Papers by Keyword: Ferroelectric

Abstract: The enhancement of ferroelectric and dielectric properties of PVDF-TrFE by incorporating various percentages of Magnesium Oxide (1 – 7%) for spin coated nanocomposite thin film was demonstrated. Observations showed uniform distribution and low agglomeration of MgO in the PVDF-TrFE nanocomposite thin film, especially for 3% MgO. Additionally, the 3% MgO incorporated into PVDF-TrFE had generated the highest P_r (88 mC/m²) and dielectric constant (13.6) in comparison other percentage compositions. However, the addition of more than 3% MgO filler loading caused a reduction in the ferroelectric and dielectric properties of the nanocomposite thin films.

Abstract: This research was conducted to improve the ferroelectric properties of PZT based ceramics by studying the effect of sintering conditions in terms of temperature and soaking time (time of sintering) on the ferroelectric properties of ceramics in the 0.8Pb (Zr_1/2Ti_1/2)O₃-0.2Pb (Zn_1/3Nb_2/3)O₃ system prepared by vibro-milling mixed-oxide method. The XRD patterns of specimens showed perovskite structure for all compositions. The pyrochlore phase was not observed in this system. The sintering temperature and soaking time affects the ferroelectric properties of ceramics by the optimum sintering condition for 0.8PZT-0.2PZN ceramic is sintered at 1250°C for 2h.

Abstract: In this study, Pb_0.91La_0.09(Zr_xTi_1-x)O₃ ceramics ( x = 0.75, 0.70, 0.65, 0.60, 0.55 and 0.50) have been synthesized by conventional mixed oxide method via a vibro-milling technique. The effect of composition on phase formation and electrical properties of PLZT ceramics was investigated. All compositions of powders were uniaxially pressed in pellets and sintered at the temperatures of 1275°C for 2h. Phase formation, dielectric, ferroelectric strain properties of ceramics were characterized by XRD, LCR meter, modified Sawyer–Tower Circuit and modified Michelson interferometric technique respectively. In this study new materials will be systematically developed based on the material engineering approach (processing vs electrical properties).

Abstract: Lead Free Ferroelectric Na_0.5Bi_0.5TiO₃ (NBT) Ceramic has been synthesized using sol gel method. The prepared NBT samples have been sintered at different temperatures 850°C, 950°C, 1050°C and 1150°C to achieve best sintering temperature. Structural analyses have been carried out using XRD and FTIR measurements. XRD patterns confirm perovskite structure having rhombohedral symmetry for all samples which is also supported by characteristic absorption band at ~627cm^-1 in FTIR spectra. Dielectric properties of NBT samples with frequency and temperature have been studied. NBT sample sintered at 1050°C exhibit comparatively high value of dielectric constant (ε’) and phase transition temperature (T_m). Ferroelectric properties of NBT samples have been studied at room temperature. Comparatively, better ferroelectric properties are observed for NBT sample having remnant polarization (P_r)~ 14.7 μC/cm²and coercive field (E_c)~ 26.8 kV/cm sintered at 1050°C.

Abstract: Barium strontium titanate (BST) materials with the chemical formula of Ba_xSr_1-xTiO₃ had successfully made ​​by solid state reaction method. The materials were made in the form of bulk. Ba mole composition was varied in the value of x = 0,5; 0,7; and 0,9. It was varied to study the influence on crystal structure and dielectric constant. The result of crystalline characterization performed by X-ray diffractometer instrument shows that changes in the composition of x causes a shift in the diffraction angle. The lattice parameter was obtained from the refinement with the GSAS software and calculation process. Lattice parameter of BST with a value of x = 0,5 and 0,7 are a = b = c, so that the crystal structure is cubic. While the BST with a value of x = 0,9 has lattice parameter a = b ≠ c, so that the crystal structure is tetragonal. Dielectric constant measurements performed at frequency of 1 KHz by RLC-meter instrument. The highest dielectric constant ​was ​obtained at 465 on Ba_0,9Sr_0,1TiO₃. The dielectric constant of cubic-crystal structured material is bigger than tetragonal-crystal structured material.

Abstract: On an example of poly(vinylidene fluoride - trifluorethylene) ferroelectric polymer we have shown how different optical methods can be applied for basic optical constants such as refractive index and absorption coefficient obtaining, scattering surface quality control, spectral transmission range control, examining polarization degree etc. Wide range of these methods can be applied not only to thin ferroelectric films but for other different samples.

Abstract: Ferroelectric superlattices with polarization perpendicular to the surface or interface are studied within the framework of the Landau-Ginzburg theory. An interface energy is introduced in the free energy to describe the effect of mixing and local polarization coupling at interface. Internal electric field is considered in the model. For superlattices grown on substrate, the influence of substrate on the properties of ferroelectric superlattices is required. This brief review is a sequel to the previous review article [1], which summarizes the recent development in Landau-Ginzburg theory developed for studying ferroelectric superlattices over approximately the last three years.

Abstract: Bismuth ferrite is an important material in ferroelectric photovoltaic field, because of its narrow band gap and large polarization. Doping is a common method to further improve the photovoltaic properties of bismuth ferrite. Mn-doped bismuth ferrite thin films were prepared by sol-gel method. The effects of manganese on the crystal structure, ferroelectric and photovoltaic properties have been investigated. The result indicates that Mn-doped bismuth ferrite thin films are single phase and the lattice constant increases with the increase of manganese content. As manganese content increases, the remnant polarization and coercive electric field increase, while the short circuit photocurrent density and power conversion efficiency decrease. The open circuit photovoltage increases first and reaches the maximum and then decreases as manganese content increases. The results indicate that enhanced ferroelectricity caused by addition of manganese doesn’t make improvement on the photovoltaic characteristic.

Abstract: The results of researches of polymer composite materials are given in this paper. The fillers of composites were: hexaferrite BaCo_0.7Zn_1.3Fe₁₆O₂₇; and BaTiO₃, CaTiO₃, Bi₄Ti₃O₁₂ were chosen as the ferroelectric components. Results of the researches of complex permittivity and permeability showed that composite of W-hexaferrite BaCo_0.7Zn_1.3Fe₁₆O₂₇ and CaTiO₃ had the best electromagnetic characteristics.

Abstract: The electrical properties of Tb₂O₃-doped bismuth titanate,Bi_4-xTb_xTi₃O₁₂ (BTT) ceramics prepared by a conventional electroceramic technique have been investigated. XRD analyses indicted Bi-layered perovskite structure in all samples, and revealed that Bi ions were only substituted near the Ti-O octahedron layers by Tb ions. SEM micrographs show randomly oriented and plate-like morphology. The remanent polarization ( P_r ) and coercive field ( E_c ) of the BTT ceramics with x=0.75 were above 16μC/cm² and 75KV/cm, respectively. The large value of remanent polarization and low coercive field of Tb-doped bismuth titanate ceramics promote these materials to potential applications.