scholarly journals Molecular–Statistical Theory for the Description of Re-Entrant Ferroelectric Phase

Crystals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 583
Author(s):  
Alexander V. Emelyanenko
Keyword(s):  
Phase Transition ◽  
Electric Field ◽  
Dielectric Response ◽  
Temperature Scale ◽  
Statistical Approach ◽  
Ferroelectric Phase ◽  
Dipole Interaction ◽  
Normal Phase ◽  
Smectic Layer ◽  
Antiferroelectric Phase

The re-entrant ferroelectric phase (Sm- C re * ) is investigated in the framework of a molecular–statistical approach. It was found that anticlinic synpolar along the smectic layer normal phase can arise below the antiferroelectric phase (Sm- C A * ) in the temperature scale, and we suggest this phase to be Sm- C re * . We have shown that in the vicinity of Sm- C A * –Sm- C re * phase transition temperature, a very small electric field can cause a transition into the bidomain synclinic phase, where the helical pitch is unwound and the tilt planes have contributions either along or against the electric field. The helical rotation, elasticity and deformation of the Sm- C * , Sm- C A * and Sm- C re * structures without electric field or in the presence of electric field, as well as the dielectric response, are investigated. It is shown that Sm- C re * can arise solely due to the dipole–dipole interaction, and thus, in contrast to the conventional (improper) ferroelectric Sm- C * , appears to be the proper ferroelectric phase.

Influence of Zr/Sn Ratio Electric Properties of PLZST Ceramic

2013 ◽  
Vol 547 ◽  
pp. 101-105 ◽  
Author(s):  
Jin Fei Wang ◽  
Tong Qing Yang ◽  
K. Wei ◽  
G. Li ◽  
Yong Xiang Li
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Dielectric Loss ◽  
Electric Field ◽  
Perovskite Structure ◽  
Ferroelectric Phase ◽  
Hysteresis Loops ◽  
Ferroelectric Ceramics ◽  
Antiferroelectric Phase ◽  
Lower Temperature

(Pb0.97La0.02)(Zr0.92-xSnxTi0.08)O3 (PLZST) ferroelectric ceramics with x=0.40, 0.25, 0.15, respectively, were investigated. It was found that these ceramics with different Zr:Sn ratios were perovskite structure. With increasing of Zr:Sn ratio, the phase-transition electric-field of antiferroelectric to ferroelectric phase increased. when x>0.15,All the samples have double hysteresis loops with antiferroelectric phase characteristics. Yet, when the electric field was removed at lower temperature of -5oC and -20oC, for x=0.25 and 0.40, the electric field induced FE phase can remain metastable FE state. But for x=0.15, the induced FE phase recover to AFE phase even at -20oC. Yet, electric field induced FE phase exist as metastable FE phase. TFE-AFE of the samples was -5oC, -20oC, when x=0.40, x=0.25, respectively. With increasing of Zr:Sn ratio, TFE-AFE increaseddecreased, Tc was hardly changed, but the dielectric constant increased from ~2500 to ~6000, the peak changed sharply, dielectric loss increased continuously with increasing of Zr:Sn ratio.

Use of an External Electric Field to Convert the Paraelectric Phase to the Ferroelectric Phase in Ultra-thin Copolymer Films of P(VDF-TrFE)

2000 ◽  
Vol 655 ◽  
Author(s):  
Matt Poulsen ◽  
S. Adenwalla ◽  
Stephen Ducharme ◽  
V.M. Fridkin ◽  
S.P. Palto ◽  
...  
Keyword(s):  
Phase Transition ◽  
Electric Field ◽  
External Electric Field ◽  
Ferroelectric Phase ◽  
Paraelectric Phase ◽  
Continuous Process ◽  
Structural Phase ◽  
X Ray Diffraction ◽  
Layer Spacing ◽  
X Ray

AbstractX-ray diffraction was used to probe the structural changes associated with the conversion of the paraelectric phase to the ferroelectric phase that results from the application of a large external electric field. The samples under study are ultrathin (150 to 250 Å) Langmuir-Blodgett films of the copolymer vinylidene fluoride (70%) with trifluoroethylene (30%) deposited on aluminum-coated silicon. Theta-2theta X-ray diffraction was used to measure the change in inter-layer spacing perpendicular to the film surface. Upon heating at zero external electric field, the crystalline films undergo a structural phase transition, at 100± 5°C, from the all-trans ferroelectric phase to the trans-gauche paraelectric phase. [1,2] Above the phase transition temperature, the non-polar paraelectric phase can be converted back to the polar ferroelectric phase, in a smooth continuous process, using a large external electric field (∼1 GV/m). For example, at 100° C the ferroelectric phase first appears above 0.2 GV/m and increases steadily in proportion while the paraelectric phase decreases until complete conversion to the ferroelectric phase is achieved at approximately 0.6 GV/m.

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