BaTiO₃ doped with Gd³⁺ (Ba_1-xGd_xTi_1-x/4O₃) was synthesized using the solid-state reaction method with x = 0.001, 0.003, 0.005, 0.01, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, and 0.35 Gd³⁺ (wt. %). The powders were decarbonated at 900 ºC and sintered at 1400 ºC for 8 hours. The tetragonality of the synthesized Gd³⁺-doped BaTiO₃ particles was analyzed. XRD patterns and Raman spectra revealed that the crystal phase of the obtained particles was predominately tetragonal BaTiO₃; the intensity of the Raman bands at 205 cm⁻¹, 265 cm⁻¹, and 304 cm⁻¹ decreased when Gd³⁺ was increased. A secondary phase (Gd₂Ti₂O₇) was found when the Gd³⁺ content was higher than 0.15 wt. %. The capacitance of the sintering pellets was measured at 1 kHz; these values were used to calculate the relative permittivity, the maximum permittivity values were recorded for the samples with x = 0.001, 0.005, and 0.1.

The materials used to conduct kinetic study on the leaching of silver in the S₂O₃²⁻-O₂-Cu²⁺ system were mining residues (tailings) from the Dos Carlos site in the State of Hidalgo, Mexico, which have an estimated concentration of Ag = 71 g∙ton⁻¹. The kinetic study presented in this paper assessed the effects of the following variables on Ag dissolution rate: particle diameter (d₀), temperature (T), copper concentration [Cu²⁺], thiosulfate concentration [S₂O₃²⁻], pH, [OH⁻], stirring rate (RPM), and partial pressure of oxygen (PO₂). Temperature has a favorable effect on the leaching rate of Ag, obtaining an activation energy (Ea) = 43.5 kJ∙mol⁻¹ in a range between 288 K (15 °C) and 328 K (55 °C), which indicates that the dissolution reaction is controlled by the chemical reaction. With a reaction order of n = 0.4, the addition of [Cu²⁺] had a catalytic effect on the leaching rate of silver, as opposed to not adding it. The dissolution rate is dependent on [S₂O₃²⁻] in a range between 0.02 mol·L⁻¹ and 0.06 mol·L⁻¹. Under the studied conditions, variables d₀, [OH⁻] and RPM did not have an effect on the overall rate of silver leaching.

The increasing global demand for copper has driven the search for more efficient and sustainable extraction methods, particularly due to the environmental concerns associated with conventional processes. This study investigated the leaching of copper minerals MC (Cu₂O) and malachite (Cu₂CO₃(OH)₂) using glycine as an organic ligand in an alkaline medium, and evaluated the efficiency of hydrogen peroxide (H₂O₂) and ozone (O₃) as oxidizing agents. Chemical and mineralogical characterization using XRD, XRF, ICP, and SEM confirmed the predominance of MC and malachite, along with secondary phases such as hematite and calcite. Leaching experiments were carried out by varying glycine and oxidant concentrations at pH 10, with a reaction time of 240 min, agitation at 800 min⁻¹, a solution volume of 300 mL, and a mineral sample concentration of 0.33 g·L⁻¹. The results showed that O₃ exhibited low efficiency due to its limited solubility, whereas H₂O₂ achieved dissolution rates of 69.7% for MC in 150 min and 96.3% for MMin just 60 min. The glycine-H₂O₂ system optimized reaction time by 84% compared to conventional methods, emerging as a sustainable alternative due to the low toxicity and biodegradability of glycine.

In this study, the synthesis and structural evolution of pure BaTiO₃ and BaTiO₃ co-doped with La³⁺ and Bi³⁺, produced using the ball milling method and heat treatment, were analyzed. The starting materials included chemically pure precursor powders of BaCO₃, TiO₂, La₂O_3, and Bi₂O₃. Stoichiometric calculations were performed using the Ba_1-3xLa_2xTi_1-3xBi_4xO₃ mechanism with concentrations x = 0.0, 0.0025, 0.0045, 0.006, 0.01, and 0.05 (mol %). The structural and morphological evolution of the samples was characterized by x-ray diffraction (XRD), Rietveld refinement, and high-resolution scanning electron microscopy (HRSEM-EDS). XRD and Rietveld refinement results indicated a tetragonal ferroelectric phase for samples with x ≤ 0.006. As doping levels increased, a peak disappearance was observed, corresponding to a phase transformation from tetragonal to cubic at x = 0.01. Additionally, a cubic secondary phase, BaBiO₃, was detected at x = 0.05, indicating that the maximum solubility of La³⁺ and Bi³⁺ ions in BaTiO₃ was exceeded at this concentration. The concentration x = 0.0025 was found to exhibit the maximum tetragonality among the samples studied, with a value of 1.0087, greater than the tetragonality for pure BaTiO₃, 1.0083. The HRSEM-EDS analysis revealed that for samples with x ≤ 0.006, the microstructure consisted of faceted shape grains with mean grain size in the range of 362.5 nm–488.3 nm. Punctual microanalysis and elemental distribution mapping of the doped samples showed that the grains were composed of Ba, Ti, O, Bi, and La, which were homogeneously distributed, confirming the incorporation of the dopant elements into the BaTiO₃ structure.