Abstract

The BiAl₃(PO₄)₂(OH)₆ compound with a waylandite structure has been synthesized for the first time under hydrothermal conditions at 200°С and a pressure of 7 MPa. It has been shown that the compound forms through the formation of an intermediate crystalline phase—trigonal BiPO₄—and an amorphous phase of composition 0.5[3Al₂O₃ ⋅ 2P₂O₅ ⋅ 6H₂O]. According to SEM data, particles resembling in morphology particles of the phase with a waylandite structure are detected after 6 h of synthesis. The formation of BiAl₃(PO₄)₂(OH)₆ in amounts distinguishable by X-ray diffraction is fixed after 12 h and almost completely ends after 48 h of hydrothermal treatment of the suspension of precursors. The formation of waylandite is confirmed by SEM and IR spectroscopy. The structure of BiAl₃(PO₄)₂(OH)₆ was refined by the Rietveld method from powder X-ray diffraction data (space group \(R\bar {3}m\) (166) in hexagonal axes, unit cell parameters: a = 6.99608(5) Å, c = 16.1495(4) Å). Refinement gives the filling factors of unity within the standard deviation for the positions of atoms heavier than oxygen. The measured pycnometric density of the sample (4.01(8) g/cm³) is slightly lower than the density calculated from the results of structure refinement (4.235(2) g/cm³).

中文翻译：

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水热条件下具有Waylandite结构的BiAl3(PO4)2(OH)6化合物的形成

摘要

首次在200°С和7 MPa的水热条件下合成了具有Waylandite结构的BiAl ₃ (PO ₄ ) ₂ (OH) _{6化合物。}已经表明，该化合物通过形成中间结晶相 - 三角 BiPO ₄ - 和组成为 0.5[3Al ₂ O ₃ ∙ 2P ₂ O ₅ ∙ 6H ₂ O] 的非晶相形成。根据 SEM 数据，在合成 6 小时后检测到形态上类似于具有硅钙石结构的相的颗粒。BiAl ₃ (PO ₄ ) _2的形成(OH) ₆可通过 X 射线衍射区分的量在 12 小时后固定，并在前体悬浮液的水热处理 48 小时后几乎完全结束。通过 SEM 和 IR 光谱证实了韦兰石的形成。BiAl ₃ (PO ₄ ) ₂ (OH) ₆的结构通过 Rietveld 方法从粉末 X 射线衍射数据 (空间群\(R\bar {3}m\) (166) 在六角轴，晶胞参数：a = 6.99608(5) Å, c= 16.1495(4) Å)。对于比氧重的原子的位置，细化给出了标准偏差内的统一填充因子。样品的测得比重密度（4.01(8) g/cm ³）略低于根据结构细化结果计算的密度（4.235(2) g/cm ³）。