Preparation of barium monohydrofluoride BaF2·HF from nitrate aqueous solutions

• Aqueous Ba(NO3)2 forms with HF (>0.7 wt.%) BaF2·HF instead of the expected BaF2.
• Size of BaF2·HF crystals depend on concentrations, ratios, order of addition of starting materials.
• Maximal yield of BaF2·HF was obtained with the use of 0.8 M Ba(NO3)2 and 2 equiv. 26 M HF.
• BaF2·HF is an excellent precursor for optical and scintillator fluoride ceramics.

Barium ions react with HF in aqueous media, forming BaF2·HF for >0.7 wt.% aqueous HF instead of the expected BaF2 precipitates. Optimal yields of BaF2·HF have been obtained with the use of concentrated Ba(NO3)2 (0.8 М) and HF (26.0 М) aqueous solutions, using more than 2 equiv. of the latter. The composition, morphology and particle size of the formed precipitates are dependent upon the synthetic conditions, such as concentrations of starting materials, their stoichiometry and order of addition. BaF2·HF is an excellent precursor for the preparation of optical fluoride ceramics having high transparency in the 0.3–12 μm range, and scintillator ceramics (e.g., BaF2 or BaF2:Ce3+) as well.

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