Influence of Pellet Compaction Pressure on the Physical Properties of La0.7Ba0.3MnO3 Manganite

Abstract

Perovskite manganite La 0.7 Ba 0.3 MnO 3 , synthesized by ionic coordination reaction method (ICR) was compacted into pellets under different compaction pressures (P c ) and sintered at a temperature of 1150°C for 10h under a flow of O 2 . X-ray diffraction (XRD) data reveal that the samples can present simultaneously two phases -a rhombohedral structure with space group R3c and an orthorhombic structure with space group Pnma. Scanning electron microscopy (SEM) images show that, for this sintering temperature, the particle size and shape can be modified depending on the compaction pressure (P c ). Magnetization measurements show that the saturation magnetization and Curie temperature increase with P c . The enhancement of the ferromagnetic properties of perovskite manganites La 0.7 Ba 0.3 MnO 3 as a function of the compaction pressure is explained by an increase in the rhombohedral/orthorhombic structure ratio caused by this effect.

The Electrochemical Corrosion Behaviour of compacted (Bi, Pb)-2223 superconductors in Aqueous Solutions

“…The porosity of (Bi, Pb)-2223 superconductor electrodes compacted at different pressure were determined using the equation (p = [1-𝜌 / 𝜌 th ] x 100) where 𝜌 is the experimental density and the 𝜌 th is theoretical density of Bi, Pb superconductor phase (𝜌 th = 6.3 g/cm 3 ) [17]. It is clear from Table 2 that increasing compaction up to 1.4 GPa decreases the porosity of the superconductor's electrodes which is in a good accordance with the conclusion reported previously that indicated that the pressed materials show reduced porosity after pressing [14,15]. However, no change in porosity was observed after 1.4 GPa compaction, which could be attributed to deformation of the plate-like morphology as shown in the SEM micrograph.…”

“…According to zkurt et al [13], the ceramic nature of Bi-2223 high-temperature superconductors limit their practical application: they are very fragile, extremely anisotropic, have a low critical current density at high temperatures, and are di cult to manufacture in a single phase. Chemical storage or removal may depend on a combination of physical properties, such as porosity and surface area, as well as chemical properties, such as surface reactions [14,15]. Given the broad range of chemicals that may be encountered, including highly acidic/acid-forming gases as well as neutral and alkaline chemicals, materials must be developed with certain functionalities capable of retarding the corrosion of different classes of chemicals.…”