Preparation and structure of calcium hydroxyapatite substituted with light rare earth ions

The present study synthesized five types of hydroxyapatite (Hap) particles containing light rare earth ions (Ln(3+): La3+, Ce3+, Pr3+, Nd3+ and Sm3+) and Ca2+ ions from aqueous solutions with different Ln/(Ln + Ca) atomic ratios ([X-Ln]) ranging from 0 to 0.15. The crystal phases of the products and their inner and surface structures were investigated by various means. Ln(3+) ions were incorporated into the CaHap crystals and formed rare earth metal-calcium hydroxyapatite (LnCaHap) solid solutions at [X-Ln] <= 0.01-0.03. A mixture of LnCaHap and LnPO(4) was formed in each Ln system at [X-Ln] > 0.01-0.03. Ln(3+) ions strongly affected the structure of the particles, although only a small quantity of Ln(3+) ions was incorporated into the Hap crystals. With increasing [X-Ln], the prepared particles first became longer and then became smaller. The crystallinity of the particles was altered, corresponding with the variation of their size. UV-vis measurements revealed that Ce-contained Hap exhibits strong UV absorption under 400 nm. (C) 2011 Elsevier B.V. All rights reserved.