Structural, optical and electrical properties of multiferroic BiFe1-xNixO3 ceramic
- 200 Downloads
BiFe1−xNixO3 (x = 0.7, 0.8 and 0.9) polycrystalline ceramics are synthesized by a solid-state reaction, and their structural, absorption, leakage current and electrical properties are investigated. The X-ray diffraction measurements show that the lattice parameter values increase with increasing the substitution of Ni2+ ions for Fe3+ ions. The optical absorption spectra indicate that the band gap energy increases with increasing Ni2+ ions. Leakage currents are much decreased by about three orders of magnitude with increasing Ni ions. The J-E hysteresis was also investigated. Both real and imaginary dielectric constants are investigated as a function of both frequency and temperature. The room temperature dielectric measurement with a wide frequency range of 1 KHz–1 MHz reveals that the real and imaginary dielectric constants are decreased with increasing frequency of BiFe1−xNixO3 (x = 0.7, 0.8, 0.9) ceramics. The real and imaginary dielectric constants are found to be increased with temperature. The temperature dependence of ε′ and ε″ exhibits an anomaly which shifted to lower temperature with increasing Ni2+. The anomaly indicates the possible existence of spin-glass states with Ni2+ ion substitution in places of Fe3+ ions.
KeywordsPerovskite-like type structure X-ray diffraction Absorption spectra Leakage current Spin-glass state
In multiferroic system, a coupling of at least two or all three of antiferroelectricity, antiferromagnetism and ferroelectricity characteristic are observed in the same phase [1, 2, 3]. The existence of both ferroelectric, ferromagnetism and elasticity in such a system will provide more degree of freedom in the field of new functional sensors and actuators [1, 4, 5]. BiFeO3 represents one of such set of perovskite multiferroics family which has a ferroelectricity phase with cure temperature (Tc) that is around 820–850 °C [6, 7] and has an antiferromagnetic transition (TN) around 370–380 °C [6, 8]. The leakage current represents the main problem for such material, this is due to its low resistivity which is reflected as its instability . The co-existence of both vacancies and Fe2+ ions represents the main source of leakage current [10, 11, 12, 13, 14]. Several attempts were carried out to overcome such problems using doping techniques. This was done by substituting part of Bi+3 with dope ions at the side A of BiFeO3 ceramic structure [15, 16, 17, 18] or with substituting another type of dope ions (Nb+5, Mn+4, Ti+4 or Cr+3) at site B (Fe3+) [19, 20, 21]. The doping process leads to an improvement of ferroelectric properties and a reduction of the leakage current of BiFeO3 ceramic to some extent.
As a photocatalytic material, BiFeO3 had been examined in a visible region of light. Its photocatalytic degradation returns to its narrow optical band gap (~ 2.2 eV) and its chemical stability [22, 23].
In this work, we report the synthesis of BiFe1−xNixO3 ceramic with a composition of x = 0.7, 0.8 and 0.9 and study the influence of aliovalent ions of Ni2+ substitution, on structural, optical absorption, leakage current and dielectric behaviour of BiFe1−xNixO3 ceramic. The doping with Ni2+ may prevent the formation of Fe2+ and then reduce the oxygen vacancies which cause an improvement of the electrical properties of such multiferroic ceramic. The reduction of oxygen vacancies after the Ni2+ doping process which will prevent Fe2+ formation was expected.
By using the solid-state reaction, BiFe1−xNixO3 (x = 0.7, 0.8 and 0.9) were synthesized from highly pure Bi2O3, (1 − x) Fe2O3 and 2xNiO powders. The weighed powders were milled mixed for half an hour at room temperature in air atmosphere. This milled powder was pressed into 16 mm diameter and 1 mm thickness discs under 1.5 Mpa pressure on a hydraulic press and then were rapidly heated to 750 °C and sintered for 30 min at atmospheric pressure. The calcined powder was milled again for half an hour. Then, they were pressed again into pellets of 16 mm diameter by applying a pressure of 1.5 Mpa. The pellets of the sample were found to be dark grey upon Ni substitution. For measurements of electrical properties, the ceramic pellets were coated on both surfaces with silver paint for good contacts.
The structure of the samples is characterized by X-ray diffractometer (X’Pert-Pro MPD, Philips) using CuKα radiation with λ = 1.541874 Å. The patterns were recorded in a 2θ interval of 20–60 with increments of 0.025 (2θ). The photo-absorption of BiFe1−xNixO3 was measured by UV-visible diffuse reflectance spectrophotometer ShimadzuUV-3600. The electric properties were measured using the semiconductor characterization system SCS4200 (Keithly). The electric data were carried out as a function of temperature and frequency during heating of the samples from room temperature up to 280 °C and frequency range from 5 kHz to 5 MHz.
Result and discussion
where R∞ = Rsample/Rpref.
K is a constant, and n is the exponent which depends on the type of transition .
The electrical hysteresis (IV loop) for sample x = 0.9 is represented in Fig. 5c. It is clearly noted that the area of the hysteresis decreases with decreasing Ni content, the symmetry of the curve behaviour (− 20 ➔ 0 ➔ + 20) increase with decreasing Ni content, and the shift between the two minima (m1 and m2 in Fig. 5c of the cycle becomes close to each other with decreasing Ni content. This behaviour can be attributed to the existence of trapping and detrapping process beside the cle bipolar resistive element which decreases the effect of the space charge carrier.
The high nickel dopant induced changes in the structure, optical absorption and leakage current; the J-E hysteresis and dielectric properties of BiFe1−xNixO3 samples have been investigated. It is shown that the BiFe1−xNixO3 crystallizes in the triclinic crystal structure. The cell parameters increase with increasing x doping, and optical band gaps decrease with increasing x. Leakage current were much reduced with Ni+2 ion doping, it was decreased by about three orders of magnitude. The area of the hysteresis decreases with decreasing Ni doping. It is also found that the doping of Ni+2 ions can effectively reduce the leakage current density and improve the ferroelectric properties. The dielectric constants ε′ and ε″ were found to be decreased with increased frequency. The real ε′ and imaginary ε″ dielectric constants were found to be increased with temperature. The temperature dependence of ε′ and ε″ exhibited an anomaly which shifted to lower temperature with increasing Ni+2 ion doping. The anomaly indicates the possible existence of spin-glass states with Ni2+ ion substitution in the place of Fe3+ ions.
The authors would like to express their deep gratitude to King Faisal University, College of Science–Physics Department and the Deanship of Scientific Research for their kind supports. This study was supported by the Deanship of a Scientific Research (King Faisal University): proposed no. 186036.
- 2.S. Kumari, D.K. Pradhan, R.S. Katiyar, A. Kumar,: Elsevier, , p. 571 (2018)Google Scholar
- 3.N.I. Ilic, B.D. Stojanovic: Elsevier, p. 527, (2018)Google Scholar
- 4.C.E. Ciomaga, L. Mitoseriu,: Elsevier, p. s,( 2018)Google Scholar
- 6.Roginskaya, Y.E., Tomashpol’Skii, Y.Y., Venevtsev, Y.N., Petrov, V., Zhdanov, G.: Soviet. J. Exp. Theor. Phys. 23(47), (1966)Google Scholar
- 7.Kubel, F., Schmid, H.: Structural Science. 46, 698–702 (1990)Google Scholar
- 8.Kiselev, S., Ozerov, R.P., Zhudanov, G.S.: Detection of magnetic order in ferroelectric BiFeO3 by neutron diffraction. Sov Phys. 7, 742 (1963)Google Scholar
- 12.Sarkar, T., Elizabeth, S., Kumar, P.A.: J. Magn. Magn. Mater. 448(266), (2018)Google Scholar
- 15.Yu, B., Li, M., Liu, J., Guo, D., Pei, L., Zhao, X.: J. Phys. D. Appl. Phys. 41(065003), (2008)Google Scholar
- 25.Betancourt-Cantera, L.G. ; Bolarín-Miró, A.M., Cortés-Escobedo C.A.;, Hernández-Cruz, L.E.;Sánchez-De Jesús, F.; J. Magn. Magn. Mater., 456, 381( 2018)Google Scholar
- 28.Kortüm, G.: Reflectance spectroscopy: principles, methods, applications. Springer Science & Business Media (2012)Google Scholar
- 35.Arafat, S., Ibrahim, S.: Mater. Sci. Appl. 8, 716 (2017)Google Scholar
- 39.Karim, S., Reaney, I.M., Levin, I., Sterianous, I.: Appl. Phys. Lett. 94(112903), (2009)Google Scholar
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.