In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Nanomaterials and the environment: A review for the biennium 2008-2010

Recent developments and trends of sol-gel auto-combustion method for spinel ferrite nanomaterial synthesis are briefly discussed and critically analyzed. The analysis of various parameters of reaction which could be used for better understanding of synthesis process and control of microstructure and property of spinel ferrite nanopowder products was the main objective of this review article. Special attention was paid to variety of particle size and phase purity. For these purposes the correlation between complexant, oxygen balance and combustion process chemical additives, as well as heating mechanism and atmosphere, was established. These results are relevant from standpoints of both application and processing of ferrites.

Sol-gel auto-combustion synthesis of spinel-type ferrite nanomaterials

The demand for portable gas sensors is increasing following the progress in the electronics industry; there is an equal need to increase the quality of gas sensors. Spinel ferrites have been used as electronic materials for more than 50 years and offer a suitable ceramic base for the gas sensor market. They are simple, low cost, and compared to other gas sensors have structural and compositional versatility. This review highlights the recent developments and shows the potential of the spinel ferrites on gas sensor technology. Sensing mechanisms for a range of gasses and humidity are explained for n-type, p-type, mixed and substituted spinel ferrite gas sensors. The change in conduction mechanism is discussed outlining electronic and chemical sensitization that both increase the conductivity. Some cation substitutions are shown to change the oxidation state, thereby increasing sensitivity, but noble metals are shown to chemically sensitize spinel ferrites. This review surveys synthesis methods for producing spinel ferrites and discusses future prospects for further improvements.

Spinel ferrite oxide semiconductor gas sensors

Resistance-based H2S gas sensors using metal oxide nanostructures: A review of recent advances.

Studies on the preparation and ethanol gas sensing properties of spinel Zn0.6Mn0.4Fe2O4 nanomaterials

In this paper, the structural and gas sensing properties of nanocrystalline La0.7Pb0.3Fe0.4Ni0.6O3 was prepared by a sol–gel citrate method. The structural characteristics of the material were studied by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD pattern shows a nanocrystalline solid solution of La0.7Pb0.3Fe0.4Ni0.6O3 with a perovskite phase. The gas sensing properties were studied for different reducing gases such as H2S, ethanol, CO and LPG. The La0.7Pb0.3Fe0.4Ni0.6O3 powder showed large response to H2S gas at an operating temperature 250 °C. Further improvement in response was achieved by the addition of 0.5 wt% Pd to La0.7Pb0.3Fe0.4Ni0.6O3. The sensor showed a good response to 150 ppm H2S gas at an operating temperature 200 °C.

H2S sensing characteristics of La0.7Pb0.3Fe0.4Ni0.6O3 based nanocrystalline thick film gas sensor

Semiconducting Zinc stannate, Zn2SnO4, is an important n-type semiconductor with a large band gap of 3.6 eV [1], which is often called zinc tin oxide (ZTO) having face – centred cubic spinel structure. The compound has been successfully prepared by simple method called sol gel citrate method followed by calcinations. The nanocomposite was characterized by means of x-ray powder diffraction. Additionally, sensor performance of undoped and surface modified by 5 wt % copper oxide over ZTO were studied under different operating temperature and different reducing gases such as ethanol, H2S, CO and LPG. The result reveals that material exhibit excellent sensitivity and selectivity toward carbon monoxide gas at 1800C proving their applicability in gas sensors.

https://www.jetir.org/papers/JETIRDI06085.pdf

Gas sensing properties of cuo modified zinc stannate nanomaterial prepared by sol – gel method

Polycrystalline samples of Co1–xZnxFe2O4 with stoichiometric proportion (x) varying from 0.2 to 0.8 were synthesized through the sol-gel citrate method. The structure and morphology were characterized by X-ray powder diffraction and Scanning Electron Microscopy. XRD studies revealed the formation of single phase spinel cubical structure. The average particle size of synthesized sample is estimated as from 35 to 40 nm. The gas sensing performance of the unmodified and surface modified films was tested for various gases such as H2S, Ethanol, LPG and CO. Co0.2Zn0.8Fe2O4 powder showed large response to 200 ppm ethanol gas at an operating temperature 2200C. The sensitivity, selectivity of Co0.2Zn0.8Fe2O4 thick films was measured.

https://www.jetir.org/papers/JETIRDI06076.pdf

A. V. Kadu

Papers

Studies on the preparation and ethanol gas sensing properties of spinel Zn0.6Mn0.4Fe2O4 nanomaterials

H2S sensing characteristics of La0.7Pb0.3Fe0.4Ni0.6O3 based nanocrystalline thick film gas sensor

Gas sensing properties of cuo modified zinc stannate nanomaterial prepared by sol – gel method

INFLUENCE OF Zn SUBSTITUTION ON THE STRUCTURAL AND GAS SENSING PROPERTIES OF Co1-xZnxFe2O4 NANO-FERRITES