In this study,a new Dy-Eu-Tm co-doped cubic phase stabilized bismuth oxide solid electrolyte system was synthesized by using solid-state reaction method in atmospheric conditions.Before conductivity measurements,X-ray...In this study,a new Dy-Eu-Tm co-doped cubic phase stabilized bismuth oxide solid electrolyte system was synthesized by using solid-state reaction method in atmospheric conditions.Before conductivity measurements,X-ray diffraction(XRD)pro files of the annealed samples show that created mixtures have heterogeneous phase,but after conductivity measurements,the face-centered cubic(FCC)crystal structure is stabilized for all samples.Also,the increase in total dopant rate causes an increase in full width half maxima(FWHM)of main peak(111)on the XRD pattern while average crystal size decreases with it.On the other hand,the highest conductivity value was obtained for the sample having 15%total dopant rate with 0.62 S/cm at 750℃,whose dopants are evenly distributed in mole percent.Differential thermal analysis(DTA)results of the samples having 1:1:1 and 1:2:1 dopant content ratios show that endothermic peak occurs on their DTA curve,indicating crystal structure transformation such as phase transition or order-disorder transition.Also,thermo-gravimetric analysis(TGA)depending on temperature was evaluated in terms of mass loss.According to TGA curves,mass loss for both heating and cooling process can be negligible due to the small fluctuations(2%)on their TGA curves.展开更多
The kinetics of internal boundaries relaxation: antiphase domain boundaries and interphase boundaries-in the conditions of high-temperature annealing and the structure transformations are investigated in homophase an...The kinetics of internal boundaries relaxation: antiphase domain boundaries and interphase boundaries-in the conditions of high-temperature annealing and the structure transformations are investigated in homophase and heterophase systems. Homophase systems look like ordered binary alloy and include antiphase domain boundaries of various orientation. Clear components border on ordered alloy in heterophase systems and two processes take place simultaneously here-disordering of binary alloy and solution in ordered phase of clear component. Computer experiment is realized in the sphere of temperatures close to the temperature of order-disorder phase transition in the limits of two-dimensional model of atom diffusion at the vacant knots of crystal lattics.展开更多
The structural phase transition compound {[（CH3）2CHCH2]2NH2}·[CF3COO] （1） has been synthesized based on the diisobutylamine and trifluoroacetic acid. The DSC data reveal that 1 undergoes a phase transition at...The structural phase transition compound {[（CH3）2CHCH2]2NH2}·[CF3COO] （1） has been synthesized based on the diisobutylamine and trifluoroacetic acid. The DSC data reveal that 1 undergoes a phase transition at 277 K （Tc）. When one chlorine atom replaces one fluorine atom on trifluoroacetate anion, three order-disorder phase transitions at 251 K （Ti）, 282 K （T2） and 290 K could be achieved owing to a stepwise release of rotation motions of the anion and cation in {[（CH3）2CHCH2]2NH2}·[CF2C[COO] （2）. Based on the variable temperature crystal structures, the phase transition in compound 1 is triggered by the rotation of three fluorine atoms on the trifluoroacetate anion synchronized with the motions of the methyl groups on the diisobutylammonium cation. However, in compound 2, the phase transitions can be realized by a sequence of motions of both the anion and cation. Besides, the dielectric- temperature dependences were investigated in order to prove this regulation process. All of this investigation will be beneficial to design and synthesis of the novel phase transition materials and molecular dielectric materials on pur- pose.展开更多
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
Based on cluster variation method (CVM) and natural iteration method (MM),order-disorder phase transition in the intercalation compounds M_(1/2)TiS_2 is simulated bycomputer. The favorable conditions, under which 3^(1...Based on cluster variation method (CVM) and natural iteration method (MM),order-disorder phase transition in the intercalation compounds M_(1/2)TiS_2 is simulated bycomputer. The favorable conditions, under which 3^(1/2)a_0 x a_0 superstructure is formed, aregiven, and the results are in good agreement with the experiments and theoretical calculations. Therelationship between critical temperature and M-ion-vacancy interaction parameter is linear.展开更多
Order–disorder phase transitions for CH3NH3PbCl3 are studied with density functional theory. Our calculations show that the disorder is manifested in two aspects in the cubic phase, namely, the disorder of orientatio...Order–disorder phase transitions for CH3NH3PbCl3 are studied with density functional theory. Our calculations show that the disorder is manifested in two aspects in the cubic phase, namely, the disorder of orientation and rotation of organic groups. Organic groups of [CH3] and [NH3] in cubic crystals can easily rotate around its C3 axis. At the same time,[CH3NH3]^+ organic groups can also orient to different spatial directions due to the weak interactions between organic group and inorganic frame. Our results show that its possible phase transition path starts from the deviation of organic groups from the crystal c-axis. Its structural transition changes from disordered cubic phase to hydrogen-only disordered tetragonal structure in the process of decreasing symmetry. The disordered high temperature cubic phase can be expressed as a statistical average of substructures we rebuilt. The electrostatic repulsive force between adjacent organic groups triggers out the formation of low temperature phase on cooling.展开更多
To switch quadratic nonlinear optical（NLO） effects has become an exciting branch of the NLO material science. However, solid-state molecular crystals showing tunable and switchable NLO behaviors remain scarce. Here,...To switch quadratic nonlinear optical（NLO） effects has become an exciting branch of the NLO material science. However, solid-state molecular crystals showing tunable and switchable NLO behaviors remain scarce. Here, we report an organic picrate-based binary molecular crystal, triethylammonium picrate（TEAP）, which undergoes an above-room-temperature phase transition at T_c=319 K, being solidly confirmed by the thermal and dielectric measurements. A large thermal hysteresis of ~7 K discloses the first-order feature for its phase transition. More strikingly, the quadratic NLO effects of TEAP can be switched in the vicinity of Tc. That is, TEAP exhibits NLO-active response of ~1.5 times as large as that of KDP below T_c（i.e., NLO-on state）, while its NLO effects totally disappear above T_c（NLO-off state）. Structure analyses disclose that the order-disorder transformations of triethylammonium cations and picrate anions collectively contribute to its phase transition, as well as switchable NLO behaviors. This work opens up a new pathway to the designing and assembling of stimuli-responsive materials.展开更多
文摘In this study,a new Dy-Eu-Tm co-doped cubic phase stabilized bismuth oxide solid electrolyte system was synthesized by using solid-state reaction method in atmospheric conditions.Before conductivity measurements,X-ray diffraction(XRD)pro files of the annealed samples show that created mixtures have heterogeneous phase,but after conductivity measurements,the face-centered cubic(FCC)crystal structure is stabilized for all samples.Also,the increase in total dopant rate causes an increase in full width half maxima(FWHM)of main peak(111)on the XRD pattern while average crystal size decreases with it.On the other hand,the highest conductivity value was obtained for the sample having 15%total dopant rate with 0.62 S/cm at 750℃,whose dopants are evenly distributed in mole percent.Differential thermal analysis(DTA)results of the samples having 1:1:1 and 1:2:1 dopant content ratios show that endothermic peak occurs on their DTA curve,indicating crystal structure transformation such as phase transition or order-disorder transition.Also,thermo-gravimetric analysis(TGA)depending on temperature was evaluated in terms of mass loss.According to TGA curves,mass loss for both heating and cooling process can be negligible due to the small fluctuations(2%)on their TGA curves.
文摘The kinetics of internal boundaries relaxation: antiphase domain boundaries and interphase boundaries-in the conditions of high-temperature annealing and the structure transformations are investigated in homophase and heterophase systems. Homophase systems look like ordered binary alloy and include antiphase domain boundaries of various orientation. Clear components border on ordered alloy in heterophase systems and two processes take place simultaneously here-disordering of binary alloy and solution in ordered phase of clear component. Computer experiment is realized in the sphere of temperatures close to the temperature of order-disorder phase transition in the limits of two-dimensional model of atom diffusion at the vacant knots of crystal lattics.
基金This work was financially supported by the 973 Pro- ject from the Ministry of Science and Technology of China （No. 2014CB84561）, and the National Natural Science Foundation of China （Nos. 21571150, 21431005 and 21390391）.
文摘The structural phase transition compound {[（CH3）2CHCH2]2NH2}·[CF3COO] （1） has been synthesized based on the diisobutylamine and trifluoroacetic acid. The DSC data reveal that 1 undergoes a phase transition at 277 K （Tc）. When one chlorine atom replaces one fluorine atom on trifluoroacetate anion, three order-disorder phase transitions at 251 K （Ti）, 282 K （T2） and 290 K could be achieved owing to a stepwise release of rotation motions of the anion and cation in {[（CH3）2CHCH2]2NH2}·[CF2C[COO] （2）. Based on the variable temperature crystal structures, the phase transition in compound 1 is triggered by the rotation of three fluorine atoms on the trifluoroacetate anion synchronized with the motions of the methyl groups on the diisobutylammonium cation. However, in compound 2, the phase transitions can be realized by a sequence of motions of both the anion and cation. Besides, the dielectric- temperature dependences were investigated in order to prove this regulation process. All of this investigation will be beneficial to design and synthesis of the novel phase transition materials and molecular dielectric materials on pur- pose.
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.
基金This work was supported by the Foundation of Civil Aviation University of China (No. 2001-3-18).
文摘Based on cluster variation method (CVM) and natural iteration method (MM),order-disorder phase transition in the intercalation compounds M_(1/2)TiS_2 is simulated bycomputer. The favorable conditions, under which 3^(1/2)a_0 x a_0 superstructure is formed, aregiven, and the results are in good agreement with the experiments and theoretical calculations. Therelationship between critical temperature and M-ion-vacancy interaction parameter is linear.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51572219,51872227,11204239,and 11447030)the Project of Natural Science Foundation of Shaanxi Province of China(Grant Nos.2015JM1018,2013JQ1018,15JK1759,and 15JK1714)the Science Foundation of Northwest University of China(Grant No.12NW06)
文摘Order–disorder phase transitions for CH3NH3PbCl3 are studied with density functional theory. Our calculations show that the disorder is manifested in two aspects in the cubic phase, namely, the disorder of orientation and rotation of organic groups. Organic groups of [CH3] and [NH3] in cubic crystals can easily rotate around its C3 axis. At the same time,[CH3NH3]^+ organic groups can also orient to different spatial directions due to the weak interactions between organic group and inorganic frame. Our results show that its possible phase transition path starts from the deviation of organic groups from the crystal c-axis. Its structural transition changes from disordered cubic phase to hydrogen-only disordered tetragonal structure in the process of decreasing symmetry. The disordered high temperature cubic phase can be expressed as a statistical average of substructures we rebuilt. The electrostatic repulsive force between adjacent organic groups triggers out the formation of low temperature phase on cooling.
基金supported by the National Natural Science Foundation of China(Nos. 21622108, 21525104, 21601188, 91422301, 21373220, 51402296 and 51502290)the Natural Science Foundation of Fujian Province(No. 2015J05040)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(No. XDB20000000)the Youth Innovation Promotion of CAS(No. 2014262)the State Key Laboratory of Luminescence and Applications(No. SKLA-2016-09)
文摘To switch quadratic nonlinear optical（NLO） effects has become an exciting branch of the NLO material science. However, solid-state molecular crystals showing tunable and switchable NLO behaviors remain scarce. Here, we report an organic picrate-based binary molecular crystal, triethylammonium picrate（TEAP）, which undergoes an above-room-temperature phase transition at T_c=319 K, being solidly confirmed by the thermal and dielectric measurements. A large thermal hysteresis of ~7 K discloses the first-order feature for its phase transition. More strikingly, the quadratic NLO effects of TEAP can be switched in the vicinity of Tc. That is, TEAP exhibits NLO-active response of ~1.5 times as large as that of KDP below T_c（i.e., NLO-on state）, while its NLO effects totally disappear above T_c（NLO-off state）. Structure analyses disclose that the order-disorder transformations of triethylammonium cations and picrate anions collectively contribute to its phase transition, as well as switchable NLO behaviors. This work opens up a new pathway to the designing and assembling of stimuli-responsive materials.
