In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).

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A review of electrode materials for electrochemical supercapacitors

Multiferroic materials, which show simultaneous ferroelectric and magnetic ordering, exhibit unusual physical properties — and in turn promise new device applications — as a result of the coupling between their dual order parameters. We review recent progress in the growth, characterization and understanding of thin-film multiferroics. The availability of high-quality thin-film multiferroics makes it easier to tailor their properties through epitaxial strain, atomic-level engineering of chemistry and interfacial coupling, and is a prerequisite for their incorporation into practical devices. We discuss novel device paradigms based on magnetoelectric coupling, and outline the key scientific challenges in the field.

Multiferroics: progress and prospects in thin films.

In this review, the technologies and working principles of different materials used in supercapacitors are explained. The most important supercapacitor active materials are discussed from both research and application perspectives, together with brief explanations of their properties, such as specific surface area and capacitance values. A review of different supercapacitor electrolytes is given and their positive and negative features are discussed. Finally, cell configurations are considered, pointing out the advantages and drawbacks of each configuration.

Review on supercapacitors: Technologies and materials

An overview of the state of art in ferroelectric thin films is presented. First, we review applications: microsystems' applications, applications in high frequency electronics, and memories based on ferroelectric materials. The second section deals with materials, structure (domains, in particular), and size effects. Properties of thin films that are important for applications are then addressed: polarization reversal and properties related to the reliability of ferroelectric memories, piezoelectric nonlinearity of ferroelectric films which is relevant to microsystems' applications, and permittivity and loss in ferroelectric films-important in all applications and essential in high frequency devices. In the context of properties we also discuss nanoscale probing of ferroelectrics. Finally, we comment on two important emerging topics: multiferroic materials and ferroelectric one-dimensional nanostructures. (c) 2006 American Institute of Physics.

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Ferroelectric thin films: Review of materials, properties, and applications

In the laser treatment of a workpiece (9), e.g. for surface hardening, melting, alloying, cladding, welding or cutting, the adverse effect of reflectivity of the surface, when a pure, monochromatic laser (6) is used, is remedied by the simultaneous application of a relatively shorter wavelength beam (1). The two beams (1)(5) may be combined by a beam coupler (4) or may reach the workpiece (9) by separate optical paths (not shown). The shorter wavelength beam (1) improves the coupling efficiency of the higher- powered laser beam (5).

Laser Material Processing

High‐temperature‐superconductor Josephson junctions with an edge geometry of superconductor/normal‐metal/superconductor have been fabricated on yttria‐stabilized zirconia substrates by engineering the electrode and N‐layer material to reduce the lattice mismatches (a, b, and c). With GdBa2Cu3O7−δ as electrodes and Pr‐doped Y0.6Pr0.4Ba2Cu3O7−δ as a barrier, the lattice mismatches from electrode and barrier layer are reduced to a very low level. The junctions fabricated with such a design demonstrate resistively shunted junction current‐voltage characteristics under dc bias at temperatures in the range of 77–88 K. The quite low specific interface resistivity on the order of 10−10 Ω cm2 indicates that the junction performance is controlled by the normal‐metal (N) layer material instead of the interfaces. The use of lattice‐matched electrode and N‐layer material is one of the key design rules to obtain controllable high‐temperature superconductor Josephson junctions.

Superconductor GdBa2Cu3O7−δ edge junctions with lattice‐matched Y0.6Pr0.4Ba2Cu3O7−δ barriers

Regrowth of ion-damaged YBa{sub 2}Cu{sub 3}O{sub 7{minus}}{sub {delta}} thin films on LaAlO{sub 3} was studied using the ion beam channeling technique. The damaged films can be regrown at a temperature as low as 650 {degree}C, and are stable up to 1000 {degree}C. The regrowth process was found to be thermally activated with a single activation energy of 0.46 eV, contrary to two energies found in a previous study on the films on MgO (J. A. Martinez {ital et} {ital al}., Appl. Phys. Lett. {bold 57}, 189 (1990)).

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400015697

Thermal regrowth of ion-damaged YBa2Cu3O7−δ superconducting thin films

Ion Beam Assisted Deposition (IBAD) of Magnesium Oxide (MgO) has been proven to be a viable route for producing template films used to deposit high quality YBCO coated conductors on flexible polycrystalline metal substrates. Here we will discuss improvements in this process using a dual ion assist beam configuration. Dual ion assist beam deposition of MgO reduces the requirements for substrate surface finishing while maintaining comparable film quality (phi scan full‐width at half‐maximum values between 7 and 8 degrees). Furthermore, this adaptation of the IBAD process eliminates the degradation of MgO texture observed in thick IBAD MgO films deposited on silicon nitride. We have deposited films up to 50 nanometers thick without degradation of in‐plane texture. Increasing the MgO thickness increases the chemical stability of the template layer and can eliminate the necessity for subsequent buffer layers or the application of the homoepitaxial MgO layer needed to stabilize the thin, conventional IBAD MgO layer. Initial results of subsequently deposited YBCO on these dual assist ion beam MgO templates are quite promising.

Dual Ion Assist Beam Deposition of Magnesium Oxide for Coated Conductors

We present a comparative study of the flux pinning properties of YBa{sub 2}Cu{sub 3}O{sub 7} films deposited by pulsed laser deposition on polycrystalline metal substrates with a biaxially oriented MgO template produced by ion-beam-assisted deposition (IBAD), varying the deposition temperature (T{sub STO}) for the SrTiO{sub 3} buffer layer. We find that when T{sub STO} = T*{sub STO} = 820 C, the critical current density at self-field (J{sub c}{sup sf}) is maximized and the surface roughness minimized. On the contrary, in-field critical current density (J{sub c}) measurements show that at high fields, samples with T{sub STO} <T*{sub STO} present higher J{sub c}. Angular-dependent J{sub c} measurements show that this improvement is due to the presence of additional extended parallel defects (in particular, thread dislocations), which produce a peak in J{sub c} centered in the c-axis direction. We use the field dependence of the height and the width of this peak to compare the density of the correlated defects in samples prepared with different T{sub STO}.

Improving flux pinning in YBa[sub 2]Cu[sub 3]O[sub 7] coated conductors by changing the buffer layer deposition conditions

). We report results on HLPE YBCO films grown on (100) strontium titanate and textured technical substrates such as rolling-assisted biaxially textured substrates (RABiTS) and ion-beam-assisted-deposited (IBAD) MgO. High values of the critical temperature above 90 K and critical current 400 A per cm width for 3 thick films on single crystal substrates and promising high values on technical substrates are obtained. Furthermore, there is potential for making thicker films of the same quality since film density is maintained with thickness. Angular-dependent transport critical current as a function of applied field for these films, as well as microstructural measurements by transmission electron microscopy are also reported. The angular and field dependence of critical current density are similar to standard PLD (pulsed laser deposition) films. Although the films are of high epitaxial quality they contain yttria precipitates which are possible sources of flux pinning centers. Index Terms—Coated conductors, HLPE, hybrid liquid phase epitaxy, thick YBCO films, YBCO growth rate.

S. R. Foltyn

Papers

Superconductor GdBa2Cu3O7−δ edge junctions with lattice‐matched Y0.6Pr0.4Ba2Cu3O7−δ barriers

Thermal regrowth of ion-damaged YBa2Cu3O7−δ superconducting thin films

Dual Ion Assist Beam Deposition of Magnesium Oxide for Coated Conductors

Improving flux pinning in YBa[sub 2]Cu[sub 3]O[sub 7] coated conductors by changing the buffer layer deposition conditions

Coated Conductor Grown by Hybrid Liquid Phase Epitaxy