Maxwell-Wagner Relaxation in Ca-, Sm- and Nd-doped Ceria
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Doped ceria, i.e.Ce1-xMxO2-with M being dopant metal, has been a focus of great attention for solid oxide fuel cells (SOFCs) due to their high oxygen conduction.In the past literature, the dielectric relaxations in these materials have been ascribed to be caused by defect associates (MCeʺ-V̈) possessing different MCeʺ and V̈ distances.But we believe that with changing measurement and analysis techniques, it is necessary to invest our time to re-examine the already reported materials and take a detailed investigation of the underlying phenomenon behind their dielectric relaxations again.Thus, we have used solid-state reaction to prepare Ce1-xMxO2- with M=Ca, Sm, and Nd in x=0.1, 0.2, and 0.3 ratios, respectively.The as-prepared and post annealed samples were tested for dielectric properties from 300-1080 K with varying frequencies.The lowtemperature relaxation (R1) was argued to be a Maxwell-Wagner relaxation caused by humidity sensitivity.The hightemperature relaxation (R2) was ascribed to be caused by the hopping motion of oxygen vacancies.This fact was also supported by a detailed analysis of impedance spectra.While according to the previous reports, this relaxation is because of the oxygen-vacancy-dopant defect pair.Keywords:
Dielectric loss
Cole–Cole equation
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Novel polymer-based composites with high dielectric constant and low dielectric loss were prepared by simply mixing polyvinylidene fluoride (PVDF) with semiconductor vanadium pentoxide (V2O5) filler. V2O5 nanobelts with diameter around 50 nm and length up to micrometer scale were uniformly distributed in PVDF matrix without serious aggregation. The PVDF/V2O5 composites show excellent dielectric properties. When the volume fraction of V2O5 is 0.15 and the frequency is 100 Hz, the dielectric constant of the composites can reach as high as 140 and the dielectric loss is 0.7. Both dielectric constant and dielectric loss of the composites show but sharp increase when the volume fraction of V2O5 is above 0.15. Furthermore, the dependences of the dielectric constant and dielectric loss on frequency were also studied. With the increase of frequency from 102 to 107 Hz, dielectric constant of the PVDF/V2O5 composites decreases, while the dielectric loss increases slightly. The results indicate that the PVDF/V2O5 composites are promising materials for capacitors.
Polyvinylidene fluoride
Dielectric loss
High-κ dielectric
Volume fraction
Pentoxide
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This project studied the effect of MgTi03 (MT) addition on CaCu3Ti40i2 (CCTO). Recently an oxide ceramic CCTO was reported that exhibits very high dielectric constant value, which is desirable for many microelectric applications. However, the dielectric loss of the material is relatively and become less useable. Therefore, in this work, CCTO is doped with MT in order to lower the dielectric loss. The MT-doped CCTO was prepared by using solid state reaction method. The MT doped with CCTO, calcining at 1000°C for 12 hours and sintered at 1100°C for 24 hours. Effect of MT dopant to the dielectric properties of CCTO had been studied. The high dielectric constant and low dielectric loss was observed at 0.1, and 0.2 MT dopant compared from its pure samples (X= 0). However for 0.3 MT dopant was dropped from high value of dielectric constant to the lowest value and result in high dielectric loss. Over the wide frequency range, 0.1 MT was more stable then other samples that always present high dielectric constant and low dielectric constant compared with undoped CCTO and other sample. This result indicates that certain MT dopant can be used to improve the dielectric properties of CCTO.
Dielectric loss
High-κ dielectric
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Dielectric loss
Thermal Stability
High-κ dielectric
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Dielectric loss
Diffractometer
High-κ dielectric
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Dielectric loss
Thermal Stability
High-κ dielectric
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A new A site complex lead-free ferroelectric ceramics of(1-x-y)BNT-xBKT-yBiCoO3 was prepared by a conventional ceramic sintering technique.The relation between composition and dielectric properties,dielectric properties and frequency were investigated.It was found that the dielectric constant and dielectric loss of unpoled samples is higher that those of poled samples.The dielectric constant and dielectric loss of unpoled samples decrease with the increase content of BiCoO3.The dielectric constant and dielectric loss of unpoled and poled samples increase with the content of BKT increasing.The dielectric constant decreases with frequency increasing,and the decreasing trend become slowly.The dielectric loss first decrease and then increase with increasing frequency.
Dielectric loss
Ferroelectric ceramics
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The Ba(Zr0.2Ti0.8)O3 ceramics were prepared using BaCO3,ZrO2 and TiO2 et al as crude materials,Sm2O3 as dopant,and the dielectric properties are investigated.The morphology of the samples was observed by SEM.It was found that the Sm3+ ions tended to enter into the B-site in the perovskit lattice with the amount of the dopants increase when the amount of x(Sm2O3) was less than 0.2% and after the Sm3+ ions entered into the A-site.The amount of Sm2O3-dopant has significantly influence on the dielectric constant and the loss of the sample.When the amount of x(Sm2O3) was 0.2%,the ceramic sample had the maximum dielectric constant of about 5 600.With the amount of Sm2O3-dopant increase,the dielectric loss of the sample has been improved significantly and the minimum loss has decreased to 0.002 1.
Dielectric loss
Lattice constant
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Dielectric loss
Atmospheric temperature range
High-κ dielectric
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The dielectric relaxation of a model solution of polydisperse rods is studied numerically, using a modified Doi-Edwards model. A new model of the dielectric relaxation in the biphasic range of concentration is proposed.
Cole–Cole equation
Rod
Dynamics
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