Effect of sintering temperature and thermoelectric power studies of the system MgFe2−xCrxO4
Graphical abstract
Introduction
Ferrites have been used by various industries as a catalyst for some industrially important catalytic reactions. The interesting physicochemical properties of ferrospinels arise from their ability to distribute the cations among the available tetrahedral (A) and octahedral [B] sites [1], [2], [3]. Magnesium ferrite is a magnetic material having an inverse spinel structure of which the degree of inversion depends upon the heat treatment. At present, several chemical methods including the solid state reaction, co-precipitation, sol–gel, citrate method have been developed to synthesize small particle sized ferrites [4], [5], [6].
The conventional ceramic method for the preparation of ferrites has certain limitations such as long heating schedule at high temperatures. Hence, in the present investigation chromium substituted magnesium ferrites have been prepared by the simple co-precipitation technique. The main important topic in the present study concerns the substitution of Cr3+ and the heat treatment on structure and thermoemf properties. The thermoelectric power studies also give the information about the type of conductivity, weather it is n-type or p-type.
Section snippets
Experimental
For the purpose of this investigation, various compositions of MgFe2−xCrxO4 (x = 0.0, 0.5, 1.0, 1.5 and 2.0) were prepared by the simple co-precipitation method [7], [8]. The high purity A.R. grade magnesium chloride, chromium chloride and iron chloride were weighed carefully to have the desired stoichiometric proportion. A mixed solution of the above chlorides was prepared in double distilled water. The precipitation was carried out at a controlled pH of ∼9.0 using a 10% NaOH solution. It was
X-ray diffraction studies
X-ray diffraction patterns of MgFeCrO4 at different temperatures are presented in Fig. 1. The peaks are indexed to the characteristic planes of pure spinel cubic structure. The diffraction peaks are found to be sharp and their intensity increases with increase in the sintering temperature. No other phase has been detected and (311) reflections appear to be more intense [9], [10], [11] consistent with observations for face centered cubic spinel.
Because the (311) diffraction peak at 900 °C is
Conclusions
The system MgFe2−xCrxO4 is synthesized by the simple co-precipitation method at controlled pH and exhibits the cubic spinel structure. The effect of sintering temperature on the observed structure influences the size of particles and consequently the grains. The calculated site radii and bond lengths show that the octahedral site radius is larger than the tetrahedral site. The FTIR spectrum shows two strong bands ν1 and ν2 in the expected region and the difference in their observed band
Acknowledgements
Authors PPH and VTV wish to acknowledge their sincere gratitude to UGC for Major Research Project [F. No. 32-289/2006 (SR)] New Delhi, India for their financial support.
References (20)
- et al.
Mater. Lett.
(2007) - et al.
Appl. Catal. A. General
(1998) - et al.
J. Mol. Catal. A: Chemical
(2004) - et al.
Mater. Chem. Phys.
(2009) - et al.
Mater. Lett.
(2000) - et al.
Mater. Chem. Phys.
(2006) J. Magn. Magn. Mater.
(2007)- et al.
Mater. Lett.
(2006) - et al.
J. Alloys Compd.
(2005) Philips Res.
(1968)
Cited by (10)
Influence of Zn<sup>2+</sup> ions on the structural and electrical properties of Mg<inf>1-x</inf>Zn<inf>x</inf>FeCrO<inf>4</inf> spinels
2016, Journal of Alloys and CompoundsCitation Excerpt :The average value for DW-H was found to be (9 ± 2) nm. Similar results have been reported for the NiFe2−xCrxO4 [21] and MgFe2−xCrxO4 [9] spinels. Values of DXRD and DW-H decrease first, pass through minimum then increase with Zn+2 content.
Thermoelectric properties of Ge-doped Bi<inf>85</inf>Sb<inf>15</inf> alloys at low temperatures
2014, Journal of Physics and Chemistry of SolidsCitation Excerpt :Since this energy conversion between heat and electricity is done by electrons in solids, thermoelectric devices exhibit a long life, but no pollution, no noise and spot cooling. Because it possesses various advantages, a broad search is under way to identify new thermoelectric materials with enhanced thermoelectric properties.[1–7] It is noteworthy that the considerable development of thermoelectrics mainly focuses on those materials which are usually used above room temperature.
Combustion synthesis of fine particle Zn-Ni ferrichromite by sol-gel method and their electrical properties
2012, Solid State SciencesCitation Excerpt :Hear the p-type conductivity is observed due to the hole exchange between Ni3+/Ni2+. Most of the charge carriers in the present system are holes which hop at the octahedral site [24,25]. The crystal structures of all samples are cubic spinel.
Infrared and structural studies of Mg <inf>1-x</inf>Zn <inf>x</inf>Fe <inf>2</inf>O <inf>4</inf> ferrites
2012, Physica B: Condensed MatterA study of dielectric relaxation properties of ZnFe<inf>2-x</inf>Bi<inf>x</inf>O<inf>4</inf> nano Ferrites synthesized by sol-gel combustion method
2020, Journal of Physics: Conference SeriesSynthesis of nanostructured pirochromite magnesium chromate with egg shell membrane template
2016, Applied Nanoscience (Switzerland)