Rapid one-step preparation of SrZrO3 using Zr4+ gel and SrSO4 ore under alkaline hydrothermal conditions

SrZrO3-structured perovskite particles were prepared under hydrothermal conditions in a KOH (5 M) solution using Zr-gel and SrSO4 mineral precursors. The treatments were con-ducted between 150 and 240 degrees C for different reaction intervals (1-96 h), and the KOH solution volume varied between 7.5 and 30 mL. To evaluate the effect of the Zr-gel precursor, the treat-ments were preliminarily conducted with a coprecipitated pasty Zr-gel (Zr(OH)4 center dot 9.64H2O) and subsequently with a lyophilized Zr-gel Zr(OH)4 powder. Generally, SrZrO3 particles were produced by a single-step reaction following the simultaneous bulk dissolution of the Zr4+ gel precursor and the SrSO4 powder. However, in the preliminary experiments, a dehydra-tion reaction of the pasty Zr-gel preceded the ultimate single-step reaction, resulting in complete SrZrO3 particle formation taking place over a longer interval of 96 h at 240 degrees C. In contrast, when using the dried Zr-gel powder, complete feedstock dissolution occurred more rapidly, producing SrZrO3 particles at 200 degrees C over 48 h. The SrZrO3 particle sizes varied signif-icantly depending on whether the pasty gel or dried powder Zr precursor was used. Particles prepared with the pasty gel exhibited a bimodal size distribution with mean particle sizes of 25 and 65 mu m with pseudocubic and star-shaped cuboidal morphologies, respectively. In contrast, particle growth resulting from the rapid dissolution of solid powder feedstock produced cubic-shaped particles, monomodally distributed with an average particle size of 10 mu m. Furthermore, byproduct (SrCO3) formation occurred predominantly under earlier stages together with SrZrO3 particle irrespective of the 5 M KOH filling volume; however, at a volume of 15 mL spontaneously achieved in situ the SrCO3 dissolution at intermedi-ate stages of reaction. This reaction pathway did not proceed at small (7.5 mL) and large (30 mL) volumes of the alkaline fluid. A kinetic study indicated that the activation energy required to produce the SrZrO3 cubic-shaped particles was low in both cases, i.e., 15.05 and 22.27 kJ mol-1 between the powder and pasty Zr4+ precursors, respectively.(c) 2023 The Author(s). Published by Elsevier Espana, S.L.U. on behalf of SECV. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/ by-nc-nd/4.0/).

Automated summary

SrZrO3-structured perovskite particles were prepared using Zr-gel and SrSO4 precursors in a KOH solution. The particle size varied depending on the type of Zr precursor used. In larger volumes of KOH solution, a byproduct called SrCO3 was produced and spontaneously dissolved at an intermediate stage.