We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO₃ (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO_2.5) and conducting perovskite (SrCoO_3−δ) depending on the oxygen content. The current–voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoO_x thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO_2.5.

The effect of chemical activators on the properties of activated carbon from sago waste was conducted in this study by using ZnCl₂, H₃PO₄, KOH, and KMnO₄ chemical solutions. The carbonized sago waste was added to each chemical solution, boiled at 85 °C for 4 h, and heated at 600 °C for 3 h. The porosity, microstructural, proximate, and surface chemistry analyses were carried out using nitrogen adsorption with employing the Brunauer Emmett Teller (BET) method and the Barret-Joyner-Halenda (BJH) calculation, scanning electron microscopy by using energy dispersive spectroscopy, X-ray diffractometer, simultaneous thermogravimetric analysis system, and the Fourier-transform infrared spectroscopy. The results showed that the activated carbon prepared using ZnCl₂ acid had the highest specific surface area of 546.61 m²/g, while the KOH activating agent surpassed other chemicals in terms of a refined structure and morphology, with the lowest ash content of 10.90%. The surface chemistry study revealed that ZnCl₂ and KOH activated carbon showed phenol and carboxylate groups. Hence, ZnCl₂ acid was suggested as activating agents for micropore carbon, while KOH was favorable to producing a mesopore-activated carbon from sago waste.

Information about the strategic mineral balance, published in 2013, presumed a significant amount of iron sand deposited in Sarmi, Papua, Indonesia. However, the magnetic properties of these iron sands have never been studied. Our preliminary study on the distribution of magnetic susceptibility of iron sand from the Sarmi Coast area has revealed that the iron sand from the Tor River estuary had the highest mass-specific magnetic susceptibility values with an χ_LF average of 3.083 ×10⁻⁵ m³/kg. We extracted the raw sand from the Tor River estuary using a mechanical magnetic extraction method and analyzed the magnetic properties and mineral composition. The magnetic susceptibility values increased significantly with an χ_LF average of 27.496 ×10⁻⁵ m³/kg. The chemical composition acquired from both the X-ray fluorescence and energy dispersive spectroscopy confirmed that the magnetic properties of the extracted sample originated from the high percentage of iron oxide. The hysteresis curve showed high saturation magnetization about 24.7 (emu/g), remanent magnetization of about 6.1 (emu/g) and a low coercive field of about 20 (Oe). The X-ray diffraction patterns identified a magnesioferrite (MgFe₂O₄) mineral structure. This result showed the novelty of iron sand from Sarmi, Papua when compared with that from Java Island.

A phase transformation from insulating brownmillerite SrCoO2.5 to conducting perovskite SrCoO3 through electrochemical oxidation has been demonstrated for thin films of SrCoOx on a SrTiO3(001)...