A study of the dielectric properties of PZT and PT ceramics depending on the lattice distortion

2005 ◽  
Vol 83 (5) ◽  
pp. 527-540 ◽  
Author(s):  
Duan -Ming Zhang ◽  
Xiang -Yun Han ◽  
Zhi -Hua Li ◽  
Zhi -Cheng Zhong ◽  
Wen -Sheng Yan ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Lattice Distortion ◽  
Volume Fraction ◽  
Structural Phase ◽  
Rhombohedral Phase ◽  
Point Of View ◽  
Distribution Model ◽  
Coexistence Region ◽  
Pzt Ceramics ◽  
Lattice Distortions

Depending on the lattice distortion, the dielectric properties of PZT and PT ceramics are studied from a structural phase transition point of view. The study involves a more profound physical process than the study of the relation between the dielectric properties and composition x. Two equations connecting the dielectric properties and the lattice distortions are established in the tetragonal and rhombohedral phase regions. In particular, the relation between the dielectric properties and the lattice distortion is investigated in the phase coexistence region of PZT ceramics using a phase statistical distribution model, and we determine the fitting value of the volume fraction of the tetragonal phase VT to composition x in the equation. All the fitting results indicate that our results are very consistent with the related experimental data for PZT and PT ceramics.PACS Nos.: 64.70.–p, 77.22.–d, 77.84.–s

Dielectric Properties and Lattice Distortion in Rhombohedral Phase Region and Phase Coexistence Region of PZT Ceramics

2005 ◽  
Vol 43 (5) ◽  
pp. 855-860 ◽  
Author(s):  
Zhang Duan-Ming ◽  
Zhong Zhi-Cheng ◽  
Han Xiang-Yun ◽  
Yan Wen-Sheng ◽  
Sun Hong-Zhang ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Lattice Distortion ◽  
Rhombohedral Phase ◽  
Phase Region ◽  
Phase Coexistence ◽  
Coexistence Region ◽  
Pzt Ceramics

scholarly journals Effect of Terminal Groups on Thermomechanical and Dielectric Properties of Silica–Epoxy Composite Modified by Hyperbranched Polyester

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2451
Author(s):  
Jianwen Zhang ◽  
Dongwei Wang ◽  
Lujia Wang ◽  
Wanwan Zuo ◽  
Lijun Zhou ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Binding Energy ◽  
Epoxy Resin ◽  
Volume Fraction ◽  
Epoxy Composite ◽  
Mean Square Displacement ◽  
Mean Square ◽  
Hyperbranched Polyester ◽  
Free Volume Fraction

To study the effect of hyperbranched polyester with different kinds of terminal groups on the thermomechanical and dielectric properties of silica–epoxy resin composite, a molecular dynamics simulation method was utilized. Pure epoxy resin and four groups of silica–epoxy resin composites were established, where the silica surface was hydrogenated, grafted with silane coupling agents, and grafted with hyperbranched polyester with terminal carboxyl and terminal hydroxyl, respectively. Then the thermal conductivity, glass transition temperature, elastic modulus, dielectric constant, free volume fraction, mean square displacement, hydrogen bonds, and binding energy of the five models were calculated. The results showed that the hyperbranched polyester significantly improved the thermomechanical and dielectric properties of the silica–epoxy composites compared with other surface treatments, and the terminal groups had an obvious effect on the enhancement effect. Among them, epoxy composite modified by the hyperbranched polyester with terminal carboxy exhibited the best thermomechanical properties and lowest dielectric constant. Our analysis of the microstructure found that the two systems grafted with hyperbranched polyester had a smaller free volume fraction (FFV) and mean square displacement (MSD), and the larger number of hydrogen bonds and greater binding energy, indicating that weaker strength of molecular segments motion and stronger interfacial bonding between silica and epoxy resin matrix were the reasons for the enhancement of the thermomechanical and dielectric properties.

scholarly journals Insulation Characteristics of Sisal Fibre/Epoxy Composites

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
A. Shalwan ◽  
M. Alajmi ◽  
A. Alajmi
Keyword(s):  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Thermal Characteristics ◽  
Fibre Volume ◽  
Point Of View ◽  
Natural Fibres ◽  
Epoxy Composites ◽  
Ongoing Research ◽  
Sisal Fibre ◽  
The Impact

Using natural fibres in civil engineering is the aim of many industrial and academics sectors to overcome the impact of synthetic fibres on environments. One of the potential applications of natural fibres composites is to be implemented in insulation components. Thermal behaviour of polymer composites based on natural fibres is recent ongoing research. In this article, thermal characteristics of sisal fibre reinforced epoxy composites are evaluated for treated and untreated fibres considering different volume fractions of 0–30%. The results revealed that the increase in the fibre volume fraction increased the insulation performance of the composites for both treated and untreated fibres. More than 200% insulation rate was achieved at the volume fraction of 20% of treated sisal fibres. Untreated fibres showed about 400% insulation rate; however, it is not recommended to use untreated fibres from mechanical point of view. The results indicated that there is potential of using the developed composites for insulation purposes.

Modeling The Microwave Frequency Dielectric Properties of Thermoplastic Composite Materials

1992 ◽  
Vol 269 ◽  
Author(s):  
Mitchell L. Jackson ◽  
Curtis H. Stern
Keyword(s):  
Composite Materials ◽  
Dielectric Properties ◽  
Volume Fraction ◽  
Perturbation Technique ◽  
Resonant Cavity ◽  
Microwave Frequency ◽  
Thermoplastic Composite ◽  
Fiber Volume ◽  
Thermoplastic Matrix ◽  
Rotation Procedure

ABSTRACTMixture models were studied in an effort to predict the microwave frequency permittivities of unidirectional-fiber-reinforced thermoplastic-matrix composite materials as a function of fiber volume fraction, fiber orientation relative to the electric field, and temperature. The permittivities of the constituent fiber and plastic materials were measured using a resonant cavity perturbation technique at 9.4 GHz and at 2.45 GHz. The permittivities of the composite specimens were measured using a reflection cavity technique at 9.4 GHz and at 2.45 GHz. Simple “rule-of-mixtures” models that use the fiber and plastic permittivities have been found to approximate the complex dielectric properties of the composite for varied fiber volume fractions. The permittivities of oriented composites were modeled using a tensor rotation procedure. Composite permittivities were modeled with temperature up to the glass transition temperature of the thermoplastic matrix.

High Strength Conductors and Structural Materials for High Field Magnets

MRS Advances ◽  
2016 ◽  
Vol 1 (17) ◽  
pp. 1233-1239 ◽  
Author(s):  
Ke Han ◽  
Rongmei Niu ◽  
Jun Lu ◽  
Vince Toplosky
Keyword(s):  
Service Life ◽  
High Field ◽  
Lattice Distortion ◽  
Mechanical Load ◽  
Cold Deformation ◽  
High Strength ◽  
Structural Support ◽  
Metal Metal ◽  
Lattice Distortions ◽  
Materials Used

ABSTRACTOne important approach to increasing High magnetic fields (HMF) beyond what is now possible is to improve the properties of various composite materials used as both conductors and structural support. Typical conductors for high field magnets are Cu-based metal-metal composites. To achieve high mechanical strength, these composites are fabricated by cold deformation, which introduces high densities of interfaces along with lattice distortions. During the operation of a magnet, mechanical load, high magnetic field, extreme temperatures and other stressors are imposed on the materials, causing them to be further “processed”. The composite conductors in a magnet, for example, may undergo high temperatures, which reduce lattice distortions or soften the material. At the same time, HMF may increase lattice distortion, leading to a complex change in interface characteristics. Both the mechanical properties of the conductors, like the tensile and yield strength, and the electric conductivity of the composites are closely connected to changes in lattice distortion and interface density. Understanding these changes helps us to assure that materials can operate in optimized conditions during most of magnets’ service life. Maximizing service life is critical, given the high cost of building and operating high field magnets. The goal of this paper is to 1) show our understanding of changes that occur in the properties of selected materials during the fabrication and under HMF and 2) to discuss how those changes relate to the microstructure of these materials and consequently to the service life of high field magnets.

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