Abstract In this paper, the synthesis of the La3Ba5Cu8O18-δ and Sm3Ba5Cu8O18-δ superconductors using the combustion method is reported for the first time. Besides, a comparison with the solid-state reaction method was performed. The materials were synthesized at 870 °C for 24 h under oxygen flow. Rietveld refinement showed materials with the main crystal phase corresponding to the orthorhombic structure of space-group Pmm2 (25), with purity in the range 51-85%, which had not reported for the RE358 systems. On the other hand, the magnetic measurements under external fields (30 and 100 Oe) confirmed the diamagnetic response associated with the Meissner effect, and Tc values between 24 and 58 K.

The research focused on the hydrothermal synthesis of a material based on a Kesterite structure of Cu2ZnSnS4 (CZTS). For this purpose, the component cations, in concentrations of 1.0 molL-1, were placed in a steel autoclave under different temperatures conditions (200, 220, 240, 260 and 280°C) for 32 h. After, the solids were calcined at 400°C for 2 h. UV-VIS results showed that materials had a strong tendency to absorb in the region of 600-800 nm, with band-gap around 1.54 eV. XRD and Raman confirmed a structure with tetragonal geometry, preferably oriented along the (112) facet, as well as low frequency vibrational and rotational modes typical of CZTS. TEM showed nanometric crystallites (≈41.6 ����). XPS showed the Cu2+, Sn4+, Zn2+ and S4- species in correspondence with its main oxidation states. The electrical analysis, allowed to evaluate the behavior under load conditions, suggesting a potential use these materials for photovoltaic applications.