Preparation and structure of carbonated calcium hydroxyapatite substituted with heavy rare earth ions

Calcium hydroxyapatite (CaHap) particles substituted five types of heavy rare earth ions (Ln: Y3+, Gd3+, Dy3+, Er3+ and Yb3+) were synthesized using a precipitation method and characterized using various means. These Ln ions strongly affected the crystal phases and the structures of the products. With increasing Ln/(Ln + Ca) in the starting solution ([XLn]), the length and the crystallinity of the particles first increased and then decreased. The rare earth metal-calcium hydroxyapatite (LnCaHap) solid solution particles were obtained at [XY] ≤ 0.10 for substituting Y system and at [XLn] ≤ 0.01–0.03 for substituting the other Ln systems. LnPO4 was mixed with LnCaHap at higher [XLn] for all Ln systems. A series of yttrium-calcium hydroxyapatite (YCaHap) solid solutions with [XY] = 0–0.10 were investigated using XRD, TEM, ICP-AES, IR and TG–DTA in detail.

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► LnCaHap solid solution particles were prepared using five types of heavy rare earth ions by a precipitation method.
► The length and the crystallinity of the LnCaHap particles first increased and then decreased with increasing Ln3+ contents.
► A series of YCaHap solid solution particles formed with Y/(Y + Ca) = 0–0.10 were investigated using various methods in detail.