Multifunctional lead-free double perovskites demonstrate remarkable potential towards applications in various fields.Herein,an environmentally-friendly,low-cost,high-throughput Cs_(2)NaFeCl_(6) single crystal with exc...Multifunctional lead-free double perovskites demonstrate remarkable potential towards applications in various fields.Herein,an environmentally-friendly,low-cost,high-throughput Cs_(2)NaFeCl_(6) single crystal with exceedingly high thermal stability is designed and grown.It obtains a cubic lattice system in the temperature range of 80-500 K,accompanied by a completely reversible chromatic variation ranging from yellow to black.Importantly,the intriguing thermochromism is proved to own extremely high reproducibility(over 1000 cycles)without a hysteretic effect,originating from its structural flexibility that including(i)the noteworthy distortion/deformation of[NaCl_(6)]5−and[FeCl_(6)]3−octahedra;(ii)order-disorder arrangement transition of[NaCl_(6)]5−and[FeCl6]3−octahedra as the function of temperature.This study paves the way towards a new class of smart windows and camouflage coatings with an unprecedented colour range based on a Cs_(2)NaFeCl_(6) perovskite.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
0.14 at%Mn-doped 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3(0.95NBT-0.05BT)lead-free single crystals were grown by a top-seeded solution growth method(TSSG).X-ray powder diffraction measurement showed that the as-grown single cr...0.14 at%Mn-doped 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3(0.95NBT-0.05BT)lead-free single crystals were grown by a top-seeded solution growth method(TSSG).X-ray powder diffraction measurement showed that the as-grown single crystals exhibit rhombohedral perovskite structure with apparent distortion.With the increase of temperature,successive structural phase transitions occur in the Mn-doped 0.95NBT-0.05BT single crystals.After poling,apparent dielectric anomaly is induced accompanied by the increase of the character of diffuse phase transition and the decrease of the value of dielectric constant.The Mn-doped0.95NBT-0.05BT single crystals exhibit complex domain structure,in which micro and macro domains coexist with statistically 4mm symmetry.The Mn-doped 0.95NBT-0.05BT lead-free single crystals exhibit excellent piezoelectric and pyroelectric properties,which will lead to promising advance in piezoelectric and pyroelectric applications.The infrared-absorption band occurred around 630.6 cm 1can be assigned to the"stretching"normal vibration of[Na1/2Bi1/2]/Ti-O group.The three diffused Raman bands centered around 300,560 and 800 cm 1can be attributed to F2g[TiO6]bending vibration,A1g[TiO6]stretching vibration and"soft mode"mixed by bending and stretching vibrations.展开更多
The electrical conductivity of a C60 single crystal around 274 K and the specific heat of C60 crystals from 150 to 340 K have been measured.The delta-like specific heat peak at about 251 K related to the first-order p...The electrical conductivity of a C60 single crystal around 274 K and the specific heat of C60 crystals from 150 to 340 K have been measured.The delta-like specific heat peak at about 251 K related to the first-order phase transition has been reported.The activation energy change around 274 K and the lambda-like specific heat peak beginning at 270 K and ending at 310 K show that there is an orientational phase transition in fcc C60 crystals above 251 K.By taking the symmetry into consideration and further analyzing lambda-like specific heat peak and the activation energy change around 274 K,the conclusion has been reached that this new phase transition is an orientational structure transition from the merohedral twinning fcc to the orientationally disordered fcc.The temperature of free rotation of C60 molecules is about 281 K.展开更多
Temperature and electric field dependences of the dielectric behavior and phase transition for[111]-oriented 0.23PIN–0.52PMN–0.25PT(PIN-PMN–0.25PT)and 0.24PIN–0.43PMN–0.33PT(PIN–PMN–0.33PT)single crystals were ...Temperature and electric field dependences of the dielectric behavior and phase transition for[111]-oriented 0.23PIN–0.52PMN–0.25PT(PIN-PMN–0.25PT)and 0.24PIN–0.43PMN–0.33PT(PIN–PMN–0.33PT)single crystals were investigated over a temperature range from100℃ to 250℃ using field-heating(FH)dielectric measurements.The transition phenomenon from ferroelectric microdomain to macrodomain was found in rhombohedra(R)phase region in the single crystals under dc bias.This transition temperature T_(f) of micro-to-macrodomain is sensitive to dc bias and move quickly to lower temperature with increasing dc bias.The phase transition temperatures in the two single crystals shift toward high temperature and the dielectric permittivities at the phase transition temperature decrease with increasing dc bias.Especially,the phase transition peaks are gradually broad in PIN–PMN–0.33PT single crystal with the increasing dc bias.Effects of dc bias on the dielectric behavior and phase transition in PIN–PMN–PT single crystals are discussed.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
By molecular dynamics simulations employing an embedded atom method potential, we have investigated structural transformations in single crystal A1 caused by uniaxial strain loading along the [001], [011] and [111] di...By molecular dynamics simulations employing an embedded atom method potential, we have investigated structural transformations in single crystal A1 caused by uniaxial strain loading along the [001], [011] and [111] directions. We find that the structural transition is strongly dependent on the crystal orientations. The entire structure phase transition only occurs when loading along the [001] direction, and the increased amplitude of temperature for [001] loading is evidently lower than that for other orientations. The morphology evolutions of the structural transition for [011] and [111] loadings are analysed in detail. The results indicate that only 20% of atoms transit to the hcp phase for [011] and [111] loadings, and the appearance of the hcp phase is due to the partial dislocation moving forward on {lll}fcc family. For [011] loading, the hcp phase grows to form laminar morphology in four planes, which belong to the {111}fcc family; while for [111] loading, the hcp phase grows into a laminar structure in three planes, which belong to the {111}fcc family except for the （111） plane. In addition, the phase transition is evaluated by using the radial distribution functions.展开更多
基金The research was funded by the National Natural Science Foundation of China(No.51802120,51872126,22075103,51672111)Guangdong Basic and Applied Basic Research Foundation for Distinguished Young Scholar(No.2019B151502030)+7 种基金Natural Science Foundation of Guangdong Province(No.2018030310181)the Science and Technology Plan Project of Guangzhou(No.202002030159)Guangdong Basic and Applied Basic Research Foundation for Young Scholar(No.2020A1515111057)‘100 Talents Program of Hebei Province’(No.E2014100008)the Fundamental Research Funds for the Central Universities(No.21619406)X.Y.thanks for the Special Funds for the Cultivation of Guangdong College Students'Scientific and Technological Innovation("Climbing Program"Special Funds)(No.pdjh2019a0055)J.Fan also thanks for the project support for"Young Top talents"in the Pearl River Talent Project of Guangdong Province(2017GC010424)the Guangdong Provincial Innovation and Entrepreneurship Project(grant 2016ZT06D081).
文摘Multifunctional lead-free double perovskites demonstrate remarkable potential towards applications in various fields.Herein,an environmentally-friendly,low-cost,high-throughput Cs_(2)NaFeCl_(6) single crystal with exceedingly high thermal stability is designed and grown.It obtains a cubic lattice system in the temperature range of 80-500 K,accompanied by a completely reversible chromatic variation ranging from yellow to black.Importantly,the intriguing thermochromism is proved to own extremely high reproducibility(over 1000 cycles)without a hysteretic effect,originating from its structural flexibility that including(i)the noteworthy distortion/deformation of[NaCl_(6)]5−and[FeCl_(6)]3−octahedra;(ii)order-disorder arrangement transition of[NaCl_(6)]5−and[FeCl6]3−octahedra as the function of temperature.This study paves the way towards a new class of smart windows and camouflage coatings with an unprecedented colour range based on a Cs_(2)NaFeCl_(6) perovskite.
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
基金supported by the National Natural Science Foundation of China(51242006)the Qing Lan Project,the Key Laboratory of Inorganic Function Material and Device,Chinese Academy of Sciences(KLIFMD-2011-02)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘0.14 at%Mn-doped 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3(0.95NBT-0.05BT)lead-free single crystals were grown by a top-seeded solution growth method(TSSG).X-ray powder diffraction measurement showed that the as-grown single crystals exhibit rhombohedral perovskite structure with apparent distortion.With the increase of temperature,successive structural phase transitions occur in the Mn-doped 0.95NBT-0.05BT single crystals.After poling,apparent dielectric anomaly is induced accompanied by the increase of the character of diffuse phase transition and the decrease of the value of dielectric constant.The Mn-doped0.95NBT-0.05BT single crystals exhibit complex domain structure,in which micro and macro domains coexist with statistically 4mm symmetry.The Mn-doped 0.95NBT-0.05BT lead-free single crystals exhibit excellent piezoelectric and pyroelectric properties,which will lead to promising advance in piezoelectric and pyroelectric applications.The infrared-absorption band occurred around 630.6 cm 1can be assigned to the"stretching"normal vibration of[Na1/2Bi1/2]/Ti-O group.The three diffused Raman bands centered around 300,560 and 800 cm 1can be attributed to F2g[TiO6]bending vibration,A1g[TiO6]stretching vibration and"soft mode"mixed by bending and stretching vibrations.
基金Project supported by the National Natural Science Foundation of China.
文摘The electrical conductivity of a C60 single crystal around 274 K and the specific heat of C60 crystals from 150 to 340 K have been measured.The delta-like specific heat peak at about 251 K related to the first-order phase transition has been reported.The activation energy change around 274 K and the lambda-like specific heat peak beginning at 270 K and ending at 310 K show that there is an orientational phase transition in fcc C60 crystals above 251 K.By taking the symmetry into consideration and further analyzing lambda-like specific heat peak and the activation energy change around 274 K,the conclusion has been reached that this new phase transition is an orientational structure transition from the merohedral twinning fcc to the orientationally disordered fcc.The temperature of free rotation of C60 molecules is about 281 K.
基金supported by the National High Technology Research and Development Program of China(863 Program)(Grant No.2012AA03A704).
文摘Temperature and electric field dependences of the dielectric behavior and phase transition for[111]-oriented 0.23PIN–0.52PMN–0.25PT(PIN-PMN–0.25PT)and 0.24PIN–0.43PMN–0.33PT(PIN–PMN–0.33PT)single crystals were investigated over a temperature range from100℃ to 250℃ using field-heating(FH)dielectric measurements.The transition phenomenon from ferroelectric microdomain to macrodomain was found in rhombohedra(R)phase region in the single crystals under dc bias.This transition temperature T_(f) of micro-to-macrodomain is sensitive to dc bias and move quickly to lower temperature with increasing dc bias.The phase transition temperatures in the two single crystals shift toward high temperature and the dielectric permittivities at the phase transition temperature decrease with increasing dc bias.Especially,the phase transition peaks are gradually broad in PIN–PMN–0.33PT single crystal with the increasing dc bias.Effects of dc bias on the dielectric behavior and phase transition in PIN–PMN–PT single crystals are discussed.
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supported by the Science Foundation for Development of Science and Technology of China Academy of Engineering Physics (Grant Nos. 2008B0101008 and 2009A0101004)
文摘By molecular dynamics simulations employing an embedded atom method potential, we have investigated structural transformations in single crystal A1 caused by uniaxial strain loading along the [001], [011] and [111] directions. We find that the structural transition is strongly dependent on the crystal orientations. The entire structure phase transition only occurs when loading along the [001] direction, and the increased amplitude of temperature for [001] loading is evidently lower than that for other orientations. The morphology evolutions of the structural transition for [011] and [111] loadings are analysed in detail. The results indicate that only 20% of atoms transit to the hcp phase for [011] and [111] loadings, and the appearance of the hcp phase is due to the partial dislocation moving forward on {lll}fcc family. For [011] loading, the hcp phase grows to form laminar morphology in four planes, which belong to the {111}fcc family; while for [111] loading, the hcp phase grows into a laminar structure in three planes, which belong to the {111}fcc family except for the （111） plane. In addition, the phase transition is evaluated by using the radial distribution functions.
