Structural and morphological evolution of biogenic hydroxyapatite: Effects of heating and cooling treatment

Abstract

Despite extensive research, many aspects of biogenic hydroxyapatite (BHA) structural changes during heating remain unresolved. This work aims to understand how heating and cooling affect the growth of BHA crystallites obtained from porcine bone through an in-situ study. Wavelength-dispersive X-ray fluorescence of BHA has revealed the presence of trace elements such as Si, Al, Fe, Mg, and K. These elements serve as substitutional defects within the BHA structure. Vibrational analysis using infrared spectroscopy helped to verify the removal of the organic phase by combustion. In situ high-temperature X-ray diffraction and Rietveld refinement were used to analyze the changes in BHA crystallite size, lattice parameters, and microstrain. High-resolution micrographics confirmed the simulation of crystal habit using family planes (002), (111), (100), and (110) and validated the removal of organic material. Remarkably, the crystallite size increased dramatically after organic debris removal and coalescence events, while it remained constant before coalescence temperature.