Electrical switching of some zinc oxide based ceramics

Electrical switching of some polycrystalline ZnO based ceramics was investigated. The electrical characteristics of multicomponent, two-phase, and single-phase materials were related to the microstructures and defect structures of those materials;Subsequent to the study of the multiphase microstructure of multicomponent switching materials, a simplified two-phase threshold switching material was produced consisting of Co-doped ZnO and Zn-doped PrCoO(,3) phases. The roles of individual grains and interphase boundaries in the switching behavior of the two-phase threshold switching material were identified using microelectrodes deposited photolithographically on a thin section of the material. Pristine Co-doped ZnO grains showed high \u27off\u27 state resistance and a high \u27threshold\u27 voltage drop for the initial voltage sweep and were permanently conductive for subsequent sweeps. Zn-doped PrCoO(,3) grains exhibited stable and reproducible threshold switching behavior. Through the study of the electrical characteristics of single-phase polycrystalline undoped and Co-doped ZnO materials and undoped and Zn-doped PrCoO(,3) materials, the microelectrode observations of the switching behavior of the two-phase material were confirmed. Undoped ZnO showed n-type conductivity with resistivity of around 1 (OMEGA)-cm. Doping ZnO with Co increased the resistivity. It was established through a series of studies that the resistivity increase in ZnO accompanying doping with Co was not due to blocking contacts. A model was proposed for this resistivity increase. Undoped and Zn-doped PrCoO(,3) showed p-type conductivity with a resistivity of around 100 (OMEGA)-cm. Doping PrCoO(,3) with Zn decreased the resistivity. A blocking contact was observed between PrCoO(,3) and electrode metals having low work functions;The Hunter model for switching behavior of ZnO-based materials was tested on the basis of the observed microstructure in the two-phase material, and was found not to be appropriate. A microscopic model of the switching behavior of the two-phase materials was proposed

Evaluation of the Role of Hydroxyapatite in TiO2/ Hydroxyapatite Photocatalytic Materials

The TiO2/hydroxyapatite (HAp) composite has attracted much attention as a photocatalyst for pollution treatment in water or air because this composite can improve the properties of pure TiO2 including a low efficiency, narrow light response range, low adsorption capacity for hydrophobic contaminants, and difficult recovery of TiO2 particles after using in Aquarius environment. To obtain the best composite containing the two components including TiO2 and HAp, the role of HAp in TiO2/hydroxyapatite photocatalytic material should be analyzed and evaluated. This chapter will significantly present a review of the role of HAp in the TiO2/hydroxyapatite composite including the adsorption ability of contaminations and the promoted impacts of HAp component

Effect of Ag nanoparticle concentration on the electrical and ferroelectric properties of Ag/P(VDF-TrFE) composite films

We investigated the effect of the Ag nanoparticles on the ferroelectric and piezoelectric properties of Ag/poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) composite films. We found that the remanent polarization and direct piezoelectric coefficient increased up to 12.14 μC/cm^2 and 20.23 pC/N when the Ag concentration increased up to 0.005 volume percent (v%) and decreased down to 9.38 μC/cm^2 and 13.45 pC/N when it increased up to 0.01 v%. Further increase in Ag concentration resulted in precipitation of Ag phase and significant leakage current that hindered any meaningful measurement of the ferroelectric and piezoelectric properties. 46% increase of the remanent polarization value and 27% increase of the direct piezoelectric coefficient were observed in the film with the 0.005 v% of the Ag nanoparticles added without significant changes to the crystalline structure confirmed by both X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) experiments. These enhancements of both the ferroelectric and piezoelectric properties are attributed to the increase in the effective electric field induced by the reduction in the effective volume of P(VDF-TrFE) that results in more aligned dipoles

Electrical switching of some zinc oxide based ceramics

Electrical switching of some polycrystalline ZnO based ceramics was investigated. The electrical characteristics of multicomponent, two-phase, and single-phase materials were related to the microstructures and defect structures of those materials;Subsequent to the study of the multiphase microstructure of multicomponent switching materials, a simplified two-phase threshold switching material was produced consisting of Co-doped ZnO and Zn-doped PrCoO(,3) phases. The roles of individual grains and interphase boundaries in the switching behavior of the two-phase threshold switching material were identified using microelectrodes deposited photolithographically on a thin section of the material. Pristine Co-doped ZnO grains showed high 'off' state resistance and a high 'threshold' voltage drop for the initial voltage sweep and were permanently conductive for subsequent sweeps. Zn-doped PrCoO(,3) grains exhibited stable and reproducible threshold switching behavior. Through the study of the electrical characteristics of single-phase polycrystalline undoped and Co-doped ZnO materials and undoped and Zn-doped PrCoO(,3) materials, the microelectrode observations of the switching behavior of the two-phase material were confirmed. Undoped ZnO showed n-type conductivity with resistivity of around 1 (OMEGA)-cm. Doping ZnO with Co increased the resistivity. It was established through a series of studies that the resistivity increase in ZnO accompanying doping with Co was not due to blocking contacts. A model was proposed for this resistivity increase. Undoped and Zn-doped PrCoO(,3) showed p-type conductivity with a resistivity of around 100 (OMEGA)-cm. Doping PrCoO(,3) with Zn decreased the resistivity. A blocking contact was observed between PrCoO(,3) and electrode metals having low work functions;The Hunter model for switching behavior of ZnO-based materials was tested on the basis of the observed microstructure in the two-phase material, and was found not to be appropriate. A microscopic model of the switching behavior of the two-phase materials was proposed.</p

Visualization and manipulation of meta-stable polarization variants in multiferroic materials

Here we demonstrate the role of meta-stable polarization variants in out-of-plane polarization switching behavior in epitaxially grown BiFeO3 thin films using angle-resolved piezoresponse force microscopy (AR-PFM). The out-of-plane polarization switching mainly occurred at the boundary between meta-stable and stable polarization domains, and was accompanied by a significant change in in-plane domain configuration from complicated structure with 12 polarization variants to simple stripe structure with 4 polarization variants. These results imply that the biased tip rearranges the delicately balanced domain configuration, which is determined by the competition between electrostatic and strain energies, into simple interweaving one that is more thermodynamically stable

Conducting Polymer PEDOT:PSS: An Emerging Material for Flexible and Transparent Electronics

A one dimensional variable range hopping type conduction is observed in Poly (3, 4- ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS) films obtained by a spin coating technique on polyethylene naphthalate (PEN) substrate and the mechanism behind enhancement in conductivity in 3 % dimethyle sulfoxide (DMSO) doped PEDOT:PSS film is due to the phase segregation of PSS on the surface and reduction of energy barrier between the conducting grains. Enhanced conductivity of PEDOT:PSS films and transparency more than 80 % in the visible region makes PEDOT:PSS films suitable for flexible and transparent optoelectronic devices

Room temperature multiferroic properties of single-phase (Bi₀.₉La₀.₁)FeO₃-Ba(Fe₀.₅Nb₀.₅)O₃ solid solution ceramics

The crystal structure and multiferroic properties of single-phase (Bi₀.₉La₀.₁)FeO₃–Ba(Fe₀.₅Nb₀.₅)O₃ ceramics were investigated. The rhombohedral-type structure of 1.0(Bi₀.₉La₀.₁)FeO₃) was transformed to a monoclinic-type structure for the 0.5(Bi₀.₉La₀.₁)FeO₃–0.5Ba(Fe₀.₅Nb₀.₅)O₃) composition. It shows the coexistence of ferroelectricity and magnetism at room temperature, represented by a high dielectric constant with ferroelectric hysteresis and clear magnetic hysteresis behavior. The authors propose that the solid solution of A and B site cations according to their ionic radii and valence state stabilized the spontaneous polarization and magnetization at room temperature.Keywords: valency, bismuth compounds, dielectric polarisation, permittivity, ferromagnetic materials, magnetic hysteresis, ferroelectricity, ferroelectric ceramics, multiferroics, barium compounds, crystal structure, lanthanum compounds, dielectric hysteresi