The strong electro mechanical coupling exhibited by the ferroelectric materials is the remarkable feature of these materials. Therefore, they find applications in sensors, actuators for producing ultrasonics and micro...The strong electro mechanical coupling exhibited by the ferroelectric materials is the remarkable feature of these materials. Therefore, they find applications in sensors, actuators for producing ultrasonics and micro positioning. The material dichloridoglycine zinc dihydrate is a centrosymmetric ferroelectric crystal. In the present study, this crystal has been grown from a mixture of glycine and zinc chloride. The dielectric constant and the dielectric loss of the grown crystal were studied as a function of frequency and temperature, and the corresponding relaxation time (τ), relaxation frequency (Fr) and the activation energy have been calculated. The ferroelectric property of the crystal has been confirmed by dielectric studies. The ferroelectric characteristics of the crystal have been studied and reported.展开更多
Investigations on the interconnection between the polarization rotation and crack propagation are performed for [110J-oriented 74Pb（Mg1/3Nb2/3）O3- 26PbTiO3 relaxor ferroelectric single crystal under electric loading...Investigations on the interconnection between the polarization rotation and crack propagation are performed for [110J-oriented 74Pb（Mg1/3Nb2/3）O3- 26PbTiO3 relaxor ferroelectric single crystal under electric loadings along [001] direction. The crystal is of predominantly monoclinic MA phase with scatter dis- tributed rhombohedral （R） phase under a moderate poling field of 900 V/mm in [00l] direction. With magnitude of 800 V/ram, a through thickness crack is initi- ated near the electrode by electric cycling. Static electric loadings is then imposed to the single crystal. As the applied static electric field increases, domain switch- ing in the monoclinic MA phase and phase transition from MA to R phase occur near the crack. The results indicate that the crack features a conducting one. Whether domain switching or phase transition occurs depends on the intensity of the electric field component that is perpendicular to the applied electric field.展开更多
Qualification of polarization can be realized either on a macroscopic scale as an average property by P-E hysteresis measurements or on a nano/micro scale by piezoelectric force microscopy,transmission electron micros...Qualification of polarization can be realized either on a macroscopic scale as an average property by P-E hysteresis measurements or on a nano/micro scale by piezoelectric force microscopy,transmission electron microscopy,scanning electron microscopy,and so on.However,visualization and qualification of polarization distribution in the micron to millimeter scale is still a challenge.Polarizing light microscopy(PLM)is often used in the study of ferroelectric domain structures mainly for domain patterns.A phe-nomenon called“chromatic polarization”has been observed in transparent ferroelectric crystals by using a crossed-PLM system viewed with white light,which contains rich information about local polariza-tion distribution.In this study,an automatic full-angle light intensity detection(AFALID)algorithm com-bined with colorimetry is developed to analyze the distribution of nonuniform local spontaneous polar-ization distribution in transparent ferroelectric single crystals.Temperature-dependent spontaneous po-larizations from the color analysis for PMN-0.36PT single crystals with single tetragonal domain state are in good coincidence with those extracted from temperature-dependent hysteresis loops and pyroelectric current measurements.We further apply this method to quantify the nonuniform domain distributions with nano-indentations.This non-contact and non-destructive characterization can provide fast and au-tomatic detection of polarization distributions in ferroelectric materials.展开更多
We have derived a general formula for sensitivity optimization of gravimetric sensors and have used it to design a high sensitivity gravimetric sensor using unidirectional carbon fiber epoxy composite （CFEC） wavegui...We have derived a general formula for sensitivity optimization of gravimetric sensors and have used it to design a high sensitivity gravimetric sensor using unidirectional carbon fiber epoxy composite （CFEC） waveguide layer on （1 -x）Pb（Znl/3Nbz/3）O3-xPbTiO3 （PZN-xPT） single crystal substrate with the carbon fibers parallel to the xj and x2 axes, respectively. The normalized maximum sensitivity （｜sfm｜λ）max exhibits an increasing tendency with the decrease of （h/λ）opt and the maximum sensitivity （｜sfm｜λ）max increases with the elastic constant c6E6 of the piezoelectric substrate material. For the CFEC/[011]c poled PZN-7%PT single crystal sensor configuration, with the carbon fibers parallel to the xa axis at λ = 24 ktm, the maximum sensitivity ｜sfm｜max can reach as high as 1156 cmZ/g, which is about three times that of a traditional SiO2/ST quartz structure gravimetric sensor. The better design selection is to have the carbon fibers parallel to the direction of propagation of Love wave in order to obtain the best sensitivity.展开更多
To further enhance the property of piezoelectric materials is of great significance to improve the overall performance of electro-mechanical devices.Here in this work,we propose a thermal annealing and high temperatur...To further enhance the property of piezoelectric materials is of great significance to improve the overall performance of electro-mechanical devices.Here in this work,we propose a thermal annealing and high temperature poling approach to achieve significantly enhanced piezoelectricity in Pb(In_(1/2)Nb_(1/2))O_(3)single bondPb(Mg_(1/3)Nb_(2/3))O_(3)single bondPbTiO_(3)(PIN-PMN-PT)crystals with a morphotropic phase boundary(MPB)composition.The main idea of our approach is to realize a more sufficiently polarized crystal via active manipulation of defects and orientation of defect polarization.Manipulation of defect dipoles by the high temperature poling is proved by the piezo-response force microscopy.Finally,a d_(33)of 3300 pC/N and a SE of 0.25%are obtained,nearly 60%higher than that of conventionally poled crystals.Moreover,such a boosting of piezoelectric property is obtained under a maintained Curie temperature.Our research not only reveals the active control of defect dipole via modified poling method in the PIN-PMN-PT crystal,but also provides a feasible strategy to further improve the property of piezoelectric materials.展开更多
Our progress in the growth of ternary system Pb(In_(1/2)Nb_(1/2))O_(3)–Pb(Mg_(1/3)Nb_(2/3))O_(3)–PbTiO_(3)(PIMNT)crystals and reviews on the possible developing trends in the piezoelectric crystals are presented.Lar...Our progress in the growth of ternary system Pb(In_(1/2)Nb_(1/2))O_(3)–Pb(Mg_(1/3)Nb_(2/3))O_(3)–PbTiO_(3)(PIMNT)crystals and reviews on the possible developing trends in the piezoelectric crystals are presented.Large PIMNT crystals with 3 inches in diameter have been grown by using a modified Bridgman method.Meanwhile,Mn-doped PIMNT crystals have also been obtained.PIMNT crystals exhibit Curie temperature Tc190C,rhombohedral–tetragonal phase transition temperature Trt>100℃ and coercive field Ec5:0–7.0 kV/cm on(001)cuts.Meanwhile,higher piezoelectric constant d_(32)-1500–2200 pC/N,d_(15)4000–6000 pC/N and coercive field E_(c)-7:0–9.0 kV/cm have been achieved on(110)cuts.The development trends of relaxor-based ferroelectric crystals are suggested to grow novel crystals with high rhombohedral–tetragonal phase transition temperature T_(rt)>150-160℃ and/or high coercive field Ec and mechanical quality factor Q_(m),to promote growth efficiency of PIMNT crystals and to create new growth methods fitting for the growth of metastable or instable crystals.展开更多
Relaxor ferroelectric single crystals PMNT with the size of φ40 mm×80 mm have been grown by a modified Bridgman method and their ferroelectric and piezoelectric properties have been characterized. The properties...Relaxor ferroelectric single crystals PMNT with the size of φ40 mm×80 mm have been grown by a modified Bridgman method and their ferroelectric and piezoelectric properties have been characterized. The properties varied with the compositions and cut types. On the (001) cut, PMNT76/24 single crystals exhibited a dielectric constant ε of about 3 400, a dielectric loss of tanδ 【0.7%, a piezoelectric constant d33 of 980 pC/N, an electromechanical coupling factor kt of 0.55 and Tc of about 110℃. whereas the properties of PMNT67/33 single crystals on (001) cut were betler: e of about 5 300, tan5 【0.6%, d33 up to 3 000 pC/N, kt 0.64, K33 0.93 and Tc of about 150℃. The piezoelectric properties on other cuts such as (110) and (111) were much lower than those on the (001) cut. The rhombohedral PMNT crystals grown by this method showed more excellent piezoelectric properties than those grown by high temperature solution method and higher value of kt than the rhombohedral PZNT single crystals. it has also展开更多
High-performance relaxor ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 have been grown successfully by a modified Bridgman method. They have the size of 25×25×50 mm3 and are of pure perovskite phases...High-performance relaxor ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 have been grown successfully by a modified Bridgman method. They have the size of 25×25×50 mm3 and are of pure perovskite phases with tetragonal or rhombohedral structures. Their {001} faces appear dominantly, which can be interpreted by the model of an-ionic coordination polyhedral growth units. Main macro defects observed under optical microscopes and SEM can be reduced or removed by improving growth parameters after understanding their formation mechanism. 71°or 109°macrodomains in rhombohedral PMNT 76/24 crystals and 90°macrodomains in tetragonal PMNT 65/35 crystals have been observed by optical microscopes. It has been found that the transition from microdomains to macrodomains can be induced by compositions. Both the imaging mechanism of non-180° domains and the relation between domain configurations and ferroelectric phase transition have been analyzed.展开更多
The features of the single crystals 0.76PMN-0.24PT in dielectric, ferroelectric, pyroelectric properties and domain structures indicate that they are located between typical ferroelectrics and normal ones. The unpoled...The features of the single crystals 0.76PMN-0.24PT in dielectric, ferroelectric, pyroelectric properties and domain structures indicate that they are located between typical ferroelectrics and normal ones. The unpoled crystals present a transitional domain configuration between microdomains and typical macrodomains while the crystals on (001) cuts undergo field-induced phase transition under poling, showing two special temperature points Td and Tm during the succedent heating procedure. The dielectric constant starts to decrease drastically at Td during cooling, or the transformation from induced macrodomain to transitional domain takes place at Td during heating. Ferroelectric-paraelectric phase transition or depolarization continues within the whole temperature range of Td-Tm, where ferroelectric phase in the form of transitional macrodomains coexists with paraelectric phase. Then the crystals macroscopically transoform into paraelectric phase containing ferroelectric microdomains at a temperature展开更多
This collection presents 505 papers on ferroelectricity in single crystals,ceramics and polymers in which pointed or elliptical hysteresis loops would testify to their ferroelectric properties.In some papers,the autho...This collection presents 505 papers on ferroelectricity in single crystals,ceramics and polymers in which pointed or elliptical hysteresis loops would testify to their ferroelectric properties.In some papers,the authors ensure that ferroelectricity can occur even in materials that do not have a polar axis of symmetry.展开更多
Single crystals of(1x) Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PMN-xPT)near their morphotropic phase boundaries(MPBs)are under extensive investigations for their extraordinary high dielectric and piezoelectric behavior.Ap...Single crystals of(1x) Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PMN-xPT)near their morphotropic phase boundaries(MPBs)are under extensive investigations for their extraordinary high dielectric and piezoelectric behavior.Applications of those single crystals facilitated the breakthrough in ultrasonic transducer materials and devices.Ferroelectric materials are known to be fragile which often leads to various reliability failures in applications involving electric loadings.In a mechanical sense,the failure modes concern the fracture under an intensive electric field,and the fatigue crack propagation under an alternating electric field.In an electrical sense,the failure is exhibited by degenerated hysteresis loop by shrinking the remnant polarization and expanding the coercive field.All these modes degrade the performance for ferroelectric devices.As a departure from the tetragonal TÞferroelectric materials,exemplified by BaTiO_(3) and Pb(ZrTi)O_(3),the domain structures of PMN-PT around the MPB are versatile and intricate,depending sensitively on the composition variation,orientation and previous loading history.In this review,the attention is mainly focused on three aspects.First,the phase fragility and multiphase coexistence are presented for both[100]-and[101]-oriented PMN-PT single crystals.Second,investigations on electric field-induced fatigue crack propagation are described,along with the orientation effect on the crack propagation behavior.Third,the inverse effects of the phase transition and fatigue crack growth on the polarization behavior,or the interaction between the mechanical and electrical degradations will be elucidated.The review aims for better understanding the underlying mechanism for the ultrahigh performance of the PMN-PT single crystals,to bridge the studies of ferroelectric materials from the mechanical and electrical senses,as well as to evaluate the reliability of PMN-PT single crystals under device applications.展开更多
A two-dimensional vector hydrophone was developed utilizing the PMN-PT relaxor ferroelectric single crystal,which is composed of a dual-axis piezoelectric composite flexural beam accelerometer and PZT-5 piezoelectric ...A two-dimensional vector hydrophone was developed utilizing the PMN-PT relaxor ferroelectric single crystal,which is composed of a dual-axis piezoelectric composite flexural beam accelerometer and PZT-5 piezoelectric ceramic rings.Based on the principle of elastic mechanics and underwater particle velocity measurement,the receiving voltage sensitivity of the flexural beam vector hydrophone is derived.The influence of stress distribution in the flexural beam on the performance of hydrophones is analyzed,and the match between PMNPT single crystal cells and the structure of flexural beam is studied.The tested results indicate that the PMN-PT hydrophone presents an 11 dB increase in sensitivity and a 3 dB decrease in self-noise than the PZT-5 one.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
The piezoresponse behavior dependence of the Pb(Mg1/3Nb2/3)O3-30%PbTiO3 single crystal on the vacuum degree has been investigated by scanning force microscopy in the piezoresponse mode under high vacuum. Unusual piezo...The piezoresponse behavior dependence of the Pb(Mg1/3Nb2/3)O3-30%PbTiO3 single crystal on the vacuum degree has been investigated by scanning force microscopy in the piezoresponse mode under high vacuum. Unusual piezo- response behavior related to the screening charges compensation mechanism is observed on the (111) crystal face. The significant piezoresponse degradation behavior with low piezoresponse signal under high vacuum is attributed to the instability of the polarization state due to the insufficient compensation of the intrinsic screening charges for the polarization charges in PMN-30%PT single crystal. In contrast, the remarkable domain contrast of the sample at ambient pressure is owing to the dominant surface screening charges deriving from surface adsorption, which plays an important role in determining the stability of the domain behavior and in achieving the optimal properties.展开更多
文摘The strong electro mechanical coupling exhibited by the ferroelectric materials is the remarkable feature of these materials. Therefore, they find applications in sensors, actuators for producing ultrasonics and micro positioning. The material dichloridoglycine zinc dihydrate is a centrosymmetric ferroelectric crystal. In the present study, this crystal has been grown from a mixture of glycine and zinc chloride. The dielectric constant and the dielectric loss of the grown crystal were studied as a function of frequency and temperature, and the corresponding relaxation time (τ), relaxation frequency (Fr) and the activation energy have been calculated. The ferroelectric property of the crystal has been confirmed by dielectric studies. The ferroelectric characteristics of the crystal have been studied and reported.
基金supported by the National Natural Science Foundation of China(11272174)
文摘Investigations on the interconnection between the polarization rotation and crack propagation are performed for [110J-oriented 74Pb（Mg1/3Nb2/3）O3- 26PbTiO3 relaxor ferroelectric single crystal under electric loadings along [001] direction. The crystal is of predominantly monoclinic MA phase with scatter dis- tributed rhombohedral （R） phase under a moderate poling field of 900 V/mm in [00l] direction. With magnitude of 800 V/ram, a through thickness crack is initi- ated near the electrode by electric cycling. Static electric loadings is then imposed to the single crystal. As the applied static electric field increases, domain switch- ing in the monoclinic MA phase and phase transition from MA to R phase occur near the crack. The results indicate that the crack features a conducting one. Whether domain switching or phase transition occurs depends on the intensity of the electric field component that is perpendicular to the applied electric field.
基金This work is financially supported by the National Key Re-search and Development Program of China(No.2021YFF0501001)the Heilongjiang Provincial Natural Science Foundation of China(No.LH2020A006)the Open Fund of Key Laboratory for In-telligent Nano Materials and Devices of the Ministry of Education NJ2022002(No.INMD-2022M08).
文摘Qualification of polarization can be realized either on a macroscopic scale as an average property by P-E hysteresis measurements or on a nano/micro scale by piezoelectric force microscopy,transmission electron microscopy,scanning electron microscopy,and so on.However,visualization and qualification of polarization distribution in the micron to millimeter scale is still a challenge.Polarizing light microscopy(PLM)is often used in the study of ferroelectric domain structures mainly for domain patterns.A phe-nomenon called“chromatic polarization”has been observed in transparent ferroelectric crystals by using a crossed-PLM system viewed with white light,which contains rich information about local polariza-tion distribution.In this study,an automatic full-angle light intensity detection(AFALID)algorithm com-bined with colorimetry is developed to analyze the distribution of nonuniform local spontaneous polar-ization distribution in transparent ferroelectric single crystals.Temperature-dependent spontaneous po-larizations from the color analysis for PMN-0.36PT single crystals with single tetragonal domain state are in good coincidence with those extracted from temperature-dependent hysteresis loops and pyroelectric current measurements.We further apply this method to quantify the nonuniform domain distributions with nano-indentations.This non-contact and non-destructive characterization can provide fast and au-tomatic detection of polarization distributions in ferroelectric materials.
基金supported by the National Basic Research Program of China(Grant No.2013CB632900)
文摘We have derived a general formula for sensitivity optimization of gravimetric sensors and have used it to design a high sensitivity gravimetric sensor using unidirectional carbon fiber epoxy composite （CFEC） waveguide layer on （1 -x）Pb（Znl/3Nbz/3）O3-xPbTiO3 （PZN-xPT） single crystal substrate with the carbon fibers parallel to the xj and x2 axes, respectively. The normalized maximum sensitivity （｜sfm｜λ）max exhibits an increasing tendency with the decrease of （h/λ）opt and the maximum sensitivity （｜sfm｜λ）max increases with the elastic constant c6E6 of the piezoelectric substrate material. For the CFEC/[011]c poled PZN-7%PT single crystal sensor configuration, with the carbon fibers parallel to the xa axis at λ = 24 ktm, the maximum sensitivity ｜sfm｜max can reach as high as 1156 cmZ/g, which is about three times that of a traditional SiO2/ST quartz structure gravimetric sensor. The better design selection is to have the carbon fibers parallel to the direction of propagation of Love wave in order to obtain the best sensitivity.
基金This work is supported by the National Nature Science Foundation of China(Grant Nos.52102143,51772239,62001369 and 51761145024)Shaanxi province project(2017ktpt-21 and 2018TD-024)Jiangxi Technological Innovation Guidance Science and Technology Plan(Grant No.S20212BDH80017)。
文摘To further enhance the property of piezoelectric materials is of great significance to improve the overall performance of electro-mechanical devices.Here in this work,we propose a thermal annealing and high temperature poling approach to achieve significantly enhanced piezoelectricity in Pb(In_(1/2)Nb_(1/2))O_(3)single bondPb(Mg_(1/3)Nb_(2/3))O_(3)single bondPbTiO_(3)(PIN-PMN-PT)crystals with a morphotropic phase boundary(MPB)composition.The main idea of our approach is to realize a more sufficiently polarized crystal via active manipulation of defects and orientation of defect polarization.Manipulation of defect dipoles by the high temperature poling is proved by the piezo-response force microscopy.Finally,a d_(33)of 3300 pC/N and a SE of 0.25%are obtained,nearly 60%higher than that of conventionally poled crystals.Moreover,such a boosting of piezoelectric property is obtained under a maintained Curie temperature.Our research not only reveals the active control of defect dipole via modified poling method in the PIN-PMN-PT crystal,but also provides a feasible strategy to further improve the property of piezoelectric materials.
基金supported by the national science and technology pillar program of the twelfth five-year of China under Grant No.2012BAI13B01.
文摘Our progress in the growth of ternary system Pb(In_(1/2)Nb_(1/2))O_(3)–Pb(Mg_(1/3)Nb_(2/3))O_(3)–PbTiO_(3)(PIMNT)crystals and reviews on the possible developing trends in the piezoelectric crystals are presented.Large PIMNT crystals with 3 inches in diameter have been grown by using a modified Bridgman method.Meanwhile,Mn-doped PIMNT crystals have also been obtained.PIMNT crystals exhibit Curie temperature Tc190C,rhombohedral–tetragonal phase transition temperature Trt>100℃ and coercive field Ec5:0–7.0 kV/cm on(001)cuts.Meanwhile,higher piezoelectric constant d_(32)-1500–2200 pC/N,d_(15)4000–6000 pC/N and coercive field E_(c)-7:0–9.0 kV/cm have been achieved on(110)cuts.The development trends of relaxor-based ferroelectric crystals are suggested to grow novel crystals with high rhombohedral–tetragonal phase transition temperature T_(rt)>150-160℃ and/or high coercive field Ec and mechanical quality factor Q_(m),to promote growth efficiency of PIMNT crystals and to create new growth methods fitting for the growth of metastable or instable crystals.
文摘Relaxor ferroelectric single crystals PMNT with the size of φ40 mm×80 mm have been grown by a modified Bridgman method and their ferroelectric and piezoelectric properties have been characterized. The properties varied with the compositions and cut types. On the (001) cut, PMNT76/24 single crystals exhibited a dielectric constant ε of about 3 400, a dielectric loss of tanδ 【0.7%, a piezoelectric constant d33 of 980 pC/N, an electromechanical coupling factor kt of 0.55 and Tc of about 110℃. whereas the properties of PMNT67/33 single crystals on (001) cut were betler: e of about 5 300, tan5 【0.6%, d33 up to 3 000 pC/N, kt 0.64, K33 0.93 and Tc of about 150℃. The piezoelectric properties on other cuts such as (110) and (111) were much lower than those on the (001) cut. The rhombohedral PMNT crystals grown by this method showed more excellent piezoelectric properties than those grown by high temperature solution method and higher value of kt than the rhombohedral PZNT single crystals. it has also
基金Project supported by the National Natural Science Foundation of China (No. 59995520), the Chinese Academy of Sciences and Shanghai Municipal Government.
文摘High-performance relaxor ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 have been grown successfully by a modified Bridgman method. They have the size of 25×25×50 mm3 and are of pure perovskite phases with tetragonal or rhombohedral structures. Their {001} faces appear dominantly, which can be interpreted by the model of an-ionic coordination polyhedral growth units. Main macro defects observed under optical microscopes and SEM can be reduced or removed by improving growth parameters after understanding their formation mechanism. 71°or 109°macrodomains in rhombohedral PMNT 76/24 crystals and 90°macrodomains in tetragonal PMNT 65/35 crystals have been observed by optical microscopes. It has been found that the transition from microdomains to macrodomains can be induced by compositions. Both the imaging mechanism of non-180° domains and the relation between domain configurations and ferroelectric phase transition have been analyzed.
文摘The features of the single crystals 0.76PMN-0.24PT in dielectric, ferroelectric, pyroelectric properties and domain structures indicate that they are located between typical ferroelectrics and normal ones. The unpoled crystals present a transitional domain configuration between microdomains and typical macrodomains while the crystals on (001) cuts undergo field-induced phase transition under poling, showing two special temperature points Td and Tm during the succedent heating procedure. The dielectric constant starts to decrease drastically at Td during cooling, or the transformation from induced macrodomain to transitional domain takes place at Td during heating. Ferroelectric-paraelectric phase transition or depolarization continues within the whole temperature range of Td-Tm, where ferroelectric phase in the form of transitional macrodomains coexists with paraelectric phase. Then the crystals macroscopically transoform into paraelectric phase containing ferroelectric microdomains at a temperature
文摘This collection presents 505 papers on ferroelectricity in single crystals,ceramics and polymers in which pointed or elliptical hysteresis loops would testify to their ferroelectric properties.In some papers,the authors ensure that ferroelectricity can occur even in materials that do not have a polar axis of symmetry.
基金supports by the National Natural Science Foundation of China through Grant No.10772090National Basic Research Program of China through Grant No.2004CB619304,are greatly acknowledged.
文摘Single crystals of(1x) Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PMN-xPT)near their morphotropic phase boundaries(MPBs)are under extensive investigations for their extraordinary high dielectric and piezoelectric behavior.Applications of those single crystals facilitated the breakthrough in ultrasonic transducer materials and devices.Ferroelectric materials are known to be fragile which often leads to various reliability failures in applications involving electric loadings.In a mechanical sense,the failure modes concern the fracture under an intensive electric field,and the fatigue crack propagation under an alternating electric field.In an electrical sense,the failure is exhibited by degenerated hysteresis loop by shrinking the remnant polarization and expanding the coercive field.All these modes degrade the performance for ferroelectric devices.As a departure from the tetragonal TÞferroelectric materials,exemplified by BaTiO_(3) and Pb(ZrTi)O_(3),the domain structures of PMN-PT around the MPB are versatile and intricate,depending sensitively on the composition variation,orientation and previous loading history.In this review,the attention is mainly focused on three aspects.First,the phase fragility and multiphase coexistence are presented for both[100]-and[101]-oriented PMN-PT single crystals.Second,investigations on electric field-induced fatigue crack propagation are described,along with the orientation effect on the crack propagation behavior.Third,the inverse effects of the phase transition and fatigue crack growth on the polarization behavior,or the interaction between the mechanical and electrical degradations will be elucidated.The review aims for better understanding the underlying mechanism for the ultrahigh performance of the PMN-PT single crystals,to bridge the studies of ferroelectric materials from the mechanical and electrical senses,as well as to evaluate the reliability of PMN-PT single crystals under device applications.
基金supported by the Natural Science Foundation of China(11274339)
文摘A two-dimensional vector hydrophone was developed utilizing the PMN-PT relaxor ferroelectric single crystal,which is composed of a dual-axis piezoelectric composite flexural beam accelerometer and PZT-5 piezoelectric ceramic rings.Based on the principle of elastic mechanics and underwater particle velocity measurement,the receiving voltage sensitivity of the flexural beam vector hydrophone is derived.The influence of stress distribution in the flexural beam on the performance of hydrophones is analyzed,and the match between PMNPT single crystal cells and the structure of flexural beam is studied.The tested results indicate that the PMN-PT hydrophone presents an 11 dB increase in sensitivity and a 3 dB decrease in self-noise than the PZT-5 one.
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.
基金supported by the National Natural Sciences Foundation of China(Grant No.59995520)the National“863”High Technology Research and Development Program of China(Grant No.2001AA325030)the National“973”Key Basic Program of China(Grant No.2002CB613307)
文摘The piezoresponse behavior dependence of the Pb(Mg1/3Nb2/3)O3-30%PbTiO3 single crystal on the vacuum degree has been investigated by scanning force microscopy in the piezoresponse mode under high vacuum. Unusual piezo- response behavior related to the screening charges compensation mechanism is observed on the (111) crystal face. The significant piezoresponse degradation behavior with low piezoresponse signal under high vacuum is attributed to the instability of the polarization state due to the insufficient compensation of the intrinsic screening charges for the polarization charges in PMN-30%PT single crystal. In contrast, the remarkable domain contrast of the sample at ambient pressure is owing to the dominant surface screening charges deriving from surface adsorption, which plays an important role in determining the stability of the domain behavior and in achieving the optimal properties.
