Structural and Morphological Studies of Copper ...

Structural and Morphological Studies of Copper-Doped Nickel Ferrite

S. Mahalakshmi, K. Srinivasa Manja & S. Nithiyanantham

Journal of Superconductivity and Novel Magnetism Incorporating Novel Magnetism ISSN 1557-1939 J Supercond Nov Magn DOI 10.1007/s10948-015-3112-8

1 23

Your article is protected by copyright and all rights are held exclusively by Springer Science +Business Media New York. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com”.

1 23

Author's personal copy J Supercond Nov Magn DOI 10.1007/s10948-015-3112-8

ORIGINAL PAPER

Structural and Morphological Studies of Copper-Doped Nickel Ferrite S. Mahalakshmi1 · K. Srinivasa Manja2 · S. Nithiyanantham3

Received: 1 May 2015 / Accepted: 11 May 2015 © Springer Science+Business Media New York 2015

Abstract Ferrite nanocrystals are an interesting material due to their rich physical properties. Here we add non-magnetic dopant Cu to nickel ferrite nanocrystals, Ni1−x Mx Fe2 O4 (x = 0.2, 0.4, and 0.6) M = Cu, and study how relevant properties of the samples are modified accordingly. The grain size and the surface morphology were studied by scanning electron microscopy (SEM).Basically, these doping cause a rearrangement of Fe+3 ions into the two preexisting octahedral and tetrahedral sites. In fact, this, we show, induces pertinent magnetic properties of the doped samples. In the case of Cu doping, the Jahn–Teller effect also emerges, which we identify through the Fourier transform infrared spectroscopy of the samples. Moreover, we show an increase in the lattice parameters of the doped samples, as well a superparamagnetic behavior for the doped samples, while the Jahn–Teller effect precludes a similar behavior in the CuFe2 O4 nanocrystals. Keywords Nanoparticle · Nickel ferrite · SEM · XRD · FTIR · Structure · Morphology

S. Nithiyanantham

s [email protected] 1

Department of Physics and Nanotechnology, Faculty of Engineering and Technology, SRM University, Kattankulathur, Kanchipuram Dt., Tamil Nadu, 603203 India

2

Department of Physics, Pondicherry University, Pondicherry, 605014 India

3

School of Physical Sciences and Femtotechnology, (Magnetism and Magnetic Materials/Thin Film Division), SRM University, Kattankulathur, Kanchipuram Dt., Tamil Nadu, 603203 India

1 Introduction Copper ferrite is also an inverse spinel with tetragonal structure that shows a transition to cubic symmetry at high temperature. Copper ferrite is distinguished from other simple ferrites by an energy difference of about 0.1 eV between the normal and the inverse configuration [1]. Far infrared absorption spectroscopy has been used to study the occurrence of various absorption bands in the spectra and analyzed on the basis of different cations present on tetrahedral (A) and octahedral (B) sites of the spinel lattice [2–7]. Steirstadt et al. [8] reported that the fraction of Cu2+ ions occupying A sites can be changed from 0.11 to 0.18 by heat treatment. This results in a weakening of A–B exchange interaction and hence a decrease in curie temperature Tc . Nickel- and copper-substituted nickel ferrites are the important class of spinel ferrites [9]. Cux Ni1−x Fe2 O4 is known to exist in tetragonal and cubic structures. The temperature of the order–disorder transformation depends on the content of octahedral cupric ions and on the non-stoichiometry [10]. Its spinel lattice is highly distorted (c/a ∼ 1.06) because of the Cu2+ ion, as it is a Jahn–Teller (JT) ion arising from the octahedral cupric ions [11, 12] and also shows the inability to have a cation/oxygen ratio higher than 3:4. However, on the other hand, it was found to show anomalous favorable properties [1, 13] for different applications. Part of the Cu2+ ions can be frozen in tetrahedral sites when the ferrites were quenched in air from above 400 ◦ C [14]. The resulting ferrite material shows smaller tetragonal distortion since a great proportion of the cupric ions exist on tetrahedral sites. This sort of behavior is assumed to show impact on the position and valence of the ions in the crystal structure, and infrared spectra can give information about the position and valence of the ions in crystal lattices [15].

Author's personal copy J Supercond Nov Magn Fig. 1 X-ray diffractogram of Cu0.2 Ni0.8 Fe2 O4

Counts 800

cu2

600

400

200

0 20

30

40

50

60

70

Position [°2Theta]

Nanosized copper spinel ferrites show unusual properties in comparison with their bulk analogs and receive enormous attention during the last decade because of their potential applications. They can be obtained by a variety of methods such as solid-state reaction [16].

2 Experimental The samples having general chemical formula Cux Ni(1−x) Fe2 O4 , x = 0.2, 0.4, and 0.6, were prepared by taking copper rings, NiCl2 , and iron powder according to stoichiometric ratio. The copper rings, nickel chloride, and iron were weighed and dissolved in dilute nitric acid and then heated slowly to evaporate the solvent. The resulting black– brown precipitate is collected in a porcelain crucible and

Fig. 2 X-ray diffractogram of Cu0.4 Ni0.6 Fe2 O4

Counts

was kept in a furnace. It was kept in the furnace for 5 h at 50 ◦ C. Then it was allowed to cool slowly till it reaches the room temperature for nearly 1 h. The fired sample was ground thoroughly for an hour. It was kept in the furnace once again and heated to 85 ◦ C for 5 h. After cooling, it was again ground for 1 h to get a fine powder. The samples were tested for nanophase using XRD analysis. X-ray diffractogram was taken using X’Pert Pro with CuK-α radiation of wavelength 1.5418 A◦ . From X-ray diffraction analysis, completion of solid-state reaction and confirmation of single-phase formation were recorded. Scherrer’s formula was used for determining the particle size (t = 0.9λ / (β cos θ ), where t = particle size of the crystal, λ = wavelength of the CuK α radiation, β = full width at half maximum of the diffraction peak taken in radians, and θ = angle at which the maximum

C-4

1500

1000

500

0 20

30

40 Position [°2Theta]

50

60

70

Author's personal copy J Supercond Nov Magn

diffraction peak seen). A Fourier transform infrared spectroscopy (FTIR) transmittance spectrum for copper nickel ferrite is obtained using Shimadzu FTIR-8700 at room temperature 296 K.

3 Results and Discussion

Table 1 Variation of concentration of copper nickel ferrite with respect to lattice constant Concentration of copper nickel ferrite

˚ (m) Lattice constant A

Cu0.2 Ni0.8 Fe2 O4 Cu0.4 Ni0.6 Fe2 O4 Cu0.6 Ni0.4 Fe2 O4

8.3433 8.3551 8.3567

3.1 Structural Characterization Ferrites are commonly produced by conventional ceramic processes involving high-temperature (≥1200 ◦ C) solidstate reactions between the constituent oxides/carbonates. Non-conventional powder processing in a liquid medium may produce intermediate, finely divided mixed hydroxides or mixed organic salts to assist the subsequent diffusion process. There are two processing steps: powder preparation and sintering. The characteristics of the powder will strongly affect the quality of the product after sintering. Any remaining inadequacies in the powder can be corrected by extended times or higher temperatures in the sintering step, but usually at a cost of deterioration of other properties. The optimum combination is a coordinated process in which powder making and sintering enhance each other. The powdered samples of copper nickel ferrite showed the formation of single-phase cubic spinel structure showing well-defined reflections from allowed planes as shown in Figs. 1, 2, and 3. The variation of lattice constant was found to be increasing with the increase in the concentration of Ni. The variation of the lattice constant with the concentration of nickel is presented in Table 1. All Bragg reflections have been indexed, which confirm the formation of cubic spinel structure in single phase. The strongest reflection comes from the (311) plane, which denotes the spinel phase. The Fig. 3 X-ray diffractogram of Cu0.6 Ni0.4 Fe2 O4

peaks indexed to (111), (220), (311), (400), (511), and (440) planes of a cubic unit cell, and all planes are the allowed planes which indicates the formation of cubic spinel structure in single phase [17].The lattice constant is found to ˚ with increasing Cu content. increase from 8.343 to 8.356 A The lattice parameter values are in expected range with the lattice parameters of spinel cubic ferrites. This increase lattice constant can be attributed to larger ionic radiuses of ˚ relative to Ni2+ (0.69 A); ˚ this is consistent Cu2+ (0.72 A) with [18–21]. The lattice parameter increases more in Cu2+ substitution in the synthesized nanocrystals. The crystallite size was calculated for the all the compositions using the high-intensity 311 peak and using the Scherrer formula [22]. It is seen that the crystallite size is 24–36 nm. Where Dhkl is the crystalline size perpendicular to (hkl) plane, λ is the wave length of X-ray used, β is width of diffraction peak, i.e., full width at half maximum (FWHM), θ is the peak position. 3.2 FTIR Measurements Infrared spectroscopy was used to determine the local symmetry of the solids and to study the ordering phenomenon in the ferrites. IR absorption bands mainly appear due to the vibrations of the oxygen ions with cations at various

Counts C-6

1000

500

0 20

30

40 Position [°2Theta]

50

60

70


180 160

Transmittance

140 120 100 80 60 40 20

where ν = vibrational frequency of the ions, K = force constant of the ions, and M = effective mass of the ions.

100

100 80 60

40

40

20

20

400

500

600

700

800 -1

900

1000

1100

200

300

400

500

600

700

800 -1

Wavenumber(cm )

Wavenumber(cm )

Cu0.2Ni0.8Fe2O4

Cu0.6Ni0.4Fe2O4

Fig. 4 IR spectra of Cu0.2 Ni0.8 Fe2 O4

1000

ν = 1/2π K/m

120

300

800

and the ν2 band is due to vibrations of octahedral metal complexes. The Cu2+ ions occupy mainly the octahedral sites and some fraction goes into tetrahedral sites. Accordingly, this shoulder can be attributed to the vibration of Cu2+ –O2− in tetrahedral complexes. On the basis of the above discussion and on earlier studies [26], an inverted spinel structure can be assigned to the copper ferrite. By the qualitative analysis of the IR spectrum, the relation

120

200

600


140

60

400

-1

140

80

200

wavenumber(cm )

% Transmission

% Transmission

frequencies. An FTIR transmittance spectrum for copper nickel ferrite is obtained using Shimadzu FTIR-8700 at room temperature 296 K. IR absorption bands of the spectra are depicted in Figs. 4, 5, and 6. The spectra shows two main absorption bands ν1 and ν2 as common feature of all spinel compounds, in accordance with [23]. In copper nickel ferrite (Cux Ni1−x Fe2 O4 ), IR absorption bands are observed in the range of 600–400 cm−1 . The absorption band ν1 corresponds to the stretching vibration mode of Fe3+ –O2− in tetrahedral A-site, and ν2 corresponds to metal–oxygen vibrations in octahedral sites. The difference in the band position is expected because of the difference in the Fe3+ – O2− for the octahedral and tetrahedral complexes. From the inspection of the IR spectrum, it is very clear that as the concentration of Cu in Cux Ni1−x Fe2 O4 increases, vibrational frequencies ν1 and ν2 shift to lower side. The broadening of the bands can be attributed to Cu2+ ions occupying octahedral sites and some of the ions occupying tetrahedral sites. Shoulders are observed lower frequency bands ν2 which may be due to the Jahn–Teller effect. At low concentration of copper in copper nickel, ferrite splitting is less in ν2 band compared to that at higher concentration of copper in the samples. This is also supported by [24]. Ferrite metal ions are situated in two different sublattices, namely, tetrahedral (A sites) and octahedral (B sites), according to the geometrical configuration of the nearest oxygen neighbors. The band ν1 around 600 cm−1 is attributed to stretching vibration of tetrahedral complexes and the band ν2 around 400 cm−1 to that of octahedral complexes. It can be seen that the highfrequency band ν1 has a value of 597 cm−1 and the lower frequency band ν2 has 397 cm−1 . These values agree with the earlier observations [25] in which ν1 becomes 597 cm−1 and ν2 415 cm−1 . In inverse ferrites such as copper ferrite, the ν1 band is due to Fe3+ –O2− complex present at A sites


900

1000

1100


From the above relation, the vibrational frequencies decrease as the concentration of Cu2+ increases in copper nickel ferrite; this indicates that the force constant of the ions decreases which linearly depends on the internuclear separation. With the result of the substitution of Cu2+ ion in NiFe2 O4 , a shift in the lattice vibrational frequencies has been observed [27]. From this shift, it has been found that the force constants for the ions on the octahedral and tetrahedral sites depend linearly on the internuclear separations. 3.3 Morphological Studies

Fig. 7 SEM micrograph of Cu0.2 Ni0.8 Fe2 O4

The morphological and chemical analyses were performed using scanning electron microscopy (SEM). The SEM images were taken at different magnifications to study the morphology, and it can be seen from the SEM micrographs, Figs. 7, 8, and 9, that there are various compositions and that the morphology of the particles is very similar. They indicate that the particle size of the samples lies in the nanometer regime having a spherical shape and a narrow size distribution. The particle sharpness is more or less spherical with some cluster/agglomeration between the particles.

4 Conclusion


X-ray diffraction patterns confirmed the formation of single-phased cubic spinel structure without any impurity peak. The vibrational frequencies decrease as the concentration of Cu2+ increases in copper nickel ferrite; this indicates that the force constant of the ions decreases. With the result of the substitution of Cu2+ ion in NiFe2 O4 , a shift in the lattice vibrational frequencies has been observed. The SEM micrographs indicate that the particle size of the samples lies in the nanometer regime. The particle sharpness is more or less spherical with some cluster/agglomeration between the particles. The lattice parameter is varied with increasing Cu content in the mixed NiCu ferrite system due to the larger ionic radius of octahedral sites.

References


1. Darul, J., Nowicki, W.: Preparation and neutron diffraction study of polycrystalline Cu-Zn-Fe materials. Radiat. Phys. Chem. 78, s109–s111 (2009) 2. Goldman, A.: Modern Ferrite Technology. Marcel Dekker, New York (1993) 3. Alarifi, A., Deraz, N.M., Shaban, S.: Structural, morphological and magnetic properties of NiFe2O4 nano-particles. J. Alloys. Compd. 486(1- 2), 501–506 (2009) 4. Manova, E., Tsoncheva, T., Paneva, D., Mitov, I., Tenchev, K., Petrov, L.: Mechanochemically synthesized nano-dimensional


5.

6. 7.

8. 9.

10. 11.

12.

13.

14. 15.

iron-cobalt spinel oxides as catalysts for methanol decomposition. Appl. Catal. A 277(1–2), 119–127 (2004) Ferreira, T.A.S., Waerenborgh, J.C., Mendonsa, M.H.R.M., Nunes, M.R., Costa, F.M.: Structural and morphological characterization of FeCo2O4 and CoFe2O4 spinels prepared by a coprecipitation method. Solid State Sci. 5(2), 383–392 (2003) De Guire, M.: The cooling rate dependence of cation distributions in CoFe2O4. J. Appl. Phys. 65(8), 3167–3172 (1989) Li, S.: Cobalt-ferrite nanoparticles: structure, cation distributions, and magnetic properties. J. Appl. Phys. 87(9), 6223–6225 (2000) Stierstadt, K., Benz, H., Rechenberg, H.: Proc. int. conf. magnetism (Nottingham UK: Institute of Physics) p. 605 (1964) Shirsath, S.E., Toksha, B.G., Jadhav, K.M.: Structural and Magnetic Properties of In3+Substituted NiFe2O4. Mater. Chem. Phys. 117(1), 163–168 (2009) Ohnishi, H., Teranishi, T.: Crystal distortion in copper ferrite chromite series. J. Phys. Soc. Jpn. 16, 35–43 (1961) Jahn, H.A., Teller, E.: Stability of polyatomic molecules in degenerate electronic states I. Orbital degeneracy. Proc. R. Soc. London 161, 220–235 (1937) Wojtowicz, P.J.: Theoretical model for tetragonal-to-cubic phase transformations in transition metal spinels. Phys. Rev. 116, 32–45 (1959) Tailhades, P., Villette, C., Rousset, A., Kulkarni, G.U., Kannan K.R., Rao, C.N.R., Lenglet, M.: Cation migration and coercivity in mixed copper–cobalt spinel ferrite powders. J. Solid State Chem. 141, 56–61 (1998) Janicki, J., Pietrzak, J., Porebska, A., Suwalski, J.: Mössbauer study of copper ferrites. Phys. Status Solidi A 72, 95–98 (1982) Mazen, S.A., Elfalaky, A., Mohamed, A.Z., Hashem, H.A.M.: Effect of Ti4+ substitution in copper ferrite: An analogous study. Mater. Chem. Phys. 44(3), 293–299 (1996)

16. Tasca, J.E., Quincoces, C.E., Lavat, A., Alvarez, A.M., González, M.G.: Preparation and characterization of CuFe2 O4 bulk catalysts. Ceram. Int. 37, 803–812 (2011) 17. Mazen, S.A., Mansour, S.F., Zaki, H.M.: published on line 15 June 2003. Some physical and magnetic properties of Mg-Zn ferrite. Cryst. Res. Technol. 38(6), 471–478 (2003) 18. Tan, X., Li, G., Zhao, Y., Hu, C.: Effect of Cu content on the structure of Ni1−x Cux Fe2 O4 spinels. Mater. Res. Bull. 44, 2160–2168 (2009) 19. Manjura Hoque, S., Choudhury, A., Islam, F.: Characterization of Ni-Cu mixed spinel ferrite. J. Magn. Magn. Mater. 251(3), 292– 303 (2002) 20. Gabal, M.A., Al Angari, Y.M., Al-Juaid, S.S.: A study on Cu substituted Ni-Cu-Zn ferrites synthesized using egg-white. J. Alloys Compd. 492(1–2), 411–415 (2010) 21. Mahalakshmi, S., SrinivasaManja, K., Nithiyanantham, S.: Electrical properties of nanophase ferrites doped with rare earth ions. J. Supercond. Nov. Magn. 27(9), 2083–2088 (2004) 22. Cullity, B.D.: Elements of X-Ray Diffraction, p. 132. Addition Wesley, Boston (1959) 23. Waldron, R.D.: Infrared spectra of ferrites. Phys. Rev. 99, 1727 (1955) 24. KalaiSelvan, R., Augustin, C.O., Berchmans, L., Saraswathi, R.: Combustion synthesis of CaFe2 O4 . J. Mat. Res. Bull 38, 41–54 (2003) 25. Gilliot, B., Nivoix, V., Rousset, A.: Reactivity toward oxygen and certain distribution in copper manganese ferrite spinel fine powders. Mater. Chem. Phys. 48, 111 (1997) 26. Evans, B.J., Hafner, S.: Mössbauer Resonance of Fe57 in oxidic spinel containing Cu and Fe. J. Phys. Chem. Solids 29, 1573 (1968) 27. Srivastava, C.M., Srinivasan, T.T.: Effect of Jahn -Teller distribution on the lattice vibration frequencies of nickel ferrite. J. Appl. Phys. 53, 8148 (1982)