Investigation of nanostructure and thermal behavior of zinc-substituted fluorapatite.

The incorporation of various cations such as Zn (2+) into the structure of fluorapatite, Ca 5(PO 4) 3F, is governed by the effectiveness of the cations to substitute for Ca (2+) ions. In this work different concentrations of zinc were used to substitute for calcium. Microscopic characterization was done by observing the nanostructural variations induced by these zinc substitutions and by relating these observations to thermal behavior of the zinc-substituted fluorapatite. Random incorporation of zinc into the fluorapatite structure and the zinc induced amorphization effects oriented in the nanostructure of fluorapatite led to phase impurities of zinc-substituted fluorapatites when the amount of zinc used was greater than 25 mol % of the total cation concentration. It also was observed that the thermal stability of the samples decreased with increasing zinc concentration. Among the zinc-incorporated samples, the most similar chemical and physical properties to the single-phased fluorapatite were identified in the sample containing the lowest amount of zinc (25 mol %). After calcination, however, this sample showed to contain some defects in the atomic arrangement of the nanostructure which led to a thermal instability of the fluorapatite.