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 ([X-Ln]), 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 [X-Y] <= 0.10 for substituting Y system and at [X-Ln] <= 0.01-0.03 for substituting the other Ln systems. LnPO(4) was mixed with LnCaHap at higher [X-Ln] for all Ln systems. A series of yttrium-calcium hydroxyapatite (YCaHap) solid solutions with [X-Y] = 0-0.10 were investigated using XRD, TEM, ICP-AES, IR and TG-DTA in detail. (C) 2012 Elsevier Ltd. All rights reserved.