Oleksandr Boiko

Capacitive properties of nanocomposite (FeCoZr)x(PZT)(100-x) produced by sputtering with the use of argon and oxygen ions beam

The paper established that, the hopping mechanism of the charge exchange for the (FeCoZr)64.4(PZT)35.6 nanocomposite and the additional polarization of tested sample occurs. As frequency increases two frequency areas where capacitance decreases can be observed. Correlation between the conductivity increase and the capacitance decrease has been observed for the both stages of their variability. Voltage resonance phenomenon for the studied material was observed. The zero crossing in the frequency dependence of phase difference transition is accompanied with this phenomenon, which is reflected by a sharp minimum in the capacitance versus frequency characteristics.

Voltage resonance phenomenon and simulation of electrical properties of (FeCoZr)x(PbZrTiO3)(100-x) nanocomposite films

In this paper, the frequency dependencies of phase angle, capacity in a parallel replacement system, conductivity and loss coefficient of ferromagnetic alloy – ferroelectric ceramics nanocomposite (FeCoZr)x(PbZrTiO3)(100-x) with x = 55.9 at.% were studied. Tested material was deposited by ion beam sputtering with use of mixed argon-oxygen atmosphere in a vacuum chamber and subdued by a 15-min annealing in air in the temperature of Ta =498 K. The type of electrical conduction in the material for frequencies f < 2×105Hz was defined as capacitive. At frequencies above fR = 2×105 Hz there are positive phase angle values, which corresponds to the inductive type of conduction. This means that the voltage resonance occurs in the nanocomposite, which indicates the voltage compensation on the reactive (inductive and capacitive) components of the impedance in the sample. It leads to the appearance of minima and maxima on the Cp(f) and tgδ(f) characteristics respectively. The σ(f) characteristic demonstrates strong conductivity dependence from frequency, which can be explained by hopping mechanism of charge exchange in the material. The simulation of AC electrical parameters based on parallel connection of two branches with serial RLC elements were performed for the frequency range 50 Hz < f < 106Hz. It demonstrates high compatibility of measured and calculated results which suggests the possibility of replacing the actual conventional RLC circuits of electronic components and finding other applications of (FeCoZr)x(PbZrTiO3)(100-x) nanocomposites in electronics and engineering.

Low temperature electrical conductance in (FeCoZr)x(PbZrTiO3)(100-x) nanocomposite films

In this paper, the temperature and frequency dependences of conductivity, capacity and phase angle of two nanocomposite samples containing Fe0.45Co0.45Zr0.10 – based nanoparticles embedded in a doped PbZrTiO3 ferroelectric matrix were studied. AC measurements have been performed for the low temperatures (15 K ≤ TP) and within frequency range 50 Hz – 1 MHz. The nanocomposites studied were deposited by ion beam sputtering with use of different synthesis atmosphere in a vacuum chamber. The samples were subdued by a 15-min annealing in air in the temperatures of TA1 = 698 K and TA2 = 623 K. It was found that for the nanocomposite sample produced using low oxygen content in the synthesis atmosphere (x1 = 57.6 at.%) negative values of phase angle θ occur, which indicates capacitive type of conduction in the material. We can also notice the strong rapid frequency and temperature dependences of conductivity for this sample. It can be related with hopping carrier transport in the nanocomposite. For the nanocomposite sample with x2 = 57.6 at.%, which was produced using high oxygen content in the synthesis atmosphere we can observe occurrence of positive values of θ for frequencies f > 5×104 Hz. It can be related with the additional oxidation of Fe0.45Co0.45Zr0.10 nanoparticles during the annealing process (potential barriers surround nanoparticles). The type of carrier transport in the nanocomposite samples is defined as hopping.

Structural features of the multilayer nitride coatings formation

The features of structure and properties formation of multicomponent (high-entropy) and multilayer transition metals nitride coatings of deposited by reactive magnetron (HF and DC) sputtering of targets in Ar + N2 mixture atmosphere was analyzed. It is shown that the formation of texture and columnar structure of films occurs due to changes the deposition conditions. Moreover, transition metals nitride films (TiN, HfN, et al.) have textured growth plane (111) and nanohardness values about 36 GPa at close to stoichiometric compositions. X-ray analysis of nitride multilayer coatings shows that the multilayers have a cubic structure with a preferential orientation (111) or (200) depending on the period of modulation Λ. It is shown that one of the methods of its preparation is the use of elements (Zr,Y). Correlations between structure and physico-mechanical properties of the coatings, as well as the effect of multilayers deposition conditions and modulation period on the hardness value were exhibited. Conducted researches show that the use of multi-component and multi-layered nitride coating allows to obtain super hard nitride coating (> 40 GPa,) with high elastic recovery (We up to 83%) and high resistance to plastic deformation (H3/E*2 up to 0.75).

Impedance of (CoFeZr)0,559(PbZrTiO3)0,441 nanocomposite annealed in a tubular furnace

The objective of the present research has been to determine the influence of annealing in tubular furnace on capacity of (CoFeZr)0,559(PbZrTiO3)0,441 nanocomposite produced by ion beam sputtering using combined argon and oxygen beam. The phase angle of the nanocomposite directly after preparing demonstrates negative values, which indicates the capacitive type of electrical conductivity of the material. The rapid increase of conductivity when frequency increases indicates hopping conductance in the material. The additional polarization of the nanocomposite occurs with its extinction in the area of high frequencies. The electrons relaxation time has been defined as of ca τ = 1,25×10-4 s. Annealing of nanocomposite sample x = 55.9 at.% at temperature Ta = 548 K causes phase angle obtains positive values in high frequency area, which indicates the change of conduction type from capacitive to inductive. The voltage resonance phenomenon occurs in the material. Annealing in temperature of Ta = 648 K causes changes of the nanomaterials capacity. The additional oxidization of CoFeZr metallic phase nanograins which provides to the potential barrier formation around potential wells (CoFeZr nanoparticles).

AC conductivity of (FeCoZr) x (PZT) (100-x) nanocomposites produced in vacuum chamber

In this work, the temperature and frequency dependences of conductivity σ and Arrhenius plots of annealed nanocomposite films containing Fe45Co45Zr10 - based nanoparticles embedded in a doped PbZrTiO3 ferroelectric matrix were studied. The nanocomposites studied were deposited by sputtering with use of argon and oxygen ions in a vacuum chamber. Tested samples were followed by a 15-min annealing process in air in the temperature range of 398 K ≤ Ta ≤ 748 K with steps of 25 K. The σ(f,T) dependences of nanocomposite samples was measured in ambient temperature range of 77 K < Tp < 373 K at frequencies of 50 Hz < f < 1MHz. It was established that nanocomposite sample with metallic phase content x = 55.6 at.% demonstrates strong temperature and frequency dependences, which is typical for a percolation systems. Type of conduction in such nanostructure is defined as dielectric, which may be related with the additional oxidation of metallic nanoparticles during the annealing process. For the tested sample with x = 88.4 at.%. we observe metallic type of conduction, when metallic nanoparticles form a permanent conductive channels in dielectric matrix.