1. The nominal composition (in batch) The provisions of the oxygen atoms
209
Electrical and structural characteristics of the composites based on amorphous-crystalline polymer ferroelectrics and ferrite powders
Introduction
Composite materials (CM) are widely used in mechanical engineering, building, optics. Composites are of particular interest for electronics, microsystems technology and radio-technical application. Composites often have unique properties which are different from the characteristics of the constituent elements.
Nowadays active studying of CM is important issue. Due to the magnetic and dielectric properties of ferrites, much attention has been payed to polymer-based composites filled with ferrites, for their applications in various areas such as information storage, electromagnetic wave absorption, bio-separation, and diagnostics. Their magnetostrictive properties also make them good candidates for magnetoelectric composites [1, 2]. Beside this, those materials are easy to process, what allows them to be used in production of complex shape wares. Strong dependence of CMs’ characteristics based on ferrites powders in dielectric matrix on phase dispersion of the filler is typical for magnetodielectric composites. Previously, the phenomenon of effective permittivity enhancement was observed in ferrite-dielectric composites, where volume concentration of granulated ferrite powder exceeded a certain amount (fig. 1.a) [3].
Development of CM based on ferroelectrics, which properties could be controlled by external electrical field, seems a promising issue (fig. 1.b).
Table 1 – Crystallographic parameters of ferrite powders
Z.V. Mingazheva, R.I. Shakirzyanov, V.A. Astakhov, 
A.T. Morchenko, V.V. Kochervinskii, L.V. Panina,
N.A. Shmakova, V.G.Andreev, S.A. Bedin,
V.V. Korovushkin, B.K. Argymbek, S.V. Miroshin
National University of Science and Technology, MISiS
119991, Moscow, Russia, Leninskiy prospekt, 4
*AA.T. Morchenko:
Ferrite Brand
The nominal composition (in batch)
Fraction (microns)
Parameter of cell
The provisions of the oxygen atoms
a, Å X
2000NM
Mn0.5792Zn0.2597Fe0.1612Fe2O4
<45
8.4688(2)
0.259(2)
80‑200
8.4685(3)
0.259(3)
200‑315
8.4328(2)
315‑500
8.4698(3)
500‑1000
8.4709(3)
Electro-physical properties of SKF32 and F42
Studying the samples which were fabricated by melt crystallization under pressure method was performed with the help of the immittance RLC-meter. 6
Figure 6 – Micrograph of granulated Mn-Zn ferrite powder
Ferrite-ferroelectric CM
It was considered that ferrite particles may be centers of β-phase crystallization, filling place between polymers crystals (Fig. 7). The dependence of the specific heat of crystallization on the bulk filler concentration was investigated from the analysis of differential scanning calorimetry data for F42 based composites (Fig.8).
Permittivity spectra was investigated for F42/Mn-Zn ferrite in a range of frequency 25 Hz – 1 MHz (fig.9).
Figure 8 – Dependence of specific heat on volume concentration of filler in F42/Mn-Zn ferrite composite
Figure 9 – Permittivity spectra for F42/Mn-Zn ferrite composite,
a – initial component of matrix (F42), b – composite with 5% of volume filler concentration, c – 10 %, d – 30 %, e – spectra of Mn-Zn ferrite 7 a) b)
Figure 3 – Dependence of dielectric loss tangent (a), and the conductivity (b) on frequency for SKF-32 and F-42 3
On Properties of Magneto-dielectric Composites in the Effective Medium Approximation/A.T. Morchenko et al // Journal of Nano- and Electronic Physics, 2014, Vol. 6, No 3, P ).
Structural properties of SKF32 and F42
Structural properties of polymers were investigated by using differential scanning calorimetry and infrared spectroscopy methods. Thermograms of SKF32 and F42 show the absence of the characteristic peak of heat absorption in the SKF32, which indicates the absence of a phase transition (Fig.4). The infrared spectrum of SKF32 indicates a decrease in the peak intensity 840 cm-1, which is responsible for the presence of crystalline phase (Fig.5). a)
Eext
P, M, ε, µ,
tg δε, tg δµ
Figure 7 – Schematic representation of the filler particles arrangement in the matrix b)
Figure 1 – Illustration of CMs’ characteristics dependence on filler’s concentration (a), and on external electrical field (b) 1
Ferroelectric polymers as a matrix for CM
Polyvinylidinefluoride (PVDF) is crystallizable polymer with high pyroelectric and piezoelectric properties. Along with this, PVDF has a high elasticity, transparent and easy to manufacture, which makes this polymer suitable for a wide range of technological applications [4].
F42, SKF32 are PVDF copolymers with high strength, chemical and radiation resistance, weather and fire resistance.
Figure 4 – Results of differential scanning calorimetry for SKF32, F42 4
Figure 5 – Infrared spectra for SKF32, F42 a)
Mn-Zn ferrite as a filler in CM
Mn-Zn ferrite (brand 2000NM) is soft magnetic spinel ferrite used in electronics. Parameters: magnetic permeability µa = 2000 ± 300, µmax=3500, magnetic losses tgδ/µн = 15∙106 at H=0.8 A/m and f=0.1 MHz, electrical resistance ρ = 0.5 Ohm∙m, residual induction Br=0.13 Т, coercive force Hc=24 A/m, TC= 200 oС, density p = 5 g/cm3.
The porosity and density of used granulated powders was about and g/cm3, respectively. b)
Figure 2 – Chemical structural formula SKF32 (a) and F42 (b) 2 5
Conclusions
Composite materials «polymer F42 / Mn-Zn ferrite», «polymer SKF32 / Mn-Zn ferrite» were produced by using polymer crystallization from solution method.
The properties of the constituent elements of the composite SKF32, F4/Mn-Zn ferrite were investigated.
It was found, that samples of SKF32, which were produced by solidification from melt, as well as from solution, are amorphous, while F42 samples have crystal structure and exhibit piezoelectric effect.
Evaluation of the effect of the ferrite particles onthe polymer matrix was investigated; it is shown, that the fillers promote the formation of new crystallization nuclei in the polymer F42.
The dependence of the electrical properties of the composites on filler concentration was investigated. It is shown, that in composites which were produced by crystallization of the polymer F42 from solution the dielectric constant of the composite rises with increasing the ferrite phase.
References
1. Dielectric and magnetic properties of ferrite/poly (vinylidene fluoride) nanocomposites/P. Martins, C.M. Costa, G. Botelho, S. Lanceros-Mendez, J.M. Barandiaran, J. Gutierrez // Materials Chemistry and Physics – – Vol.131, Is. 3, – P. 698–705.
2. Linear anhysteretic direct magnetoelectric effect in Ni0.5Zn0.5Fe2O4/poly(vinylidene fluoride-trifluoroethylene) 0-3 nanocomposites/ P Martins, X Moya, L C Phillips, S. Kar-Narayan, N.D. Mathur and S. Lanceros-Mendez // J. Phys. D: Appl. Phys. – –V ol 44, – P. 1–4.
3. On Properties of Magneto-dielectric Composites in the Effective Medium Approximation/A.T. Morchenko, L.V. Panina, S.V. Podgornaya, V.G. Kostishyn, P.A. Ryapolov //Journal of Nano- and Electronic Physics – – Vol. 6 No 3, – P (6pp).
4. V.V.Kochervinskii -The structure and properties of block poly(vinylidene fluoride) and systems based on it// Russian Chemical Reviews – – Vol.65 (10). – P