In the present work, we have illustrated the physics of the multifunctional characteristics of nano-crystalline LaFeO3 powder prepared using auto-combustion synthesis. The synthesized powders were phase pure and crystallized into centro-symmetric Pnma space group. The temperature dependence of dielectric constant of pure LaFeO3 exhibits dielectric maxima similar to that observed in ferroelectric ceramics with non-centrosymmetric point group. The dielectric relaxation of LaFeO3 correlates well with small polaron conduction. The occurrence of polarization hysteresis in LaFeO3 (with centro-symmetric Pnma space group) is thought to be spin current induced type. The canting of the Fe3+ spins induce weak ferromagnetism in nano-crystalline LaFeO3. Room temperature saturation magnetization of pure LaFeO3 is reported to be 3.0 emu/g. Due to the presence of both ferromagnetic as well as polarization ordering, LaFeO3 behaves like a single phase multiferroic ceramics. The magneto-electric coupling in this system has been demonstrated through the magneto-dielectric measurements which yield about 0.8% dielectric tuning (at 10 kHz) with the application of 2 T magnetic field. As a typical application of the synthesized nano-crystalline LaFeO3 powder, we have studied its butane sensing characteristics. The efficient butane sensing characteristics have been correlated to their catalytic activity towards oxidation of butane. Through X-ray photoelectron spectroscopy analyses, we detect the surface adsorbed oxygen species on LaFeO3 surface. Surface adsorbed oxygen species play major role in their low temperature butane sensing. Finally, we have hypothesized that the desorbed H2O and O2 (originate from surface adsorbed hydroxyl and oxygen) initiate the catalytic oxidative dehydrogenation of n-butane resulting in weakening of the electrostatics of the gas molecules.
LaFeO 3 , a nontoxic and thermally stable compound, when prepared of small crystallites offers tailored magnetic and magnetoelectric properties at room temperature. In this article, we describe synthesis of a phase pure LaFeO 3 of nanocrystallites with a bonded carbon surface layer from a liquid precursor at moderate temperature in air. The results demonstrate that, upon sonication and microwave heating, the metal ions La 3+ and Fe 3+ in an inorganic-organic precursor cluster and grow into LaFeO 3 crystallites in a specific shape of nanoplates, typically 40-150 nm in width and 15-25 nm in thickness, at moderate temperature ∼700 C in ambient air. The stable phase LaFeO 3 stands in an orthorhombic crystal structure (Pnma space group), on sintering to obtain useful ferroelectric properties in a dense pellet. At room temperature, a sintered pellet (at 950 C for 4 h) measures a wide ferroelectric hysteresis loop, showing a polarization of 2.05 C/cm 2 , remnant polarization of 0.78 C/cm 2 , and coercivity 7.65 kV/cm for an applied electric field up to 18 kV/cm (at 500 Hz). These values are compatible to those known in important granular multiferroics such as BiFeO 3 and composites.
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