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Solid solutions between β‐Ca 3 (PO 4 ) 2 and sodium‐containing whitlockite
Author(s) -
Schaeken H. G.,
Driessens F. C. M.,
Verbeeck R. M. H.
Publication year - 1983
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.19835051006
Subject(s) - whitlockite , sodium , pyrophosphate , chemistry , ion , solid solution , analytical chemistry (journal) , mineralogy , nuclear chemistry , inorganic chemistry , materials science , apatite , chromatography , biochemistry , organic chemistry , enzyme
Mixtures of CaHPO 4 , CaCO 3 , and Na 2 CO 3 were heated at 870°C under steam or under dry CO 2 until phase composition and weight were constant. According to chemical analysis and X‐ray diffractometry the stability field of the β‐Ca 3 (PO 4 ) 2 phase is limited by the molar P/Ca ratio of 0.664 ± 0.003 and 0.675 ± 0.010 irrespective of the partial water vapour pressure. A continuous series of solid solutions was found between β‐Ca 3 (PO 4 ) 2 and a new whitlockite with the composition Ca 10 Na(PO 4 ) 7 . The IR spectrum of these solid solutions shows that the point symmetry of the PO 4 groups and their environment increases with increasing sodium content. This is in agreement with data published about the structure of β‐Ca 3 (PO 4 ) 2 and whitlockite. The composition of these solid solutions suggests that Na + ions can replace H + ions in the whitlockite structure. Carbonate and pyrophosphate ions are not incorporated in these whitlockites.