scholarly journals Tunability modeling and experiments for BaTiO3-based solid solutions

2007 ◽  
Vol 1 (1-2) ◽  
pp. 23-27 ◽  
Author(s):  
Lavinia-Petronela Curecheriu
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Room Temperature ◽  
Ferroelectric State ◽  
Electric Field Dependence ◽  
Para Phase ◽  
Dipolar Moment ◽  
Modeling And Experiments ◽  
Paraelectric State ◽  
Double Well Potential

In this paper, the electric field dependence of the dielectric constant in some BaTiO3-based ferroelectrics is theoretically described by means of the Landau-Ginzburg-Devonshire (LGD) theory and its? approximations valid for low polarizations (Johnson?s equation and even-power relation) when the sample is in its ferroelectric state and by a model considering random non-interacting dipolar units in a double well potential for the paraelectric state. High-voltage tunability data were obtained at room temperature for BaZr0.10Ti0.90O3 and Ba0.70Sr0.30TiO3 ceramics. The data were well fitted by using the Johnson?s approximation for the ferroelectric-relaxor BaZr0.10Ti0.90 O3 and satisfactory for the Ba0.70Sr0.30TiO3 ceramics, close to its ferro-para phase transition. For the last one, the non-interacting dipolar units model allows to determine the average dipolar moment.

scholarly journals Synthesis and characterization of lead-free ternary component BST–BCT–BZT ceramic capacitors

2014 ◽  
Vol 04 (02) ◽  
pp. 1450014 ◽  
Author(s):  
Venkata Sreenivas Puli ◽  
Dhiren K. Pradhan ◽  
Brian C. Riggs ◽  
Shiva Adireddy ◽  
Ram S. Katiyar ◽  
...  
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Energy Density ◽  
Electric Field ◽  
Hysteresis Loop ◽  
Electric Fields ◽  
Room Temperature ◽  
Thermal Hysteresis ◽  
Lead Free ◽  
Maximum Electric Field

Polycrystalline sample of lead-free 1/3( Ba 0.70 Sr 0.30 TiO 3) + 1/3( Ba 0.70 Ca 0.30 TiO 3) + 1/3( BaZr 0.20 Ti 0.80 O 3)( BST - BCT - BZT ) ceramic was synthesized by solid state reaction method. Phase purity and crystal structure of as-synthesized materials was confirmed by X-ray diffraction (XRD). Temperature-dependent dielectric permittivity studies demonstrated frequency-independent behavior, indicating that the studied sample has typical diffuse phase transition behavior with partial thermal hysteresis. A ferroelectric phase transition between cubic and tetragonal phase was noticed near room temperature (~ 330 K). Bulk P–E hysteresis loop showed a saturation polarization of 20.4 μC/cm2 and a coercive field of ~ 12.78 kV/cm at a maximum electric field of ~ 115 kV/cm. High dielectric constant (ε ~ 5773), low dielectric loss (tan δ ~ 0.03) were recorded at room temperature. Discharge energy density of 0.44 J/cm3 and charge energy density of 1.40 J/cm3 were calculated from nonlinear ferroelectric hysteresis loop at maximum electric field. Dielectric constant at variable temperatures and electric fields, ferroelectric to paraelectric phase transition and energy storage properties were thoroughly discussed.

Coupling of Defect Fields to Domains and Phase Transition Characteristics of Ferroelectric Thin Films with Charged Defects

2011 ◽  
Vol 1292 ◽  
Author(s):  
Ibrahim B. Misirlioglu ◽  
Hale N. Cologlu ◽  
Mehmet Yildiz
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Ultrathin Films ◽  
Ferroelectric Thin Films ◽  
Dead Layer ◽  
Ferroelectric State ◽  
Paraelectric State ◽  
Charged Defects ◽  
Extrinsic Effects ◽  
Linear Thermodynamic

ABSTRACTWe analyze the effect of charged defects on the electrical domains, phase transition characteristics and electrical properties of ferroelectric thin films with thin dead layers using a non-linear thermodynamic model. Depending on their density and field strength, defects can pin and couple to electrical domains in the film. For ultrathin films, depolarizing effects dominate and the transition from the paraelectric state is into the multidomain ferroelectric state during cooling and is strongly smeared. The competition between defect induced extrinsic effects and the dead layer related limit is demonstrated.

Dielectric Properties of Pulsed Excimer Laser Ablated BaBi2Nb2O9 Thin Films

2002 ◽  
Vol 748 ◽  
Author(s):  
Apurba Laha ◽  
S. B. Krupanidhi ◽  
S. Saha
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Dielectric Constant ◽  
Temperature Dependence ◽  
Loss Tangent ◽  
Dielectric Response ◽  
Room Temperature ◽  
Dielectric Constant And Loss ◽  
Wide Range ◽  
Room Temperature Dielectric Constant

ABSTRACTThe dielectric response of BaBi2Nb2O9 (BBN) thin films has been studied as a function of frequency over a wide range of temperatures. Both dielectric constant and loss tangent of BBN thin films showed a ‘power law’ dependence with frequency, which was analyzed using the Jonscher's universal dielectric response model. Theoretical fits were utilized to compare the experimental results and also to estimate the value of temperature dependence parameters such as n(T) and a(T) used in the Jonscher's model. The room temperature dielectric constant (ε') of the BBN thin films was 214 with a loss tangent (tanδ) of 0.04 at a frequency of 100 kHz. The films exhibited the second order dielectric phase transition from ferroelectric to paraelectric state at a temperature of 220 °C. The nature of phase transition was confirmed from the temperature dependence of dielectric constant and sponteneous polarization,respectively. The calculated Currie constant for BBN thin films was 4 × 105°C.

High-Performance Lead-Free Barium Titanate Piezoelectric Ceramics

2008 ◽  
Vol 54 ◽  
pp. 7-12 ◽  
Author(s):  
Tomoaki Karaki ◽  
Masatoshi Adachi ◽  
Kang Yan
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Transition Temperature ◽  
Barium Titanate ◽  
Phase Transition Temperature ◽  
Room Temperature ◽  
Electromechanical Coupling ◽  
Electromechanical Coupling Factor ◽  
Coupling Factor ◽  
Piezoelectric Constants

Barium titanate (BaTiO3) ceramics with a high-density were fabricated by two-step sintering method from hydrothermally synthesized 100 nm BaTiO3 nano-particles. The best specimen with an average grain size of 1.6 μm and a density of 5.91 g/cm3 (98.3% of the theoretical value). The dielectric constant was 4500 and electromechanical coupling factor kp was 45%. Large piezoelectric constants d33 = 460 pC/N and d31 = -185 pC/N were observed in the specimens. This was an important practical result towards obtaining a high d33 in non-lead-based BaTiO3 ceramics manufactured by a low-cost process. These results also indicated the possibility of using BaTiO3 ceramics in piezoelectric devices at room temperature. Temperature dependence of dielectric constant showed two peaks located at 24 and 126 oC, corresponding to orthorhombic-to-tetragonal phase transition temperature Tot and Curie temperature Tc, respectively. Owing to the size effect of nanocrystals, Tot shifted to 24 oC. The maximum of electromechanical coupling factor kp appeared close to the phase transition temperature. It also caused a very large temperature coefficient of resonance frequency from room temperature to 60 oC. Hysteresis curve measurement showed a very low coercive field Ec = 115 V/mm. A large Poisson’s ratio, about 0.38, was determined from the ratio of overtone frequency and resonant frequency in the planar mode. The high Poisson’s ratio and the large dielectric constants are most likely the origin of the high piezoelectric constants in the ceramics.

Phase Transition and Crystal Dynamics of 4-Bromobenzyl Alcohol

1998 ◽  
Vol 53 (6-7) ◽  
pp. 436-441 ◽  
Author(s):  
Masao Hashimoto ◽  
Yuko Monobe ◽  
Hiromitsu Terao ◽  
Haruo Niki ◽  
Koichi Mano
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Phase I ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
Room Temperature ◽  
Molecular Motion ◽  
Dielectric Dispersion ◽  
Compound A ◽  
Crystal Dynamics

Abstract For the title compound a phase transition from Phase II to Phase I (low and room temperature phases, respectively) was found at ca. 217 K. The temperature dependence of the 81Br NQR frequency and that of the dielectric constant showed anomalies at ca. 195 K that were tentatively attributed to a higher order phase transition. A similar anomaly was found at ca. 218 K for 4-chlorobenzyl alcohol which showed a II-I transition at 236 K. The dielectric dispersion observed for both compounds at low temperatures indicates an excitation of a molecular motion with the dielectric relaxation rate of ca. 1 kHz. The temperature dependence of the 81Br NQR frequencies of 2-and 3-bromobenzyl alcohol, measured at T > 77 K, gave no evidence of phase transition in their crystals.

Dielectric phase transition of an A2BX4-type perovskite with a pentahedral to octahedral transformation

2020 ◽  
Vol 49 (7) ◽  
pp. 2218-2224 ◽  
Author(s):  
Siqian Chai ◽  
Jianbo Xiong ◽  
Yongshen Zheng ◽  
Rongchao Shi ◽  
Jialiang Xu
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Room Temperature ◽  
High Dielectric Constant ◽  
Low Dielectric Constant ◽  
Dielectric Phase ◽  
Low Dielectric ◽  
High Dielectric

The as-synthesized 2D perovskite [C5H12N]2PbCl4 undergoes an above-room-temperature dielectric phase transition with a reversible pentahedral to octahedron transformation and a high dielectric constant being over twice of the low dielectric constant.

Above room-temperature dielectric switching and semiconducting properties of a layered organic–inorganic hybrid compound: (C6H12N)2Pb(NO3)4

2020 ◽  
Vol 49 (46) ◽  
pp. 16860-16865
Author(s):  
Jia-Ying Jiang ◽  
Qi Xu ◽  
Jia-Jun Ma ◽  
Zhi-Xin Gong ◽  
Chao Shi ◽  
...  
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Structural Phase Transition ◽  
Room Temperature ◽  
Structural Phase ◽  
Hybrid Compound ◽  
Inorganic Hybrid ◽  
Semiconducting Properties

(C6H12N)2Pb(NO3)4, a layered hybrid semiconductor with switchable dielectric constant, undergoes a structural phase transition around 352 K.

Antiferroelectric to Paraelectric Phase Transition in Lead Zirconate Thin Films

1998 ◽  
Vol 541 ◽  
Author(s):  
D.M. Fanning ◽  
I.K. Robinson ◽  
T. Tani ◽  
D. A. Payne
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Room Temperature ◽  
Sol Gel ◽  
Lead Zirconate ◽  
First Order Phase Transition ◽  
Columnar Grains ◽  
Superstructure Peak ◽  
Paraelectric State ◽  
First Order Phase

AbstractLead zirconate, PbZrO3, is antiferroelectric at room temperature and has a first-order phase transition to the paraelectric state at 230°C in bulk crystals. At room temperature, the antiferroelectric Pb displacements along [110] directions produce a superstructure at the (h+¼ k+¼, 1) positions (referenced to pseudo-tetragonal unit cell). The Pb displacements occur perpendicular to the shorter c axis. In this study, the behavior of thin films was compared to the bulk. Films of lead zirconate were deposited onto electroded silicon wafers via the sol gel method. By varying the deposition conditions of the Pt substrate, films with both {111} and {100} preferred orientation were grown. The crystalline film consisted of columnar grains which were not completely aligned with each other, but had a random orientation with respect to the film's perpendicular axis. Measurements of superstructure peak intensities vs. temperature show that the thin films exhibit a much more gradual phase transition to the paraelectric state compared to the bulk. Furthermore, comparison of a and c vs. temperature show this effect, as well as a strain of about 0.5% in c. In the {100} oriented films, we found that the c-axis was oriented perpendicular to the film's surface, meaning they should be classified as (001).

Electron Microscope study of commensurate-incommensurate phase transition in BaZnGeO4

1990 ◽  
Vol 48 (4) ◽  
pp. 172-173
Author(s):  
Naoki Yamamoto ◽  
Makoto Kikuchi ◽  
Tooru Atake ◽  
Akihiro Hamano ◽  
Yasutoshi Saito
Keyword(s):  
Phase Transition ◽  
Electron Microscope Study ◽  
Room Temperature ◽  
Hexagonal Lattice ◽  
Ferroelectric Materials ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Periodic Arrays ◽  
Modulation Wave Vector

BaZnGeO4 undergoes many phase transitions from I to V phase. The highest temperature phase I has a BaAl2O4 type structure with a hexagonal lattice. Recent X-ray diffraction study showed that the incommensurate (IC) lattice modulation appears along the c axis in the III and IV phases with a period of about 4c, and a commensurate (C) phase with a modulated period of 4c exists between the III and IV phases in the narrow temperature region (—58°C to —47°C on cooling), called the III' phase. The modulations in the IC phases are considered displacive type, but the detailed structures have not been studied. It is also not clear whether the modulation changes into periodic arrays of discommensurations (DC’s) near the III-III' and IV-V phase transition temperature as found in the ferroelectric materials such as Rb2ZnCl4.At room temperature (III phase) satellite reflections were seen around the fundamental reflections in a diffraction pattern (Fig.1) and they aligned along a certain direction deviated from the c* direction, which indicates that the modulation wave vector q tilts from the c* axis. The tilt angle is about 2 degree at room temperature and depends on temperature.

Sign in / Sign up

Export Citation Format

Share Document