scholarly journals Размерный эффект в нанокомпозитах на основе молекулярного сегнетоэлектрика бромида диизопропиламмония

2019 ◽  
Vol 61 (2) ◽  
pp. 273
Author(s):  
C.B. Барышников ◽  
А.Ю. Милинский ◽  
E.B. Чарная ◽  
И.В. Егорова
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Transition Temperature ◽  
Dielectric Properties ◽  
Size Effects ◽  
Low Temperatures ◽  
Structural Phase ◽  
Theoretical Models ◽  
Temperature Hysteresis ◽  
And Diffusion

AbstractWe present the results of studies of the dielectric properties of nanocomposites based on Al_2O_3 oxide films with a pore size of 330 and 60 nm with particles of an organic ferroelectric diisopropylammonium bromide (C_6H_16BrN, DIPAB) introduced into the pores, aimed at determining the size dependences of phase transition parameters. A shift in the phase transition to low temperatures and diffusion of the transition are found, which become more significant for smaller pores. A broadening of the temperature hysteresis of the dielectric constant of nanocomposites during the phase transition was also observed. The decrease in the phase transition temperature in nanocomposites with DIPAB nanoparticles is consistent with theoretical models of the size effects on the structural phase transition.

scholarly journals Dielectric and thermal properties of organic ferroelectric (R)-3-quinuclidinol in porous glass

2021 ◽  
Vol 2103 (1) ◽  
pp. 012198
Author(s):  
A Yu Milinskiy ◽  
S V Baryshnikov ◽  
E V Charnaya ◽  
N I Uskova
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Thermal Properties ◽  
Size Effects ◽  
Low Temperatures ◽  
Average Pore Size ◽  
Structural Phase ◽  
Theoretical Models ◽  
Average Pore ◽  
Porous Glasses

Abstract The results of studies of the dielectric constant ε′ and the DTA signal of a new organic ferroelectric (R)-3-quinuclidinol (C7H13NO), embedded in porous glasses with an average pore size of 100 nm, are presented. The phase transition was found to shift to low temperatures by 3 K upon heating and 6 K upon cooling, in comparison with bulk (R)-3-quinuclidinol. A decrease in the phase transition temperature in composites with (R)-3-quinuclidinol nanoparticles is consistent with theoretical models of the influence of size effects on the structural phase transition.

The Microstructure and Dielectric Properties of SrTiO3 Modified 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 Ceramics

2011 ◽  
Vol 687 ◽  
pp. 433-438
Author(s):  
Jing Song Liu ◽  
Tao Li ◽  
Hui Qin Li ◽  
You Chao Xu ◽  
Ji Qiang Yu
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Transition Temperature ◽  
Dielectric Properties ◽  
Spontaneous Polarization ◽  
Relaxor Behavior ◽  
Maximum Dielectric Constant ◽  
Lower Temperature ◽  
Region Size ◽  
Maximum Permittivity

The microstructure and dielectric properties of ferroelectric solutions which is formulated with (1-x)[0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3]-x mol% SrTiO3(x=0, 1, 3 and 5) have been investigated. The ceramics was fabricated by a modified columbite route sintered at 1200 °C. The effects of dopants on microstructure, maximum dielectric constant (εm) and diffuseness of the phase transition, etc. have been studied. It is found that the maximum permittivity (εm) increases to 24968 for the ST-doped (1 mol %) sample, subsequently decreases with ST addition and its corresponding phase-transition-temperature (Tm) shifts to the lower temperature. The variation of εmis caused by the decrease of polar nano-region size, increase of the fluctuation of the component and the increase of the effective spontaneous polarization. The enhancement of relaxor behavior in the PMN-PT sample is explained by the decrease of FE/AFE coupling.

scholarly journals Study of Ferroelectric Phase Transition in Triglycine Selenate Crystal

2021 ◽  
Vol 16 (2) ◽  
Author(s):  
Prabhat Chandra Khanduri ◽  
Trilok Chandra Upadhyay
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Transition Temperature ◽  
Soft Mode ◽  
Structural Phase ◽  
Mode Frequency ◽  
Thermal Dependence ◽  
Triglycine Selenate ◽  
Dielectric Constant And Loss ◽  
Physical Quantities

Triglycine selenate (TGSe) is a Hydrogen bondend order disorder type ferroelectric, which go through a structural phase transition at Tc=295K. TGSe is very similar to the Triglycine Sulphate crystal, which is extensively used in infrared detection. In the present paper we are using double time thermal Green’s function method and modified pseudospin model to discuss ferroelectric behavior of TGSe crystal. Expressions for shift, width, soft mode frequency, dielectric constant, loss and transition temperature have been evaluated. By fitting model values of physical quantities in the theoretical expressions thermal dependence of soft mode frequency, dielectric constant and loss have been calculated in the vicinity of transition temperature. Theoretical results are in well agreement with experimental results of other researchers.

scholarly journals Спектры пропускания монокристаллов гибридных перовскитов MAPbI-=SUB=-3-=/SUB=- вблизи края фундаментального поглощения

2022 ◽  
Vol 130 (1) ◽  
pp. 116
Author(s):  
В.Е. Аникеева ◽  
К.Н. Болдырев ◽  
О.И. Семенова ◽  
М.Н. Попова
Keyword(s):  
Phase Transition ◽  
Absorption Edge ◽  
Structural Phase ◽  
Fundamental Absorption Edge ◽  
Orthorhombic Phase ◽  
Temperature Hysteresis ◽  
First Order ◽  
Hybrid Perovskite ◽  
First Order Phase Transition ◽  
First Order Phase

The paper presents the transmission spectra of hybrid perovskite MAPbI3 single crystals near the fundamental absorption edge in a wide temperature range. The absorption coefficient α of the single crystal samples is estimated at a temperature T = 150 K for the light with a photon energy E = 1.6 eV and at T = 40 K for E = 1.8 eV. The obtained values turned out to be several orders of magnitude smaller than the values of α for thin-film samples known from the literature. A sharp shift of the fundamental absorption edge by ~ 100 meV was observed at a temperature T1 = 160 K of the structural phase transition from the tetragonal to the orthorhombic phase. The temperature hysteresis of the shift of the fundamental absorption edge near T1 was recorded, which is characteristic of a first-order phase transition.

Change of Phase Transition Temperature in Band Engineered Ferroelectric Lanthanum-Modified Bismuth Titanates

2020 ◽  
Vol 20 (11) ◽  
pp. 7135-7139
Author(s):  
Rui Tang ◽  
Sangmo Kim ◽  
Chung Wung Bark
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Ferroelectric Properties ◽  
Solar Spectrum ◽  
Ferroelectric Material ◽  
Transition Temperatures ◽  
Phase Transition Temperatures ◽  
Increasing Temperature

The ferroelectric material chosen for a solar cell has to absorb as much of the solar spectrum as possible, therefore a low band gap is desirable, but it is rarely known for phase transition temperature on the bandgap engineered ferroelectric materials. The phase transition temperature of a ferroelectric material can be determined by monitoring its dielectric constant with increasing temperature, as the dielectric constant changes abruptly at the phase transition temperature. Here, we inform the measurement of the phase transition temperature of the ferroelectric complex oxide Bi3.25La0.75Ti3O12 as well as cobalt and iron doped Bi3.25La0.75Ti3O12 bulk ceramics for photovoltaic cells based on dielectric monitoring with changing temperature. We synthesized lanthanum-modified bismuth-titanate-based ceramics with various doping concentrations transition metal to Ti. X-ray diffraction analysis revealed that all the compounds crystallized in an orthorhombic structure. Their morphologies and size distributions were observed using scanning electron microscopy. From the ultraviolet-visible spectroscopy absorption spectra of the synthesized powder, bandgaps were checked. An inductance-capacitance-resistance meter was used to obtain the relationship between dielectric responses and the temperature of the targets in a tube furnace. We observed that the dielectric constant increases gradually with increasing temperature, until the transition temperature and subsequently decreases, and we were able to determine the phase transition temperatures of the tested materials. Furthermore, the results revealed that all the doped bismuth titanates keep their phase transition temperatures, which were sufficiently high, to maintain their ferroelectric properties above room temperature.

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