Vignoles M, Bonel G, Holcomb D W, Young R A
Laboratoire de Physico-Chimie des Solides U.A. C.N.R.S., Toulouse, France.
Calcif Tissue Int. 1988 Jul;43(1):33-40. doi: 10.1007/BF02555165.
It is shown how certain aspects of the composition and structure of carbonated apatites depend strictly on preparation conditions, for example, excess of phosphate or calcium ions in the reaction medium, CO32- concentration, pH, ammonia added or not. Depending on those conditions, either one or the other of the two proposed mechanisms of introduction of carbonate ions into the B sites is dominant. The mechanisms are (1) replacement of a phosphate ion by a carbonate ion with the formation of three vacancies, one in a phosphate oxygen site and one each in the neighboring Ca2+ and OH- sites; and (2) replacement of a phosphate ion by a carbonate accompanied by a hydroxyl ion. Whether mechanism (1) is observed to dominate over mechanism (2), or vice versa, is accounted for by the relative concentrations of the various ions in the reaction medium. The number of vacancies is decreased by the presence of either, or both, excess calcium ions or ammonia in the reaction medium. A structural-chemical mechanism is advanced for the view that, with the smallest CO32- content, the A sites are favored but with increasing carbonate content the B sites become favored and the A-site content becomes less than it is when the total carbonate content is less.
结果表明，碳酸化磷灰石的组成和结构的某些方面严格取决于制备条件，例如反应介质中磷酸根或钙离子的过量情况、CO32-浓度、pH值、是否添加氨。根据这些条件，将碳酸根离子引入B位的两种提出的机制中的一种或另一种占主导地位。这两种机制是：（1）一个碳酸根离子取代一个磷酸根离子，形成三个空位，一个在磷酸根氧位，一个在相邻的Ca2+位，一个在OH-位；（2）一个碳酸根离子取代一个磷酸根离子并伴有一个氢氧根离子。机制（1）是否比机制（2）占主导地位，反之亦然，这由反应介质中各种离子的相对浓度决定。反应介质中存在过量的钙离子或氨中的一种或两种都会减少空位的数量。提出了一种结构化学机制来解释这样一种观点，即当CO32-含量最小时，A位更受青睐，但随着碳酸盐含量的增加，B位更受青睐，且当总碳酸盐含量较低时，A位含量比现在要高。
