In-situ Raman spectroscopy of amorphous calcium phosphate to crystalline hydroxyapatite transformation

Jessica A. Stammeier, Bettina Purgstaller, Dorothee Hippler, Vasileios Mavromatis, Vasileios Mavromatis, Martin Dietzel

Research output: Contribution to journalArticlepeer-review


The Authors Amorphous calcium phosphate (Ca3(PO4)2xnH2O; n = 3–4.5; ACP) is a precursor phase of the mineral hydroxyapatite (Ca5(PO4)3(OH); HAP) that in natural settings occurs during both authigenic and biogenic mineral formation. In aqueous solutions ACP transforms rapidly to the crystalline phase. The transformation rate is highly dependent on the prevailing physico-chemical conditions, most likely on: Ca & PO4concentration, pH and temperature. In this study, we conducted a calcium phosphate precipitation experiment at 20 °C and pH 9.2, in order to study the temporal evolution of the phosphate mineralogy. We monitored and assessed the transformation process of ACP to crystalline HAP using highly time-resolved in-situ Raman spectroscopy at 100 spectra per hour, in combination with solution chemistry and XRD data. Transformation of ACP to crystalline HAP occurred within 18 h, as it is illustrated in a clear peak shift in Raman spectra from 950 cm−1to 960 cm−1as well as in a sharpening of the 960 cm−1peak. The advantages of this method are: • In-situ Raman spectroscopy facilitates quasi – continuous monitoring of phase transitions.• It is an easy to handle and non-invasive method.
Original languageEnglish
Pages (from-to)1241-1250
Number of pages10
Publication statusPublished - 1 Jan 2018


  • Amorphous calcium phosphate
  • Apatite
  • In-situ monitoring
  • In-situ Raman monitoring
  • Intermediate phase
  • Raman spectroscopy


Dive into the research topics of 'In-situ Raman spectroscopy of amorphous calcium phosphate to crystalline hydroxyapatite transformation'. Together they form a unique fingerprint.

Cite this