Advanced Structural Characterization of BaSn(OH)₃(OOH)(OO) Nanoclusters and BaSnO₃ Nanoparticles

Barium stannate (BaSnO₃) is a cubic perovskite with n-type semiconductor characteristics, high optical transparency and electronic mobility, which is used as an essential component of optoelectronic devices such as solar cells or gas detectors.^1–3 The synthesis and proper crystallization of the perovskite phase requires harsh conditions, such as elevated temperature (&gt;1000 °C), pressure, or are time consuming, which normally result in samples with low control of the particle’s size distribution, stoichiometric and crystallinity.^2–4 A low-temperature synthesis route of BaSnO3 nanoparticles has been reported and can overcome those problems of classical synthesis approaches.¹A crystalline molecular cluster identified as BaSn(OH)₃(OOH)(OO) can be obtained by basic precipitation in a concentrated hydrogen peroxide solution.^1,5 This cluster has cubic structure with replacement of the oxygen atoms of the classical perovskite structure by (OH)^-, (OOH)^- and (OO)^- groups, and can also be converted to the desired BaSnO₃ perovskite phase upon heating at temperatures as low as 300 °C.^1,5 When the molecular cluster is thermally treated it loses ~18% of its total mass by releasing H₂O and O₂ from the decomposition of the (OH)^-_, (OOH)^- and (OO)^- groups which causes a decrease in the parameters of the cubic network due to the contraction of the cell.^1,5 We treated this molecular cluster in vacuum at different temperatures (200-800 °C) and performed structural analyzes of the obtained materials by X-ray Diffraction (XRD) and transmission electron microscopy techniques such as Pair Distribution Function from Electron Diffraction (e-PDF).⁶Our data indicate that the crystalline molecular cluster presents amorphous features with short-range order radius of 1.3 nm. All heat-treated samples resulted in the formation of perovskite BaSnO₃nanoparticles, including the one treated at 200°C, and have short-range order radius of 2.0 nm (200 °C), 2.7 nm (400 °C), 3.6 nm (600 °C) and 4.6 nm (800 °C).<br/><br/>Acknowledgements:<br/>FAPESP Grant Nos. 2023/00906-1 and 2013/07296-2<br/><br/>References:<br/>1. Shin, S. S. <i>et al.</i> Colloidally prepared La-doped BaSnO ₃ electrodes for efficient, photostable perovskite solar cells. <i>Science (1979)</i> <b>356</b>, 167–171 (2017).<br/>2. Lee, W.-J. <i>et al.</i> Transparent Perovskite Barium Stannate with High Electron Mobility and Thermal Stability. <i>Annu Rev Mater Res</i> <b>47</b>, 391–423 (2017).<br/>3. Marikutsa, A. <i>et al.</i> Improved H2S sensitivity of nanosized BaSnO3 obtained by hydrogen peroxide assisted sol-gel processing. <i>J Alloys Compd</i> <b>944</b>, (2023).<br/>4. Azad, A.-M. & Hon, N. C. Characterization of BaSnO3-based ceramics. <i>J Alloys Compd</i> <b>270</b>, 95–106 (1998).<br/>5. Medvedev, A. G. <i>et al.</i> Identification of Barium Hydroxo-Hydroperoxostannate Precursor for Low-Temperature Formation of Perovskite Barium Stannate. <i>Inorg Chem</i> <b>59</b>, 18358–18365 (2020).<br/>6. Souza Junior, J. B. <i>et al.</i> Pair Distribution Function Obtained from Electron Diffraction: An Advanced Real-Space Structural Characterization Tool. <i>Matter</i> <b>4</b>, 441–460 (2021).