Synthesis and characterization of the copper doped Ca-La apatites

• New colored copper-doped apatite-type materials were synthesized.
• Positions of the La and Cu ions in the crystal lattice were determined.
• Relationships between crystal structure and spectral characteristics were described.
• Specific chromophore centres were characterized.

Copper-containing Ca-La hydroxyapatites (HAPs) with chemical compositions Ca10-xLax(PO4)6O2H1.5-x-y-δCuy (x = 0–1.79; y = 0–0.57) were synthesized by solid state reaction. Structural parameters and atomic positions were refined using the Rietveld method in space group P63/m. It was found that La3+ ions occupied the Ca(2) position only and copper ions were located mainly inside the hexagonal channel. In contrast to known red-violet copper-doped Ca-apatites, the copper-doped Ca-La apatites exhibited lighter colors varying from pink to pale yellow and blue-grey tints. Chromophores in the compounds were characterized by diffuse reflectance spectroscopy, colorimetry, and resonant Raman spectroscopy.