A Modular Approach to Ferroelectric Polymers with Chemically Tunable Curie Temperatures and Dielectric Constants

2006 ◽  
Vol 128 (25) ◽  
pp. 8120-8121 ◽  
Author(s):  
Yingying Lu ◽  
Jason Claude ◽  
Bret Neese ◽  
Qiming Zhang ◽  
Qing Wang
Keyword(s):  
Dielectric Constants ◽  
Modular Approach ◽  
Ferroelectric Polymers ◽  
Curie Temperatures

The Characteristics of Ferroelectric Sr0.4Ba0.6Nb2-xVxO6 Dielectrics

2008 ◽  
Vol 368-372 ◽  
pp. 136-139
Author(s):  
Yao Sheng Yang ◽  
Wen Cheng Tzou ◽  
Guan Hung Wu ◽  
Cheng Fu Yang ◽  
Chern Hwa Chen ◽  
...  
Keyword(s):  
Ceramic Material ◽  
Sintering Temperature ◽  
Dielectric Constants ◽  
Temperature Dependent ◽  
Dielectric Characteristics ◽  
Sem Micrographs ◽  
V2o5 Content ◽  
Large Influence ◽  
Curie Temperatures

In this study, it would be interesting to investigate ceramic material based on Sr0.4Ba0.6Nb2O6 composition, V2O5 was used to substitute Nb2O5 to form the compositions of Sr0.4Ba0.6Nb2-xVxO6, where 0 ≤ x ≤ 0.3. The prepared Sr0.4Ba0.6Nb2-xVxO6 ceramics were sintered from 1060oC to 1300oC, and the needed sintering temperatures were dependent on V2O5 content. The SEM micrographs showed that even 1220oC was used as the sintering temperature of Sr0.4Ba0.6Nb2O6 ceramics, the pores were still observed. The crystal intensities of some (h,k,l) planes, for example (3,2,0) and (5,5,0) planes, apparently increased with the increase of V2O5 content and slightly decreased with the increase of sintering temperatures. The temperature-dependent dielectric characteristics were measured from 25oC to 300oC at 1MHz as a function of sintering temperatures and V2O5 content. The studied results would show that the sintering temperatures and V2O5 content also had large influence on the maximum dielectric constants (revealed at Curie temperatures) and the temperature-dielectric curves of Sr0.4Ba0.6Nb2-xVxO6 ceramics.

Effect of A-site vacancy order-disorder states on diffuse phase transition of the morphotropic phase boundary Pb1−xBaxNb2O6 ferroelectrics

1996 ◽  
Vol 11 (9) ◽  
pp. 2302-2308 ◽  
Author(s):  
Xiaoyue Xiao ◽  
Yan Xu ◽  
Zhigang Zeng ◽  
Zhilun Gui ◽  
Longtu Li ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Boundary ◽  
Morphotropic Phase Boundary ◽  
Diffuse Phase Transition ◽  
Frequency Dispersion ◽  
Dielectric Constants ◽  
A Site ◽  
Curie Temperatures ◽  
Site Vacancy ◽  
Diffuse Phase

The effect of A-site vacancy order-disorder states on diffuse phase transition (DPT) of tungsten bronze Pb1−xBaxNb2O6 (PBN) ferroelectrics has been investigated. The A-site vacancy disordered PBN ceramics exhibit notable variations of the Curie temperatures (i.e., the temperatures at the dielectric maximum permittivities) up to 12 °C in response to frequency changed from 0.1 KHz to 100 KHz. The largest frequency dispersion occurred at the morphotropic phase boundary of 1 − X = 0.63, along with the lowest Curie point. In contrast, the A-site vacancy ordered PBN ceramics present little frequency dispersion in the range of 2 °C from 0.1 KHz to 100 KHz. Dielectric constants of the disordered PBN ceramics were generally higher than those of the ordered ones. In comparison with the ordered PBN ceramics, the Curie points of the disordered ceramics were shifted from lower to higher temperature as the Pb2+ cation percentage was decreased; i.e., the Curie temperatures of the disordered PBN ceramics were lower than those of the ordered ones when 1 − X ≥ 0.70, but higher when 1 − X ≤ 0.65. These differences are suggested to inherently result from the A-site vacancy order-disorder states. The relationship between the A-site vacancy order-disorder states and the dielectric properties has also been confirmed with studies of thermal hysteresis.

Effects of dopants on PbO–MgO–Nb2O5 ceramics near the Pb(Mg⅓Nb⅔)O3 composition

1989 ◽  
Vol 4 (4) ◽  
pp. 945-966 ◽  
Author(s):  
M. F. Yan ◽  
H. C. Ling ◽  
W. W. Rhodes
Keyword(s):  
Manganese Oxides ◽  
Relative Effectiveness ◽  
Dissipation Factor ◽  
Dielectric Constants ◽  
Quaternary Systems ◽  
Rates Of Change ◽  
Electrical Resistivities ◽  
Bond Strengths ◽  
Device Properties ◽  
Curie Temperatures

We studied the effects of 15 dopants on the dielectric properties of the Pb1–x–yMgxNb2yO1+4y perovskite system. The investigated dopants are Ba, Ag, La, Bi, and Nd, which substitute in the Pb sublattice, and Co, Ni, Zn, Mn, Cr, Dy, Al, Fe, Zr, and Ti, which substitute in the sublattice occupied by Mg and Nb. While the dielectric constants of Pb1−x–yMgxNb2yO1+4y) are not affected by Al, Zr, and Ni dopants, their dielectric constants are increased by Ti dopant and decreased by other dopants. The rates of change in the Curie temperatures of Pb1–x–y MgxNb2yO1+4y with different dopant concentrations were quantitatively measured. The relative effectiveness of these dopants in altering the Curie temperature is correlated to the bond strengths between oxygen and the dopants in either the Pb sublattice or the Mg/Nb sublattice. The effects of these dopants on the dissipation factors and electrical resistivities were investigated. Cobalt and manganese oxides were identified as the most effective dopants in reducing the dissipation factor and lanthanum and barium oxides are effective in increasing the resistivity. We have also observed that zinc oxide promotes densification and reduces the temperature coefficient of capacitance in these compositions. Ternary and quaternary systems based on selected combinations of these dopants were prepared and characterized. Compositions in the Pb(Zn⅓Nb⅔)O3 + Pb(Co⅓Nb⅔O3 + PbTiO3 + Pb1–x–yMgxNb2yO1+4y quaternary systems were shown to be promising candidates for capacitor applications. Furthermore, multilayer capacitors of these promising compositions were fabricated and they were shown to have favorable device properties.

Influence of Excess Bi2O3 on the Characteristics of (Na0.5Bi0.5)TiO3-BaTiO3 Ceramics

2008 ◽  
Vol 368-372 ◽  
pp. 65-68 ◽  
Author(s):  
Yin Fang Wei ◽  
Chia Hsiung Kao ◽  
Cheng Fu Yang ◽  
Ho Hua Chung ◽  
Hong Hsin Huang ◽  
...  
Keyword(s):  
Piezoelectric Materials ◽  
Dielectric Constants ◽  
Sintering Process ◽  
Dielectric Characteristics ◽  
Temperature Range ◽  
Measured Frequency ◽  
Sintering Characteristics ◽  
Xrd Patterns ◽  
Curie Temperatures ◽  
Bi2o3 Content

In this study, piezoelectric materials 0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 (NBT-BT) composition with excess x wt% Bi2O3 (x=0, 1, 2, and 3) are investigated as a function of sintering temperatures. The sintering characteristics and dielectric characteristics of excess Bi2O3-doped 0.95 (Na0.5Bi0.5)TiO3- 0.05 BaTiO3 ceramics are developed with the aid of SEM, XRD patterns, and dielectric-temperature curves. The sintering process is carried out in air for 2h from 1120oC to 1200oC. Dielectric-temperature properties are investigated in the temperature range of 30oC~350oC at the frequencies of 10KHz~1MHz. The maximum dielectric constants of NBT-BT ceramics first increase with the increase of Bi2O3 content, reach the maximum at 1wt%- Bi2O3-added NBT-BT ceramics, and then decrease with the further increase of Bi2O3 content. The maximum dielectric constants of NBT-BT ceramics are almost unchanged as the measured frequency increases. The Curie temperatures of NBT-BT ceramics are also developed.

Ferroelectric Polymers with Chemically Tunable Dielectric Constants

2006 ◽  
Vol 949 ◽  
Author(s):  
Yingying Lu ◽  
Jason Claude ◽  
Kun Li ◽  
Qiming Zhang ◽  
Qing Wang
Keyword(s):  
Vinylidene Fluoride ◽  
Structural Characteristics ◽  
Hydrogenation Reaction ◽  
Dielectric Constants ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Thermal Transitions ◽  
Ferroelectric Polymers ◽  
Poly Vinylidene Fluoride ◽  
High Dielectric

ABSTRACTWe present a modular approach toward poly(vinylidene fluoride) based ferroelectric polymers with high dielectric constants and energy densities. This strategy is based on a two-step reaction including the co-polymerization of vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) and a subsequent hydrogenation reaction. Due to the similar reactivity of VDF and CTFE in free radical polymerization and quantitative yield of dechlorination reaction, the chemical compositions of the resulting terpolymers can be precisely controlled, leading to tunable Curie temperatures and dielectric constants. A library of the ferroelectric polymers with dielectric constants varying from 11 to 50 measured at 1 kHz and room temperature has been prepared. The structural characteristics including microstructure, chain conformation, and crystallinity of the polymers have been carefully elucidated as a function of the chemical composition by 1H and 19F NMR, Fourier transform infrared spectroscopy, and wide angle X-ray diffraction. The influence of the polymer compositions on thermal transitions and dielectric constants has also been investigated.

Sintering and Dielectric Properties of Excess Bi2O3 Doped BaBi2Nb2O9 Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 188-191 ◽  
Author(s):  
Ho Hua Chung ◽  
Cheng Fu Yang ◽  
Yi Chang Chung ◽  
Cheng Yuan Kung
Keyword(s):  
Dielectric Properties ◽  
Sintering Temperature ◽  
Ferroelectric Materials ◽  
Dielectric Constants ◽  
X Ray Diffraction ◽  
Dielectric Characteristics ◽  
X Ray ◽  
Curie Temperatures ◽  
Bi2o3 Content ◽  
Apparent Influence

In this study, ferroelectric materials with Bi-layered structure BaBi2Nb2O9 with excess x wt% Bi2O3 (x=0, 1.5, and 3) are investigated as the main compositions, and the sintering is proceeded from 1000oC~1100oC. The effect of Bi2O3 on the morphologies, crystal structure, and dielectric characteristics of BaBi2Nb2O9 ceramics is developed with the aid of SEM, X-ray diffraction, and dielectric-temperature curves. Dielectric properties are investigated in the temperature of 25oC~ 465oC at frequency 10KHz~1MHz. It is found that sintering temperature and Bi2O3 content has no apparent influence on the Curie temperatures, but they have large influence on the maximum dielectric constants.

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