Characterization of peroxide ions in hydroxyapatite lattice.

The incorporation of peroxide ions was confirmed in the heat treatment of hydroxyapatite (HA) powder under air as well as under oxygen atmosphere, by using X-ray diffraction, Raman, and infrared spectroscopy. Peroxide ions associated with vacancies were sited in the channel of HA lattice along the c-axis through the substitution of a portion of OH radicals. The molecular ions constituted a symmetric vibrator with a stretching vibration active in Raman spectrometry. This vibration was recorded at 750 cm(-1) in the Raman spectra of O(2)(2-)-containing HA samples. The final product was a solid solution of hydroxyl- and peroxide-apatite. However, the existence of peroxide ions in the HA lattice caused the contraction of the unit-cell dimensions of HA materials. In addition, a new hydrogen bond was formed between peroxide ions and adjacent OH radicals by using molecular spectroscopy analysis. During annealing treatment in air, peroxide ions decomposed and the substituted OH radicals re-enter the HA lattice, resulting in the elimination of the structural aberrations caused by the incorporation of peroxide ions. Concentration of the peroxide ions included in HA samples was measured by chemical analysis. Copyright 2000 John Wiley & Sons, Inc.