Hydroxylapatite with substituted magnesium, zinc, cadmium, and yttrium. I.Structure and microstructure

Hydroxylapatite (HA) was made containing magnesium, zinc, cadmium, and yttr ium. Salts of these cations were added to precipitating HA; the precipitate s were dried and sintered at 1100 degreesC for 1 h. Lattice parameters from X-ray diffraction spectra showed that these elements were incorporated int o the apatite structure at a level of 2% added fraction of calcium in HA an d up to 7% for yttrium. The densities of different substituted apatites wer e close to theoretical for pressed and sintered samples, which is evidence for low bulk porosity. The grain sizes of substituted apatites were smaller than those of pure HA except for cadinium-containing apatite. Surfaces of etched samples showed no second phases, whereas surfaces of unetched sample s showed second phases and higher porosity than etched surfaces. (C) 2001 J ohn Wiley & Sons, Inc.