In this study, NASICON-type Li1+XGaXTi2-X(PO4)3 (x = 0.1, 0.3 and 0.4) solid-state electrolytes for all-solid-state batteries were synthesized through the sol-gel method. In addition, the influence on the ion conductivity of solid-state electrolytes when partially substituted for Ti4+ (0.61Å) site to Ga3+ (0.62Å) of trivalent cations was investigated. The obtained precursor was heat treated at 450 °C, and a single crystalline phase of Li1+XGaXTi2-X(PO4)3 systems was obtained at a calcination temperature above 650 °C. Additionally, the calcinated powders were pelletized and sintered at temperatures from 800 °C to 1,000 °C at 100 °C intervals. The synthesized powder and sintered bodies of Li1+XGaXTi2-X(PO4)3 were characterized using TGDTA, XRD, XPS and FE-SEM. The ionic conduction properties as solid-state electrolytes were investigated by AC impedance. As a result, Li1+XGaXTi2-X(PO4)3 was successfully produced in all cases. However, a GaPO4 impurity was formed due to the high sintering temperatures and high Ga content. The crystallinity of Li1+XGaXTi2-X(PO4)3 increased with the sintering temperature as evidenced by FE-SEM observations, which demonstrated that the edges of the larger cube-shaped grains become sharper with increases in the sintering temperature. In samples with high sintering temperatures at 1,000 °C and high Ga content above 0.3, coarsening of grains occurred. This resulted in the formation of many grain boundaries, leading to low sinterability. These two factors, the impurity and grain boundary, have an enormous impact on the properties of Li1+XGaXTi2-X(PO4)3. The Li1.3Ga0.3 Ti1.7(PO4)3 pellet sintered at 900 °C was denser than those sintered at other conditions, showing the highest total ion conductivity of 7.66 × 10-5 S/cm at room temperature. The total activation energy of Li-ion transport for the Li1.3Ga0.3Ti1.7(PO4)3 solidstate electrolyte was estimated to be as low as 0.36 eV. Although the Li1+XGaXTi2-X(PO4)3 sintered at 1,000 °C had a relatively high apparent density, it had less total ionic conductivity due to an increase in the grain-boundary resistance with coarse grains.

In this investigation, we synthesized a novel quaternary nanocomposite, denoted as RGO-Ba(OH)2/CeO2/TiO2, through a straightforward and cost-effective solid-state synthesis approach. The as-prepared composites underwent a series of comprehensive characterizations, including XRD, FTIR, TGA-DTA, XPS, SEM, EDAX, and TEM analyses, affirming the successful synthesis of a quaternary nanocomposite with well-interconnected nanoparticles, nanorods, and sheet-like structures. Further, our electrochemical performance evaluations demonstrated that the electrochemical capacitance of the RGO-Ba(OH)2/CeO2/ TiO2 nanocomposite achieved an impressive value of 445 F g− 1 at a current density of 1.0 A g− 1, particularly when the mass ratio of CeO2 and TiO2 was maintained at 90:10. Furthermore, the specific capacitance retained a remarkable 65% even after 2000 cycles at a current density of 6 A g− 1 in a 3 mol KOH electrolyte. Comparatively, this outstanding electrochemical performance of the RGO-Ba(OH)2/CeO2/TiO2 (90:10) nanocomposite can be attributed to several factors. These include the favorable electrical conductivity and large specific surface area provided by graphene, TiO2, and Ba(OH)2, the enhanced energy density and extended cycle life resulting from the presence of CeO2, and the synergistic contributions among all four components. Therefore, the RGO-Ba(OH)2/CeO2/TiO2 nanocomposite emerges as a highly promising electrode material for supercapacitors.

MgB2 bulk superconductors are synthesized by the solid state reaction of (MgB4+xMg) precursors withexcessive Mg compositions (x=1.0, 1.4, 2.0 and 2.4). The MgB4 precursors are synthesized using (Mg+B) powders. Thesecondary phases (MgB4 and MgO) present in the synthesized MgB4 are removed by HNO3 leaching. It is found thatthe formation reaction of MgB2 is accelerated when Mg excessive compositions are used. The magnetization curves ofMg1+xB2 samples show that the transition from the normal state to the superconducting state of the Mg excessive sam-ples with x=0.5 and x=0.7 are sharper than that of MgB2. The highest Jc-B curve at 5 K and 20 K is achieved forx=0.5. Further addition of Mg decreases the Jc owing to the formation of more pores in the MgB2 matrix and smallervolume fraction of MgB2.

GdBa2Cu3O7-y(Gd123) powders were synthesized by the solid-state reaction method using Gd2O3 (99.9% purity), BaCO3 (99.75%) and CuO (99.9%) powders. The synthesized Gd123 powder and the Gd123 powder with Gd2O3 addition (Gd1.5Ba2Cu3O7-y(Gd1.5)) were used as raw powders for the fabrication of Gd123 bulk superconductors. The Gd123 and Gd1.5 bulk superconductors were fabricated by sintering or a top-seeded melt growth (TSMG) process. The superconducting transition temperature (Tc,onset) of the sintered Gd123 was 93 K and the transition width was as large as 20 K. The Tc,onset of the TSMG processed Gd123 was 82 K and the transition width was also as large as 12 K. The critical current density (Jc) at 77 K and 0 T of the sintered Gd123 and TSMG processed Gd123 were as low as a few hundreds A/cm2. The addition of 0.25 mole Gd2O3 and 1 wt.% CeO2 to Gd123 enhanced the Tc, Jc and magnetic flux density (H) of the TSMG processed Gd123 sample owing to the formation of the superconducting phase with high flux pinning capability. The Tc of the TSMG processed Gd1.5 was 92 K and the transition width was 1 K. The Jcs at 77 K (0 T and 2 T) were 3.2×104 A/cm2 and 2.5×104 A/cm2, respectively. The H at 77 K of the TSMG-processed Gd1.5 was 1.96 kG, which is 54% of the applied magnetic field (3.45 kG).