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The Diffusion of Calcium, Phosphorous, and OD − Ions in Fluorapatite
Author(s) -
den Hartog H.,
Welch D. O.,
Royce B. S. H.
Publication year - 1972
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220530121
Subject(s) - fluorapatite , ion , diffusion , chemistry , analytical chemistry (journal) , perpendicular , calcium , atmospheric temperature range , effective diffusion coefficient , crystallography , apatite , mineralogy , thermodynamics , physics , geometry , medicine , mathematics , organic chemistry , radiology , chromatography , magnetic resonance imaging
Experiments are reported in which the diffusion coefficients for the migration of Ca 2+ , PO 4 3− , and OD − ions have been measured in single crystals of fluorapatite for directions parallel and perpendicular to the crystalline c ‐axis. The measurements have been made over the temperature range between 1000 and 1800 K. Parallel to the c ‐axis the Ca 2+ selfdiffusion coefficient can be empirically represented by D ∥(Ca) = 9.3 × 10 6 exp (−5.64/ kT ) + 3.6 × 10 −3 exp (− 2.46/ kT ) cm 2 s −1 and perpendicular to the c ‐axis by D ⟂(Ca) = = 1.28 × 10 8 exp (−6.0/ kT ) + 7.92 × 10 −8 exp (−1.15/ kT ) cm 2 s −1 . The diffusion coefficient of the phosphate ions is found to be at least two orders of magnitude smaller than that of calcium ions at 1700 K with D ∥ (PO 4 ) = 1.2 × 10 −12 cm 2 s −1 and D ⟂(PO 4 ) = 3.6 × 10 −12 cm 2 s −1 . Preliminary data on the diffusion of OD − ions are also presented. A theoretical model for the calcium diffusion coefficients is discussed. The biological implications of the data are briefly examined.