We report the synthesis and the characterization of dicalcium phosphate anhydrous (DCPA, CaHPO 4 ) crystals prepared using a hydrothermal process. To prepare an aqueous solution containing Ca 2+ and $$HPO_4^{2-}$$ H P O 4 2 − ion precursors, we dissolved calcium nitrate tetrahydrate and ammonium phosphate dibasic, respectively, in deionized water at room temperature without adding a hydroxide precursor. The pH value was set to about 3.5. The structure and the morphology of the as-grown DCPA crystals were investigated using synchrotron X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy. Disk-shaped microcrystals with rectangular surfaces were observed. The (001) atomic planes of the triclinic monetite structure were aligned along the surface normal direction. We also found that the individual DCPA crystals were single crystals with well-aligned mosaic domains. The full width at half maximum of the φ-scan at off-specular (-1-12) Bragg peaks was approximately 0.061°. This indicated that the atomic positions of the DCPA crystals in the in-plane direction were highly ordered.

中文翻译：

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水热法合成磷酸二钙无水晶体的表征

我们报告了使用水热工艺制备的无水磷酸二钙（DCPA、CaHPO 4 ）晶体的合成和表征。为了制备含有 Ca 2+ 和 $$HPO_4^{2-}$$HPO 4 2 - 离子前体的水溶液，我们分别在室温下将四水硝酸钙和磷酸氢二铵溶解在去离子水中，而不添加氢氧化物前体. pH 值设置为约 3.5。使用同步加速器 X 射线衍射、扫描电子显微镜、能量色散 X 射线光谱和透射电子显微镜研究了生长的 DCPA 晶体的结构和形态。观察到具有矩形表面的盘状微晶。三斜三斜磷灰石结构的 (001) 原子平面沿表面法线方向排列。我们还发现单个 DCPA 晶体是具有排列良好的镶嵌域的单晶。非镜面反射 (-1-12) 布拉格峰的 φ 扫描半峰全宽约为 0.061°。这表明 DCPA 晶体在面内方向的原子位置是高度有序的。