TITLE:
Correlations of Structural, Dielectric, Magnetic and Magnetoelectric Properties of Ca1-xSrx(Fe0.5Ta0.5)O3 Multiferroic Ceramics
AUTHORS:
M. K. H. Bhuiyan, M. A. Gafur, M. N. I. Khan, A. A. Momin, A. K. M. Akther Hossain
KEYWORDS:
Perovskite, Impedance Spectroscopy, Initial Permeability, Saturation Magnetization, Magnetoelectric Voltage Coefficient
JOURNAL NAME:
Materials Sciences and Applications,
Vol.8 No.1,
January
11,
2017
ABSTRACT: Conventional solid state
reaction technique was used to synthesize Ca1-xSrx(Fe0.5Ta0.5)O3 multiferroic ceramics (where x = 0.0,
0.1, 0.2, 0.3, 0.4 and 0.5). Powder of ingredients was mixed thoroughly in stoichiometric amount and calcined at 1150°C for 5
h. Disk and toroid shaped samples prepared from each composition were sintered
at 1450°C for 5 h. The XRD analysis confirms that all compositions are single
phase cubic perovskite structure. The theoretical and bulk density increases
with increase of Sr content, which may be attributed to the fact that the atomic weight and density of Sr are larger than those of Ca. The average grain
size increased with increasing Sr content up to x = 0.2, and then decreased with further increase of Sr content. Frequency dependent
dielectric constant shows usual dielectric dispersion at lower frequencies due
to Maxwell-Wagner type interfacial polarization. The higher values of real and
imaginary part of impedance at lower frequencies are also due to the fact that all kinds of polarization mechanism are present and increase with Sr content indicating the enhancement property
of the composition. The continuous dispersion on increasing frequency
contributes to the conduction phenomena. Two semicircles correspond to the
grain boundary and grain resistance separately. The complex modulus analysis
reveals the polaron hopping and negligibly small contribution of electrode
effect. The continuous dispersion on increasing frequency may be contributed to
the conduction phenomena. The ac conductivity, σac, was derived from the
dielectric measurement and it increases with increase of frequency for all the
compositions and can also be explained on the basis of polaron hopping mechanism. At
higher frequencies conductive grains are more active, and thereby increases of hopping of charge carrier contribute to rise in
conductivity. The real part of initial permeability increased with increasing
Sr content up to x = 0.2, and then decreased further increasing the Sr content. Firstly, it increased due to the higher values of grain size, and then decreased with the Sr content due to the lowering the grain size.
The saturation magnetization, Ms,
increases for x = 0.2 and then
decreases with increasing Sr content due to the pore acted as a pinning centre of electron spin; thereby Ms decreases also due to the grain size which is well supported by the permeability results. The decrease of
magnetoelectric voltage coefficient αME with content may be attributed to the increased porosity in the sample. The
presence of the pores breaks the magnetic contacts between the grains. The
highest value of αME is
42.22 mV·cm-1·Oe-1 for the composition x = 0.2 which is attributed to the
enhanced mechanical coupling. It was revealed that there is a dramatic
influence of Sr with content x = 0.2
and also has strong correlations on grain size as well as magnetic and
magnetoelectric properties.