Para-Ferroelectric Phase Transition Induces Excellent Second Harmonic Generation Response and Prominent Switchable Dielectric Constant Change based on a Metal-Free Ionic Crystal

CrystEngComm ◽  
2021 ◽  
Author(s):  
Ding-Chong Han ◽  
Yu-Kong Li ◽  
Yao Liu ◽  
Yu-Hui Tan ◽  
Yun Zhi Tang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Ionic Crystal ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Second Harmonic ◽  
Metal Free ◽  
Reversible Phase Transition ◽  
Constant Change ◽  
Reversible Phase

In this paper, a novel metal-free compound: [H2(bpyp)][ClO4]2 (1), (bpyp = 1,3-bis(4-pyridyl) propane), has been successfully synthesized, its undergoing a reversible phase transition around Tc = 256.19 K (Tc is...

Micro Mechanism of BaTiO3 Ferroelectric Phase Transition Described by Electron Cloud Model

2012 ◽  
Vol 479-481 ◽  
pp. 619-622
Author(s):  
Chao Fang ◽  
Liang Yan Chen
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Equilibrium Position ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Cloud Model ◽  
Electron Cloud ◽  
Oxygen Ions ◽  
Expansion Effect ◽  
Coulomb Attraction

In this paper the micro mechanism of BaTiO3 ferroelectric phase transition is studied based on the thermodynamic model using electron cloud model, and further the Curie - Weiss law is explained. The results indicate that the contraction of the electron cloud, as the temperature decreased through Curie temperature, causes oxygen ions shift the equilibrium position, and the Coulomb attraction makes Ti ion shift the equilibrium position causing phase transition; With temperature rising, the ion displacement polarization decreases owing to the electron cloud expansion effect, and the variation of dielectric constant with temperature follows the Curie - Weiss law.

Dielectric characteristics and diffuse ferroelectric phase transition in Sr4La2Ti4Nb6O30 tungsten bronze ceramics

2006 ◽  
Vol 21 (7) ◽  
pp. 1787-1792 ◽  
Author(s):  
X.L. Zhu ◽  
X.M. Chen ◽  
X.Q. Liu ◽  
Y. Yuan
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Tungsten Bronze ◽  
Frequency Dispersion ◽  
Dielectric Characteristics ◽  
Low Dielectric ◽  
Dielectric Data ◽  
Maximum Dielectric Constant

In this work, Sr4La2Ti4Nb6O30 ceramics with tetragonal filled tungsten bronze structure were prepared, and the dielectric characteristics and ferroelectric transition were investigated. The room-temperature dielectric constant of the present ceramics showed very weak frequency dependency; it decreased from 570.4 to 561.7 when the frequency varied from 200 Hz to 1 MHz, and a comparatively low-dielectric loss was observed (in the order of 10−3). Unlike the situation for Ba4Ln2Ti4Nb6O30 (Ln = La, Nd and Sm), Sr4La2Ti4Nb6O30 ceramics showed a diffuse ferroelectric phase transition, and the diffuseness exponent γ was 1.61. Moreover, the obvious frequency dispersion was observed over a broad frequency range from 200 Hz to 1 MHz, and the maximum dielectric constant temperature Tmax shifted to higher temperatures with increasing frequency. The dielectric data agreed closely with the Vogel–Fulcher relationship. We concluded that tungsten bronze Sr4La2Ti4Nb6O30 has the relaxor ferroelectric nature.

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