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Synthesis and characterization of cadmium ferrite
Materials Chemistry and Physics 112 (2008) 24–26
Contents lists available at ScienceDirect
Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys
Materials science communication
Synthesis and characterization of cadmium ferrite P.K. Nayak ∗ A.K. College of Engineering, Krishnankoil, Tamilnadu-626 190, India
a r t i c l e
i n f o
Article history: Received 7 September 2007 Received in revised form 30 March 2008 Accepted 14 May 2008 Keywords: Magnetic materials Electron resonance Characterization methods
a b s t r a c t This report presents the synthesis of cadmium ferrite (CdFe2 O4 ) by combustion method and its subsequent characterization by using X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and electron spin resonance (ESR) techniques. The XRD results confirm the cubic spinel phase formation with the particle size of 106 nm, which has increased to 115 nm on further heating at higher temperature. By using VSM, a complex magnetic structure was observed with significant change on heated sample. The ESR measurements for cadmium ferrite sample at room temperature and low temperature were also found to be significantly different, especially after heat-treatment. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Recently, cadmium ferrite (CdFe2 O4 ) has attracted attention due to its multiple applications in various fields [1,2]. Bulk cadmium ferrite has been considered as a normal spinel structure with cadmium ions occupying the tetrahedral sites, and has been categorised as antiferromagnets [3]. It has been reported that cadmium substituted ferrites behave as n-type semiconductor, and the Seebeck coefficient gradually decreases with increase in cadmium content [4]. A study conducted on substitution of cadmium in high permeability lithium ferrite (a high potential microwave applicable material) indicates that the lattice parameter increases with increase in cadmium content, governed by large grain size and small anisotropy constant [5]. An investigation made by ul-Islam et al. results in the proposition for the use of cadmium zinc ferrite as microwave field attenuator, especially in the radiative atmosphere and in read/write devices [6]. Subsequent studies [7] by the same group on electrical properties of cadmium substituted copper ferrites provided a very good correlation between resistivity and thermopower. Earlier studies indicate that a very narrow range of temperature and thermal treatment time is needed for obtaining nano-sized cadmium ferrites [8,9]. FT-IR studies on cadmium substituted magnetite by Gillot et al. reveals that with the increase in cadmium content, the number of absorption bands decreases and the spectrum is slightly different from that of the unoxidised spinels of same composition [10]. One interesting report indicates that cadmium–iron based complex oxides show a high sensitiv-
ity and selectivity to ethanol gas over carbon monoxide, hydrogen and isobutene [11]. In this report, we have presented the combustion synthesis technique for synthesising cadmium ferrite and their subsequent characterization by XRD, VSM and ESR techniques. 2. Experimental 2.1. Synthesis of cadmium ferrite A combustion method has been adopted in order to synthesise cadmium ferrite. AR grade iron nitrates and cadmium nitrates were weighed separately with a ratio of 2:1 and dissolved in de-ionised water. A 3 M citric acid solution (50 ml) was added to each metal solution (50 ml) and heated at 40 ◦ C for approximately 20 min with continuous stirring. The final mixture was slowly evaporated until highly viscous gel was formed. The resulting gel was left for continuous heating until the completion of the reaction was achieved by a self-propagated process. The final residue is in powdered form and was collected for subsequent investigation. 2.2. Characterization of cadmium ferrite As-synthesised powder sample was heat treated at 1000 ◦ C for 2 h. Both these samples (as synthesised and heat treated) were subjected to X-ray diffraction using Cu K␣ lines. Simultaneous TG-DTA data were recorded on a Shimadzu DTG-50 thermal analyser under static air at a heating rate of 10 ◦ K min−1 and platinum crucibles were used with ␣-Al2 O3 as the reference material. Using a vibrating sample magnetometer, magnetization measurements were carried out for obtaining M-H loops. For ESR measurements, the powdered sample was transferred into a quartz tube, and the spectra were recorded at room temperature as well as at liquid nitrogen temperature (at 77 K). The ESR spectrometer (Varion E–112) used for this purpose, was operated at X-band frequencies ( = 9.1 GHz) with a 100 kHz field modulation for obtaining first derivative ESR spectra.
3. Results and discussion ∗ Present address: Department of High Energy Physics, Tata Institute of Fundamental Research, Mumbai-400005, India. Tel.: +91 22 22782367. E-mail address: [email protected]. 0254-0584/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2008.05.018
X-ray diffraction spectra collected for the as-synthesised sample and heated at 1000 ◦ C have been provided in Fig. 1(a) and (b), respectively. Crystallite size of the as-synthesised sample was
P.K. Nayak / Materials Chemistry and Physics 112 (2008) 24–26
25
Fig. 3. VSM spectrum of cadmium ferrite.
found to be 106 nm, which on heating increases to 115 nm. The calculated unit cell parameter [12] was found to be 8.9792 A˚ for as-synthesised samples, which is in accordance with other ˚ [11]. However, it decreases reported bulk cadmium ferrite (8.70 A) to 8.6859 A˚ for heat-treatment sample. Simultaneous TG-DTA spectra for the as-synthesised sample have been presented in Fig. 2. The TG curve indicates the com-
plete spinel formation at around 400 ◦ C (after about 20% mass loss), which is mostly due to evaporation of additional nitrate. The respective DTA graphs indicate an exothermic phenomena at about 350–410 ◦ C. Furthermore, we would like to mention here that a group has already [11] reported that there is no observable change in the temperature range 550–1000 ◦ C for cadmium ferrite. The variation in saturation magnetization (Ms ) is provided in Fig. 3 for as-synthesised as well as heat-treated sample. A prominent hysteresis curve was obtained for as-synthesised sample though the measured Ms value was found to be only 0.135 emu g−1 at 1 kG. However, there is an interesting scenario observed for heat-treated sample with saturation magnetization value of 0.046 emu g−1 , with a narrow hysteresis. In this case, the measured Ms value was comparatively very low, but far from saturation even at a field of 10 kG. The obtained ESR spectra collected at room temperature and liquid nitrogen temperature have been provided in Fig. 4 along with their corresponding ESR parameters. For as-synthesised sample, the observed ESR line with g-value of 2.4356 looks very much similar to other reports [13–16]. Eissa and Hassib [13] reported g-value of about 2.0088 for cadmium ferrite substituted with 20% magnesium whereas Chand et al. [14] reported a g-value of about 2.65 for a Ti-substituted nickel ferrite (Ni1.005 Ti0.005 Fe1.99 O4 ) sample recently. However, the above-observed g-value for as-synthesised
Fig. 2. Simultaneous TG-DTA spectrum of as-synthesised sample.
Fig. 4. ESR spectra of cadmium ferrite (a) As-synthesized and (b) heated at 1000 ◦ C.
Fig. 1. (a) XRD spectrum of CdFe2 O4 (as synthesised) and (b) XRD spectrum of heattreated CdFe2 O4 (2 h at 1000 ◦ C).
26
P.K. Nayak / Materials Chemistry and Physics 112 (2008) 24–26
sample is found to be increased to 4.3047 for heat-treated sample, which is an indication of increase in ferromagnetism. Moreover, on lowering the temperature the g-value increase from 2.4356 to 2.5086 for as-synthesised sample indicating the increase in the internal field, which is seems to be higher than expected for such a system having magnetic iron spins. This may be attributed to paramagnetic effect due to invisible ferric iron that increases magnetization which might produce induced magnetic field to the applied field [17,18]. However, in case of heat-treated sample, there is reasonably less variation between room temperature and low temperature ESR spectra. As mentioned earlier, it is expected that the low temperature ESR data is supposed to provide some information on the types of changes. In case of heat-treated sample, apparently negligible change in the g-value at 77 K of the sample strongly support and confirms that changes are irreversible. It should be noted that an ESR signal near g = 2 is not expected in the anti-ferromagnetic state so that the association of the ESR signal with the uncompensated surface spins inferred above from the observations is an important result. The effective g-value is found to be 2.5086 for this sample, which is not close to the free electron g-value of 2.0023 of typical S state ions. Hence, iron ion in this compound is high spin ferric (S state) magnetic ion. This observed large increase in line-width of the ESR spectra may be correlated to the distribution of exchange interaction [17,18]. Further, it can be noticed from Fig. 4 that there is a sharp decrease in line-width on heating the as-synthesised sample. This can be correlated to a recent report [9] that the presence and amount of ferrous ion in the octahedral site is responsible for the line broadening in the ESR spectra, which is up to some extent we believe, is the reason here. Moreover, the observed resonance field of assynthesised sample is at 2660 G, which has decreased to 2600 G with measuring at low temperature. This observed decrease in resonance field of the ESR spectrum can be correlated to the distribution of exchange interaction [5–7]. The change in resonance field shift (about 60 G) can be considered as an indication to the induced field (exchange anisotropy field), which may be due to the disorder of the studied magnetic systems. On measuring at low temperature, the line-width found to be increases significantly from 3600 to 4480 G, which is attributed to spin frustrations, arising from possible anti-ferromagnetic interaction among the neighbouring spins in magnetic particles in a sample and can partially be connected to anti-ferromagnetic interactions between the magnetic clusters related to randomly frozen spin profile [8]. In supplementary, we would like to mention here that due to large neutron cross-section of cadmium, it is difficult to study this cadmium ferrite by using
neutron diffraction. Further extensive ESR studies involving effect of calcination temperature is being attempted and will be reported soon. 4. Conclusion In this report, an attempt was made to synthesise cadmium ferrite by a simple combustion method, and was found to be very much suitable for obtaining cubic cadmium ferrite spinel. The initial particle size was 106 nm, which on heating has increased to 115 nm. We have observed a complex magnetic structure of the Fe3+ moments that result in a (strong) non-linearity of the increase of magnetization with increasing magnetic field. ESR results show varying effect of heating for g-values along with other parameters like line-width and resonance field. Low temperature ESR measurement confirms the presence of ordering in cadmium ferrite spinel. Further study is being extended towards the synthesis and characterization of substituted rare-earth elements by various techniques. Acknowledgements Thanks are due to Dr. R. Jothiramalingam, Department of Chemistry, Indian Institute of Technology, Chennai and also to, RSIF, Chennai, for various measurements. References [1] O. Silva, P.C. Morais, J. Magn. Magn. Mater. 289 (2005) 136. [2] M. Yokoyama, E. Ohta, T. Sato, T. Sato, J. Magn. Magn. Mater. 183 (1998) 173. [3] G. Albanese, A. Deriu, G. Calestani, F. Leccabue, B.E. Wattas, J. Mater. Sci. 27 (1992) 6146. [4] D. Ravindar, S.S. Rao, P. Shalini, Mater. Lett. 57 (2003) 4040. [5] S.S. Bellad, et al., Bull. Mater. Sci. 23 (2000) 83. [6] M. ul-Islam, et al., J. Nat. Sci. Math. 38 (1998) 189. [7] M. ul-Islam, T. Abbas, M.A. Chaudhury, Mater. Lett. 53 (2002) 30. [8] K. Keneko, T. Takei, Y. Tamaura, T. Kanzaki, T. Katsura, Bull. Chem. Soc. Jpn. 47 (1974) 1646. [9] W. Wolski, E. Wolski, J. Kaczmarck, J. Solid State Chem. 110 (1994) 70. [10] B. Gillot, D. Thiebaut, M. Laarj, Thermochim. Acta 342 (1999) 167. [11] Z. Tianshu, P. Hing, Z. Jiancheng, K. Lingbing, Mater. Chem. Phys. 61 (1999) 192. [12] S.C. Chanda, A. Manna, V. Vijayan, P.K. Nayak, M. Ashok, H.N. Acharya, Mater. Lett. 61 (2007) 5092. [13] N.A. Eissa, A. Hassib, Hyp. Int. 28 (1986) 843. [14] P. Chand, R.C. Srivastava, A. Upadhyay, J. Alloys Compd. 460 (2008) 108. [15] P.K. Nayak, J. Ramalingam, Inorg. Chem.: Indian J. 2 (1) (2007) (Available in internet on 7th February, 2007). [16] P.K. Nayak, J. Ramalingam, Int. J. Mod. Phys. B. (in press). [17] N.E. Whitehead, T. Atushi, K. Tazaki, M. Ikeya, Electron. J. Biotechnol. 7 (2004) 290. [18] O.M. Hemeda, J. Magn. Magn. Mater. 251 (2002) 50.
Contents lists available at ScienceDirect
Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys
Materials science communication
Synthesis and characterization of cadmium ferrite P.K. Nayak ∗ A.K. College of Engineering, Krishnankoil, Tamilnadu-626 190, India
a r t i c l e
i n f o
Article history: Received 7 September 2007 Received in revised form 30 March 2008 Accepted 14 May 2008 Keywords: Magnetic materials Electron resonance Characterization methods
a b s t r a c t This report presents the synthesis of cadmium ferrite (CdFe2 O4 ) by combustion method and its subsequent characterization by using X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and electron spin resonance (ESR) techniques. The XRD results confirm the cubic spinel phase formation with the particle size of 106 nm, which has increased to 115 nm on further heating at higher temperature. By using VSM, a complex magnetic structure was observed with significant change on heated sample. The ESR measurements for cadmium ferrite sample at room temperature and low temperature were also found to be significantly different, especially after heat-treatment. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Recently, cadmium ferrite (CdFe2 O4 ) has attracted attention due to its multiple applications in various fields [1,2]. Bulk cadmium ferrite has been considered as a normal spinel structure with cadmium ions occupying the tetrahedral sites, and has been categorised as antiferromagnets [3]. It has been reported that cadmium substituted ferrites behave as n-type semiconductor, and the Seebeck coefficient gradually decreases with increase in cadmium content [4]. A study conducted on substitution of cadmium in high permeability lithium ferrite (a high potential microwave applicable material) indicates that the lattice parameter increases with increase in cadmium content, governed by large grain size and small anisotropy constant [5]. An investigation made by ul-Islam et al. results in the proposition for the use of cadmium zinc ferrite as microwave field attenuator, especially in the radiative atmosphere and in read/write devices [6]. Subsequent studies [7] by the same group on electrical properties of cadmium substituted copper ferrites provided a very good correlation between resistivity and thermopower. Earlier studies indicate that a very narrow range of temperature and thermal treatment time is needed for obtaining nano-sized cadmium ferrites [8,9]. FT-IR studies on cadmium substituted magnetite by Gillot et al. reveals that with the increase in cadmium content, the number of absorption bands decreases and the spectrum is slightly different from that of the unoxidised spinels of same composition [10]. One interesting report indicates that cadmium–iron based complex oxides show a high sensitiv-
ity and selectivity to ethanol gas over carbon monoxide, hydrogen and isobutene [11]. In this report, we have presented the combustion synthesis technique for synthesising cadmium ferrite and their subsequent characterization by XRD, VSM and ESR techniques. 2. Experimental 2.1. Synthesis of cadmium ferrite A combustion method has been adopted in order to synthesise cadmium ferrite. AR grade iron nitrates and cadmium nitrates were weighed separately with a ratio of 2:1 and dissolved in de-ionised water. A 3 M citric acid solution (50 ml) was added to each metal solution (50 ml) and heated at 40 ◦ C for approximately 20 min with continuous stirring. The final mixture was slowly evaporated until highly viscous gel was formed. The resulting gel was left for continuous heating until the completion of the reaction was achieved by a self-propagated process. The final residue is in powdered form and was collected for subsequent investigation. 2.2. Characterization of cadmium ferrite As-synthesised powder sample was heat treated at 1000 ◦ C for 2 h. Both these samples (as synthesised and heat treated) were subjected to X-ray diffraction using Cu K␣ lines. Simultaneous TG-DTA data were recorded on a Shimadzu DTG-50 thermal analyser under static air at a heating rate of 10 ◦ K min−1 and platinum crucibles were used with ␣-Al2 O3 as the reference material. Using a vibrating sample magnetometer, magnetization measurements were carried out for obtaining M-H loops. For ESR measurements, the powdered sample was transferred into a quartz tube, and the spectra were recorded at room temperature as well as at liquid nitrogen temperature (at 77 K). The ESR spectrometer (Varion E–112) used for this purpose, was operated at X-band frequencies ( = 9.1 GHz) with a 100 kHz field modulation for obtaining first derivative ESR spectra.
3. Results and discussion ∗ Present address: Department of High Energy Physics, Tata Institute of Fundamental Research, Mumbai-400005, India. Tel.: +91 22 22782367. E-mail address: [email protected]. 0254-0584/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2008.05.018
X-ray diffraction spectra collected for the as-synthesised sample and heated at 1000 ◦ C have been provided in Fig. 1(a) and (b), respectively. Crystallite size of the as-synthesised sample was
P.K. Nayak / Materials Chemistry and Physics 112 (2008) 24–26
25
Fig. 3. VSM spectrum of cadmium ferrite.
found to be 106 nm, which on heating increases to 115 nm. The calculated unit cell parameter [12] was found to be 8.9792 A˚ for as-synthesised samples, which is in accordance with other ˚ [11]. However, it decreases reported bulk cadmium ferrite (8.70 A) to 8.6859 A˚ for heat-treatment sample. Simultaneous TG-DTA spectra for the as-synthesised sample have been presented in Fig. 2. The TG curve indicates the com-
plete spinel formation at around 400 ◦ C (after about 20% mass loss), which is mostly due to evaporation of additional nitrate. The respective DTA graphs indicate an exothermic phenomena at about 350–410 ◦ C. Furthermore, we would like to mention here that a group has already [11] reported that there is no observable change in the temperature range 550–1000 ◦ C for cadmium ferrite. The variation in saturation magnetization (Ms ) is provided in Fig. 3 for as-synthesised as well as heat-treated sample. A prominent hysteresis curve was obtained for as-synthesised sample though the measured Ms value was found to be only 0.135 emu g−1 at 1 kG. However, there is an interesting scenario observed for heat-treated sample with saturation magnetization value of 0.046 emu g−1 , with a narrow hysteresis. In this case, the measured Ms value was comparatively very low, but far from saturation even at a field of 10 kG. The obtained ESR spectra collected at room temperature and liquid nitrogen temperature have been provided in Fig. 4 along with their corresponding ESR parameters. For as-synthesised sample, the observed ESR line with g-value of 2.4356 looks very much similar to other reports [13–16]. Eissa and Hassib [13] reported g-value of about 2.0088 for cadmium ferrite substituted with 20% magnesium whereas Chand et al. [14] reported a g-value of about 2.65 for a Ti-substituted nickel ferrite (Ni1.005 Ti0.005 Fe1.99 O4 ) sample recently. However, the above-observed g-value for as-synthesised
Fig. 2. Simultaneous TG-DTA spectrum of as-synthesised sample.
Fig. 4. ESR spectra of cadmium ferrite (a) As-synthesized and (b) heated at 1000 ◦ C.
Fig. 1. (a) XRD spectrum of CdFe2 O4 (as synthesised) and (b) XRD spectrum of heattreated CdFe2 O4 (2 h at 1000 ◦ C).
26
P.K. Nayak / Materials Chemistry and Physics 112 (2008) 24–26
sample is found to be increased to 4.3047 for heat-treated sample, which is an indication of increase in ferromagnetism. Moreover, on lowering the temperature the g-value increase from 2.4356 to 2.5086 for as-synthesised sample indicating the increase in the internal field, which is seems to be higher than expected for such a system having magnetic iron spins. This may be attributed to paramagnetic effect due to invisible ferric iron that increases magnetization which might produce induced magnetic field to the applied field [17,18]. However, in case of heat-treated sample, there is reasonably less variation between room temperature and low temperature ESR spectra. As mentioned earlier, it is expected that the low temperature ESR data is supposed to provide some information on the types of changes. In case of heat-treated sample, apparently negligible change in the g-value at 77 K of the sample strongly support and confirms that changes are irreversible. It should be noted that an ESR signal near g = 2 is not expected in the anti-ferromagnetic state so that the association of the ESR signal with the uncompensated surface spins inferred above from the observations is an important result. The effective g-value is found to be 2.5086 for this sample, which is not close to the free electron g-value of 2.0023 of typical S state ions. Hence, iron ion in this compound is high spin ferric (S state) magnetic ion. This observed large increase in line-width of the ESR spectra may be correlated to the distribution of exchange interaction [17,18]. Further, it can be noticed from Fig. 4 that there is a sharp decrease in line-width on heating the as-synthesised sample. This can be correlated to a recent report [9] that the presence and amount of ferrous ion in the octahedral site is responsible for the line broadening in the ESR spectra, which is up to some extent we believe, is the reason here. Moreover, the observed resonance field of assynthesised sample is at 2660 G, which has decreased to 2600 G with measuring at low temperature. This observed decrease in resonance field of the ESR spectrum can be correlated to the distribution of exchange interaction [5–7]. The change in resonance field shift (about 60 G) can be considered as an indication to the induced field (exchange anisotropy field), which may be due to the disorder of the studied magnetic systems. On measuring at low temperature, the line-width found to be increases significantly from 3600 to 4480 G, which is attributed to spin frustrations, arising from possible anti-ferromagnetic interaction among the neighbouring spins in magnetic particles in a sample and can partially be connected to anti-ferromagnetic interactions between the magnetic clusters related to randomly frozen spin profile [8]. In supplementary, we would like to mention here that due to large neutron cross-section of cadmium, it is difficult to study this cadmium ferrite by using
neutron diffraction. Further extensive ESR studies involving effect of calcination temperature is being attempted and will be reported soon. 4. Conclusion In this report, an attempt was made to synthesise cadmium ferrite by a simple combustion method, and was found to be very much suitable for obtaining cubic cadmium ferrite spinel. The initial particle size was 106 nm, which on heating has increased to 115 nm. We have observed a complex magnetic structure of the Fe3+ moments that result in a (strong) non-linearity of the increase of magnetization with increasing magnetic field. ESR results show varying effect of heating for g-values along with other parameters like line-width and resonance field. Low temperature ESR measurement confirms the presence of ordering in cadmium ferrite spinel. Further study is being extended towards the synthesis and characterization of substituted rare-earth elements by various techniques. Acknowledgements Thanks are due to Dr. R. Jothiramalingam, Department of Chemistry, Indian Institute of Technology, Chennai and also to, RSIF, Chennai, for various measurements. References [1] O. Silva, P.C. Morais, J. Magn. Magn. Mater. 289 (2005) 136. [2] M. Yokoyama, E. Ohta, T. Sato, T. Sato, J. Magn. Magn. Mater. 183 (1998) 173. [3] G. Albanese, A. Deriu, G. Calestani, F. Leccabue, B.E. Wattas, J. Mater. Sci. 27 (1992) 6146. [4] D. Ravindar, S.S. Rao, P. Shalini, Mater. Lett. 57 (2003) 4040. [5] S.S. Bellad, et al., Bull. Mater. Sci. 23 (2000) 83. [6] M. ul-Islam, et al., J. Nat. Sci. Math. 38 (1998) 189. [7] M. ul-Islam, T. Abbas, M.A. Chaudhury, Mater. Lett. 53 (2002) 30. [8] K. Keneko, T. Takei, Y. Tamaura, T. Kanzaki, T. Katsura, Bull. Chem. Soc. Jpn. 47 (1974) 1646. [9] W. Wolski, E. Wolski, J. Kaczmarck, J. Solid State Chem. 110 (1994) 70. [10] B. Gillot, D. Thiebaut, M. Laarj, Thermochim. Acta 342 (1999) 167. [11] Z. Tianshu, P. Hing, Z. Jiancheng, K. Lingbing, Mater. Chem. Phys. 61 (1999) 192. [12] S.C. Chanda, A. Manna, V. Vijayan, P.K. Nayak, M. Ashok, H.N. Acharya, Mater. Lett. 61 (2007) 5092. [13] N.A. Eissa, A. Hassib, Hyp. Int. 28 (1986) 843. [14] P. Chand, R.C. Srivastava, A. Upadhyay, J. Alloys Compd. 460 (2008) 108. [15] P.K. Nayak, J. Ramalingam, Inorg. Chem.: Indian J. 2 (1) (2007) (Available in internet on 7th February, 2007). [16] P.K. Nayak, J. Ramalingam, Int. J. Mod. Phys. B. (in press). [17] N.E. Whitehead, T. Atushi, K. Tazaki, M. Ikeya, Electron. J. Biotechnol. 7 (2004) 290. [18] O.M. Hemeda, J. Magn. Magn. Mater. 251 (2002) 50.