Ferroelectric properties and breakdown strength of layer-by-layer poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and polyurethane (PU) for energy storage application

Ferroelectric polymers are one of the next- generation pulsed capacitor materials for the potential application in capacitive energy storage. This polymer with higher saturated polarization, smaller remnant polarization, and higher electrical breakdown are the most promising candidates. In this work, the dielectric properties and energy storage capacity of the bilayer polymer films of Poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and polyurethane (PU) were studied. These bilayer polymers were prepared by layer- by- layer method at the condition of variable layer thickness. The results show that the dielectric constants and the saturated polarization of the bilayer films increased, and bilayer films with P70/PU30 exhibit electrical high breakdown strength up to 379 V/μm. Moreover, enhanced energy storage density and the energy efficiency of the bilayer constrictors will be discussed for the capacitive energy storage polymers.

Influence of Synthesis-Related Microstructural Features on the Electrocaloric Effect for 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 Ceramics

Despite having a very similar electrocaloric (EC) coefficient, i.e., the EC temperature change divided by the applied electric field, the 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 (PMN-10PT) ceramic prepared by mechanochemical synthesis exhibits a much higher EC temperature change than the columbite-derived version, i.e., 2.37 °C at 107 °C and 115 kV/cm. The difference is due to the almost two-times-higher breakdown field of the former material, 115 kV/cm, as opposed to 57 kV/cm in the latter. While both ceramic materials have similarly high relative densities and grain sizes (>96%, ≈5 μm) and an almost correct perovskite stoichiometry, the mechanochemical synthesis contributes to a lower level of compositional deviation. The peak permittivity and saturated polarization are slightly higher and the domain structure is finer in the mechanochemically derived ceramic. The secondary phases that result from each synthesis are identified and related to different interactions of the individual materials with the electric field: an intergranular lead-silicate-based phase in the columbite-derived PMN-10PT and MgO inclusions in the mechanochemically derived ceramic.

Multi-Ferroic Properties on BiFeO3/BaTiO3 Multi-Layer Thin-Film Structures with the Strong Magneto-Electric Effect for the Application of Magneto-Electric Devices

The characteristics of X-ray Diffraction (XRD), Current (I)-Voltage (V), and the Polarization-Electric field (P-E) on the BiFeO3 (BFO), BaTiO3 (BTO), and our proposed Multi-Layer (ML) BiFeO3/BaTiO3 (BFO/BTO) samples are studied systemically. The influence of these films with and without different external Magnetic (Mex.) inputs is also investigated. Our proposed multi-ferroic ML BFO/BTO sample has a lower tunneling current (Jg) (~5 × 103 times) and a stronger magneto-electric effect (an ~25 times higher value of the change of saturated polarization Ps with the Mex. inputs than the pure multi-ferroic BFO sample. The material properties for ML BFO/BTO samples can be optimized with the combination of the advantages of BFO and BTO thin films. The stronger magneto-electric effect in our proposed ML samples can have many applications such as magnetic sensors, magnetic electric devices, and logic Magneto-Electric Spin–Orbit (MESO) devices.

Conductive-perovskite LaNiO3 thin films prepared by using solution process for electrode application

Lanthanum nickel oxide LaNiO3 (LNO) is extensively known as one of typical perovskite-structured materials with metallic conductivity, which is suitable for the electrode application in electronic devices such as transistors or solar cells. Since LNO is a low-cost material and a simple fabrication process, it has been attracted much attention for commercialization. In this paper, we have focused on optimizing the fabrication process of LNO thin films on SiO2/Si substrate and Al foil by using a solution process. The crystal structure and surface morphology were characterized by using X-ray diffraction and field-emission scanning electron microscopy (FE-SEM), respectively. It was found that the LNO thin films annealed in range of 550-700oC for 30 min exhibited a well-formed crystallization and a dense microstructure. According to the SEM cross-sectional observation, the thickness of LNO thin films was estimated about 80 nm. Also, from the four-probe measurement method, the electrical resistivity of LNO thin film annealed at 600oC had a minimum value of 0.42 × 10-2 Ωcm, which was possibly comparable to conventional conductive oxides. As a result, the capacitor using Pb1.2(Zr0.4Ti0.6)O3 ferroelectric layer annealed at 600oC and LNO bottom electrode provided an interesting ferroelectricity, which included a remnant polarization of 21 µC/cm2 and a saturated polarization of 35 µC/cm2. Moreover, the leakage current density was lower than 2 × 10-5 A/cm2.

Synthesis of PVDF/SBT composite thin films by spin coating technology and their ferroelectric properties

Ferroelectric composite thin films of x-SBT/PVDF with different SBT content (weight ratios of SBT to PVDF, x = 0 %, 5 %, 10 %, 15 %, 20 %) were prepared by spin-coating method. The crystal structures of x-SBT/PVDF films were analyzed by X-ray diffraction (XRD) measurements and Fourier transform-infrared spectroscopy (FT-IR), respectively. Experimental results demonstrated that both α, β-phases PVDF and the layered perovskite SBT co-existed in the x-SBT/PVDF samples. With an increase of SBT content in the x-SBT/PVDF thin films, both the dielectric constant and the saturated polarization were also increased, compared with those of pure PVDF thin film. More importantly, when the SBT content in the x-SBT/PVDF thin films was larger than 15 %, the coercive field of x-SBT/PVDF thin films was also decreased.

Molecular Dynamics Simulations of Piezoelectric Materials for Energy Harvesting Applications

The previously proposed polarizable charge equilibrium (PQEq) force field model is parameterized for studying lead titanate (PT), lead zirconate (PZ), and their alloys: lead zirconate titanate (PZT). Several molecular dynamics (MD) simulations are performed to assess the degree of accuracy of the model. The phase transition temperatures, which are generally inaccurate in MD, are shown to be similar to experimental measurements. Also, the calculation of the ferroelectric hysteretic behavior, including the spontaneous polarization, saturated polarization and coercive fields, with extended MD is shown to give a qualitatively correct comparison between PT and PZT. The accuracy of the electronic properties in PQEq leads to direct application to a range of interesting problems such as enhanced properties of piezo- and ferro-electric nanostructures and the kinetics of domain walls in these materials.

Effect of Sb Substitution on the Crystal Structure and Multiferroic Properties of BiFeO3

The single-phase multiferroic Bi1-xSbxFeO3 ceramics were fabricated using traditional solid phase reaction technique and the effects of Sb3+ doping on their crystal structure and ferroelectric behavior were studied. X-ray diffraction (XRD) measurement revealed that 830°C is an appropriate sintering temperature for forming a pure-phase of Bismuth ferrite structure. The average crystalline grain size of doped ceramics becomes smaller as the doping concentration x increases. The leakage current of doped sample was much reduced compared with that of BFO. The electric hysteresis loops were obtained in the Bi1-xSbxFeO3 (x=0.02), and the residual polarization and saturated polarization are 0.03 μC/cm2 and 0.337 μC/cm2, respectively.

Characteristics of BiFeO3 Thin Films on a LaAlO3 Substrate by RF Sputtering

In this paper, BiFeO3 (BFO) films were grown on LaAlO3 (LAO) substrate by a RF magnetron sputtering system. Fabrication parameters, such as work pressure, sputtering atmosphere, and post annealing were examined in terms of their influences on characteristics of the ferroelectric films. X-Ray diffraction, Raman scattering and scanning electron microscope measurements were employed to characterize the microstructure and the morphology of these films. At last, the ferroelectric characteristic of BFO has been studied, and the film has a large saturated polarization of 40 μC / cm2 under an applied field of 12 kV /cm.