0000000000364612
AUTHOR
Gundars Mezinskis
Gas sensing properties of Zn-doped p-type nickel ferrite
Abstract The influence of zinc ion to the NiFe2O4 p-type semiconductor gas response characteristics is demonstrated. For characterization of gas sensor material, synthesized by sol–gel auto combustion method, X-ray diffraction (XRD), scanning electron microscopy (SEM), DC resistance and impedance spectroscopy (IS) measurements were employed. The response change of Zn doped nickel ferrite is related to the interruption of hole hopping between nickel ions. This was improved by change of conductivity type with temperature and gas exposure.
Properties of Ni–Zn ferrite thin films deposited using spray pyrolysis
Abstract Nanocrystalline, homogeneous spinel Ni 1 − x Zn x Fe 2 O 4 thin films were deposited on glass substrates by using spray pyrolysis of metal nitrate aqueous solutions. The thickness of deposited films was below 500 nm, but crystallite size was under 30 nm. It has been shown that the DC resistivity, dielectric loss and optical band gap of deposited films are influenced by the zinc content. High DC resistivity and low dielectric losses of thin Ni 1 − x Zn x Fe 2 O 4 films are explained by mixed n-p conductivity and nanograin structure of spray pyrolysis deposited coatings which are changing with the ratio of Ni/Zn.
Effect of antisite defects on the magnetic properties of ZnFe2 O4
Magnetic zinc ferrite (ZnFe2O4) nanopowders were synthesized using the sol–gel autocombustion method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements demonstrated that thermal decomposition of the 1-mm-thick xerogel layers in air formed monophasic spinel ferrite nanopowders with a particle size less than 30 nm. X-ray photoelectron spectroscopy (XPS) showed that the obtained reaction product contained antisite defects, with zinc ions occurring at the octahedral sites of the spinel structure. The concentration of antisite defects or inversion degree decreased when the relatively low annealing temperature was increased from 150 to 500 °C. Overall, the obtained ZnFe2…
Electric and dielectric properties of nanostructured stoichiometric and excess-iron Ni–Zn ferrites
In this paper, we report a study of the effect of excess iron on structural, microstructural, electric and dielectric properties of the nanostructured Ni–Zn ferrites Ni1−xZnxFe2+zO4−δ of different compositions with x = 0, 0.3, 0.5, 0.7, 1 and z = 0, 0.1. The structural and microstructural properties are estimated from x-ray diffraction and atomic force microscopy (AFM) data. The average grain size, evaluated from AFM topographical analysis, is found to be below 70 nm. The samples exhibit low values of dielectric constant and dielectric loss and a high resistivity. Contrary to earlier conclusions regarding microstructured Ni–Zn ferrites, in nanostructured Ni–Zn ferrites sintered at relativel…
Preparation and Characterization of Nanostructured Fe-TiO2 Thin Films Produced by Electrophoretic Deposition
Fe-TiO2 thin films have been produced by a sol-electrophoretic deposition method on metallic Ti foil substrates. X-ray diffractograms and Raman spectra confirms the anatase structure of deposited and annealed Fe-TiO2 films. Obtained Fe-TiO2 thin films demonstrate photoactivity under visible light radiation due to the doping with Fe3+ ions. Open circuit potential results shows that increase of the film thickness and surface area improves the photoactivity of Fe-TiO2.
Immobilisation of yeast cells on the surface of hydroxyapatite ceramics
Hydroxyapatite (HAP) ceramics was tested for the first time for the possibility of being used as a new carrier for the immobilisation of yeast cells that are both model organisms for eukaryotic cell investigations and producers, which is important in classical and modern biotechnological processes. It was shown that under typical immobilisation conditions yeast (Saccharomyces cerevisiae) has no affinity to HAP ceramics. A novel method for yeast immobilisation was developed. This new method includes the joint incubation of a carrier with the cells, the sedimentation and adhesion of cells on the carrier and the dehydration of obtained preparations. It was shown that the sedimentation and adhe…
Influence of iron non-stoichiometry on spinel zinc ferrite gas sensing properties
Abstract It is demonstrated for the first time that the gas sensing properties of a spinel ferrite complex metal oxide semiconductor can be improved by controlling iron stoichiometry. Conductivity and sensitivity was analyzed for ZnFe2+zO4± spinel type ferrite with z from −0.01 to 0.15. By increasing iron content from z = −0.01 to z = 0.1, sensitivity increases up to 3 times but for samples with z > 0.1 sensitivity drops. It was observed from impedance spectroscopy measurements that resistance decreases with an increase of the iron content. Complex impedance spectra reveal two phases with different resistance attributed to depletion layer (Rd) and bulk (Rb). With increasing iron content inc…
CO2 laser-induced structure changes in lead zirconate titanate Pb(Zr0.58Ti0.42)O3 sol–gel films
Based on absorption spectra of lanthanum modified lead zirconate titanate Pb0.9La0.1(Zr0.65Ti0.35)O3 (PLZT10/65/35) ferroelectric ceramics an idea of local and selective treatment of lead zirconite titanate Pb(ZrXTi1−X)O3 (PZT) sol–gel film in the multi-layer structure by CO2 laser radiation was formulated. The possibility to obtain PZT perovskite film on the SiO2/Si substrate by irradiation with CO2 laser was shown experimentally. X-ray studies revealed the PZT perovskite structure ratio growth at the expenses of pirochlore structure with an increased power density of laser radiation.