Rare earth carbonates play a significant role in preparing rare earth oxides. This study examines the structure and composition of amorphous dysprosium carbonate (ADC) precursors produced through chemical precipitation. Next, how the amorphous phase changed throughout the hydrothermal process is analyzed. The precursor is identified as the Dy₂(CO₃)₃·xH₂O with spherical morphology (40 nm), as characterized by TEM, XRD, TG-MS, and FT-IR. It was found that ADC will undergo numerous morphological and structural transformations with the progress of the hydrothermal treatment. First, a metastable Dy₂(CO₃)₃·xH₂O is formed, and then a stable crystalline basic dysprosium carbonate Dy(OH)CO₃ is obtained. The self-assembly of amorphous precursor units results in 1D and 3D structures according to the theory of negative ion coordination. The transformation mechanism of dysprosium carbonate follows Ostwald’s rule of stages, where the metastable phase dissolves and recrystallizes to form the stable basic dysprosium carbonate phase.

中文翻译：

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Dy3+–NH4+–CO32– 体系水热过程中碳酸镝的物相和结构演变

稀土碳酸盐在制备稀土氧化物中起着重要作用。本研究考察了通过化学沉淀产生的无定形碳酸镝 (ADC) 前体的结构和组成。接下来，分析了整个水热过程中非晶相是如何变化的。前体被确定为具有球形形态 (40 nm) 的Dy ₂ (CO ₃ ) ₃ · x H _{2 O，如通过 TEM、XRD、TG-MS 和 FT-IR 表征的。}研究发现，随着水热处理的进行，ADC 会发生大量的形态和结构转变。首先，亚稳态 Dy ₂ (CO ₃ ) ₃ · x H形成₂ O，得到稳定的结晶碱式碳酸镝Dy(OH)CO _{3 。}根据负离子配位理论，无定形前体单元的自组装产生 1D 和 3D 结构。碳酸镝的转化机制遵循奥斯特瓦尔德的阶段规则，其中亚稳相溶解并重结晶形成稳定的碱式碳酸镝相。