Nucleation of barite (BaSO₄) has broad implications in geological, environmental, and materials sciences. While impurity metals are common, our understanding of how they impact nucleation remains dim. Here, we used classical optical microscopy compared to fast X-ray nanotomography (XnT) to investigate heterogeneous nucleation of barite on silica in situ with Sr²⁺ as an impurity ion. The observed barite nucleation rates were consistent with classical nucleation theory (CNT), where barite crystals displayed a nonuniform size distribution, exhibiting distinct morphologies and incubation periods in Sr-free solutions. While undetectable with optical microscopy, nanotomography revealed that addition of Sr²⁺ enhances nucleation rates driven by the pre-factor in CNT, likely because both adsorbed Ba²⁺ and Sr²⁺ act as precursor sites on which nucleation occurs. Sr²⁺ simultaneously inhibits growth, however, leading to a homogeneous distribution of smaller crystals. This finding will enable an improved predictive understanding of nucleation in natural and synthetic environments.

中文翻译：

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杂质离子Sr2+对重晶石(BaSO4)异相成核和生长的反作用

重晶石 (BaSO ₄ ) 的成核在地质、环境和材料科学中具有广泛的意义。虽然杂质金属很常见，但我们对它们如何影响成核的理解仍然很模糊。在这里，我们使用经典光学显微镜与快速 X 射线纳米断层扫描 (XnT) 进行比较，以 Sr ²⁺作为杂质离子原位研究二氧化硅上重晶石的异质成核。观察到的重晶石成核率与经典成核理论 (CNT) 一致，其中重晶石晶体显示出不均匀的尺寸分布，在无 Sr 溶液中表现出不同的形态和潜伏期。虽然用光学显微镜无法检测到，但纳米断层扫描显示 Sr ^{2+ 的添加}提高了由 CNT 中的前因子驱动的成核速率，这可能是因为吸附的 Ba ²⁺和 Sr ^{2+ 都}作为发生成核的前体位点。然而，Sr ²⁺同时抑制生长，导致较小晶体的均匀分布。这一发现将有助于更好地预测自然和合成环境中的成核。