the various domain patterns that are obtained by acid-etching.It was found that domain structure changes greatly upon poling and varies largely with temperature.Complex domain patterns consisting of long narrow parallel stripes or herringbone structure separated by 180°domain boundaries are observed in the unpoled ceramics at room temperature.Domain patterns become less complicated upon poling,due to the collective polarization reversals of parallel-stripe domain clusters and banded fine-stripe domain segments.Parallel stripes and herringbone bands become much wider upon poling,as some narrow stripes and herringbone bands coalesce into broad ones,respectively.Hierarchical domain structure is commonly seen in the domain patterns acid-etched at room temperature,but is less frequently recognized at elevated temperatures.Schematic models of domain configurations were proposed to explain the domain structure and its evolution with poling.
基金supported by the Murata Science Foundation Japan(H31JOJI022).
文摘After field cooling(FC)alternating current poling(ACP),we investigated the dielectric and piezoelectric properties of[001]_(pc)-oriented 0.24Pb(In_(1/2)Nb_(1/2))O_(3)(PIN)-0.46Pb(Mg_(1/3)Nb_(2/3))O_(3)(PMN)-0.30PbTiO3(PT)(PIMN-0.30PT)single crystals(SCs),which were manufactured by continuous-feeding Bridgman(CF BM)within morphotropic phase boundary(MPB)region.By ACP with 4 kVrms/cm from 100 to 70℃,the PIMN-0.30PT SC attained high dielectric permittivity of 8330,piezoelectric coefficient(d_(33))of 2750 pC/N,bar mode electromechanical coupling factorκ_(33)of 0.96 with higher phase change temperature(T_(pc))of 103℃,and high Curie temperature(7c)of 180℃.These values are the highest ever reported as PIMN-xPT SC system with Tpc>100℃.The enhancement of these properties is attributed to the induced low symmetry multi-phase supported by phase analysis.This work indicates that FC ACP is a smart and promising method to enhance piezoelectric properties of relaxor-PT ferroelectric SCs including PIMN-xPT,and provides a route to a wide range of piezoelectric device applications.
基金supported by the Yunnan Fundamental Research Projects(202501AV070005 and 202201BE070001-004).
文摘The temporal pole(TP),one of the most expanded cortical regions in humans relative to other primates,plays a crucial role in human language processing.It is also one of the most structurally and functionally asymmetric regions.However,whether the functional architecture of the TP is shared by humans and macaques is an open question.We used spectral clustering algorithms to define a cross-species fine-grained TP atlas with different anatomical connectivity patterns.We identified three similar subregions,two ventral and one dorsal,within the TP in both humans and macaques.The parcellation scheme for the TP was validated using functional gradient mapping,anatomical connectivity and resting-state functional connectivity pattern analysis,and functional characterization.Furthermore,in conjunction with the Allen Human Brain Atlas,we revealed the molecular basis for the functional connectivity patterns of each human TP subregion.In addition,we compared the hemispheric asymmetry in mean gray matter volume,anatomical connectivity fingerprints,and whole brain functional connectivity patterns to reveal the evolutionary differences in the TP and found different asymmetric patterns between humans and macaques.In conclusion,our findings reveal that the asymmetry in structure and connectivity may underpin the hemispheric functional specialization of the brain and provide a novel insight into understanding the evolutionary origin of the TP.
文摘Yiwu merchants ride a winter sports boom as“Made in China”winter gear heats up the global economy.YIWU,located in east China’s Zhejiang Province,is globally renowned as a hub for small commodities.This winter,its snow and ice sports products are generating a surge in business.Products such as snowboards,ski goggles,and ski poles are drawing an increasing number of merchants worldwide for purchases.
