In this work, a mechanochemical route was proposed for the synthesis of the PrBaMn₂O_5+δ (PMBO) double layered perovskite phase. The mechanochemical reaction between Pr₆O₁₁, BaO₂, and MnO powders with cationic stoichiometric ratios of 1/1/2 for Pr/Ba/Mn was performed using high-energy milling conditions in air. After 150 min of milling, a new phase with perovskite structure and cubic symmetry consistent with the A-site disordered Pr_0.5Ba_0.5MnO₃ phase was formed. When this new phase was subsequently annealed at a high temperature in an inert Ar atmosphere, the layered PrBaMn₂O_5+δ phase was obtained without needing to use a reducing atmosphere. At 1100 °C, the fully reduced layered PrBaMn₂O₅ phase was achieved. A weight gain was observed in the 200–300 °C temperature range when this fully reduced phase was annealed in air, which was consistent with the transformation into the fully oxidized PrBaMn₂O₆ phase. The microstructural characterization by SEM, TEM, and HRTEM ascertained the formation of the intended PrBaMn₂O_5+δ phase. Electrical characterization shows very high electrical conductivity of layered PBMO in a reducing atmosphere and suitable in an oxidizing atmosphere, becoming, therefore, excellent candidates as solid oxide fuel cell (SOFC electrodes).

In this study we demonstrate the synthesis of quaternary semiconductor nanocrystals of stannite Cu₂FeSnS₄/rhodostannite Cu₂FeSn₃S₈ (CFTS) via mechanochemical route using Cu, Fe, Sn and S elements as precursors in one-pot experiments. Methods of X-ray diffraction (XRD), nitrogen adsorption, high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) were applied to characterize properties of the unique nanostructures. Mechanochemical route of synthesis induced new phenomena like explosive character of reaction, where three stages could be identified and the formation of nanostructures 5–10 nm in size. By using XPS method, Cu(I), Fe(II), Sn(IV) and S(-II) species were identified on the surface of CFTS. The value of optical band gap 1.27 eV is optimal for semiconductors applicable as absorbers in solar cells. The significant photocatalytic activity of the CFTS nanocrystals was also evidenced. The obtained results confirm the excellent properties of the quaternary semiconductor nanocrystals synthesized from earth-abundant elements.

Copper, antimony and sulfur in elemental form were applied for one-pot solid-state mechanochemical synthesis of skinnerite (Cu₃SbS₃) in a laboratory mill and an industrial mill. This synthesis was completed after 30 min of milling in the laboratory mill and 120 min in the industrial mill, as corroborated by X-ray diffraction. XRD analysis confirmed the presence of pure monoclinic skinnerite prepared in the laboratory mill and around 76% monoclinic skinnerite, with the secondary phases famatinite (Cu₃SbS₄; 15%), and tetrahedrite (Cu_11.4Sb₄S₁₃; 8%), synthesized in the industrial mill. The nanocrystals were agglomerated into micrometer-sized grains in both cases. Both samples were nanocrystalline, as was confirmed with HRTEM. The optical band gap of the Cu₃SbS₃ prepared in the laboratory mill was determined to be 1.7 eV with UV–Vis spectroscopy. Photocurrent responses verified with I–V measurements under dark and light illumination and Cu₃SbS₃ nanocrystals showed ~45% enhancement of the photoresponsive current at a forward voltage of 0.6 V. The optical and optoelectrical properties of the skinnerite (Cu₃SbS₃) prepared via laboratory milling are interesting for photovoltaic applications.

Ternary wittichenite Cu₃BiS₃ nanocrystals were prepared mechanochemically using a planetary ball mill from elemental copper, bismuth and sulfur in a stoichiometric ratio in only 5 min. The orthorhombic wittichenite Cu₃BiS₃ was nanocrystalline with an approximate crystallite size of 38 nm ± 9 nm, as confirmed by Rietveld refinement. The nanocrystalline character of orthorhombic Cu₃BiS₃ was also proven by transmission electron microscopy. The measured Raman spectrum confirmed the formation of pure wittichenite Cu₃BiS₃. The morphology characterization demonstrated the homogeneity of the sample. The value of the specific surface area for pure mechanochemically prepared Cu₃BiS₃ after 5 min was 2.7 m²g⁻¹. The optical properties were investigated using UV–Vis absorption and micro-photoluminescence spectroscopy. From the absorption UV–Vis spectrum, the value of the bandgap energy was determined to be 1.52 eV, which creates an assumption for the use of wittichenite Cu₃BiS₃ in photovoltaic applications. The optoelectrical properties of the prepared Cu₃BiS₃ nanocrystals were verified by current–voltage measurements in the dark and under white light illumination. The photocurrent increased by 26% compared to the current in the dark at a voltage of 1 V. The achieved results confirmed a very fast and efficient way of synthesizing a ternary wittichenite Cu₃BiS₃, which can be used for applications in solar cells.

In this study, we report the optoelectric and thermoelectric properties of famatinite Cu₃SbS₄ that was mechanochemically synthesized in a planetary mill from powder elements for 120 min in an inert atmosphere. The tetragonal famatinite Cu₃SbS₄ was nanocrystalline with a crystallite size of 14 nm, as endorsed by Rietveld refinement. High-resolution transmission electron microscopy showed several crystallites in the range of 20–50 nm. Raman spectroscopy proved the purity of the synthesized famatinite Cu₃SbS₄ and chemical-state characterization performed by X-ray photoelectron spectroscopy confirmed that the prepared sample was pure. The Cu¹⁺, Sb⁵⁺, and S²⁻ oxidation states in Cu₃SbS₄ sample were approved. The morphology characterization showed homogeneity of the prepared sample. The photoresponse of Cu₃SbS₄ was confirmed from I–V measurements in the dark and under illumination. The photocurrent increase reached 20% compared to the current in the dark at a voltage of 5 V. The achieved results confirm that synthesized famatinite Cu₃SbS₄ can be applied as a suitable absorbent material in solar cells. The performed thermoelectric measurements revealed a figure of merit ZT of 0.05 at 600 K.