Estimating the ionicity of an inverse spinel ferrite and the cation distribution of La-doped NiFe2O4 nanocrystals for gas sensing properties
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Nanocrystalline NiLaFe2O4 exhibit unique properties, which make them promising candidates for an inclusive range of applications such as actuators, magnetic resonance imaging, including gas sensing element due to its inverse spinel structure. It is requisite to revamp its ionicity, phase and magnetic properties. A primal approach has been chosen to fabricate NiLaFe2O4nanocrystals by co-precipitation technique at different calcination temperatures (300 °C, 400 °C, 500 °C, 600 °C) phase, and ionicity as well as magnetic properties. Changes in the structural characteristics of as-synthesized samples have been found by the inclusion of rare-earth elements in X-ray diffraction studies. Fourier transform infrared spectral studies embrace two absorption bands peaked at 400 and 500 cm−1representing the octahedral and tetrahedral sites. The transmission electron microscopy analysis depicts the tailored morphology of as-synthesized nanocrystal. The magnetization was determined by vibrating sample magnetometer and found that Hc increases with decrease in Ms and magnetostriction coefficient. These results can be partially described by the frailer nature of La3+–Fe3+ions which are equated to Fe3+–Fe2+ interaction. A model for inverse spinel ferrite has been used which refers as O2p itinerant electron model. The magnetization and the cation distributions of the La doped inverse spinel ferrites were elucidated using this model. The sensor designates with high selectivity, repeatability and fast transition at room temperature (305 K) towards ammonia gas in particular when related to ethanol, acetone and toluene. Low deposition cost makes it competent for developing a cost-effective ammonia sensor.
The author (S. Jerome Das) is grateful to the Management of Loyola College, Chennai-34 for awarding Loyola College TOI project (3LCTOI14PHY002) and acknowledges the technical help rendered by sophisticated Analytical Instrumentation Facility, Cochin for TEM and UV analysis. The authors are grateful to Dr. Jeyadheepan, Assistant Professor, Multifunctional Materials and Devices lab, Sastra Deemed University for Gas sensor studies.
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