I made Hap using sol-gel method by dissolving mussel shell powderin acetic acid and using this calcium solution to make hydroxyapatite via dropwise addition of phosphoric acid till pH=10, oven dry it and calcinated it.
After synthesizing HA, I conducted an XRD analysis of this sample, I found peaks pertaining to standard hydroxyapatite but I also found traces of CaO peaks.
Could you suggest how this happened?
-Thank you
How high was the calcination temperature? Thermal decomposition of calcium acetate can lead to the formation of CaO.
Hydroxyapatite is Ca5(PO4)3OH, which can also be written as 3 Ca3(PO4)2 + Ca(OH)2. If you calcine it at a high enough temperature the Ca(OH)2 component can dehydrate to CaO.
Hydroxylapatite should be stable up to 1300oC (see citation), but the residual calcium acetate will be transformed into calcite, and above about 800oC into CaO.
https://www.mdpi.com/2075-163X/11/12/1310
Article Investigating the optimum conditions for the formation of ca...
Thank you, Sir. I will look into it.
I appreciate your positive responses to my question.
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