Effect of copper inclusion on lattice parameters, stoichiometry, and thermal phase transition of hydroxyapatite

Cu inclusion in hydroxyapatite (HA) can provide newfound advantages. Still, fundamental properties of these materials are understudied. Motivated by this, a series of Cu-containing HA (CuHA) was synthesized via aqueous co-precipitation. Pawley fitting of X-ray powder diffraction (XRD) patterns revealed a dilation of lattice parameters with increasing Cu content, causing a maximum expansion of unit cell volume from 518.2(7) to 528.0(4) Å3. Functional group presence and stoichiometry were investigated using spectroscopic characterization and X-ray fluorescence (XRF), respectively. High-temperature in-situ XRD followed by quantitative phase identification assessed the thermal transition to β-tricalcium phosphate (β-TCP). As Cu target incorporation increased from 0 to 5 mol% (actual 0–1.96 mol%), there was an observable increase in stoichiometry, carbonate removal, and resistance to thermal phase transition. This work also emphasizes the tunability of certain properties through Ca deprivation in the synthesis method. Some key structure–property relationships are identified to build on current understanding of CuHA and its complexities.