New Approach to the β→α Polymorphic Transformation in Magnesium‐Substituted Tricalcium Phosphate and its Practical Implications

Abstract

The transformation β→α in Mg‐substituted Ca 3 (PO 4 ) 2 was studied. The results obtained showed that, contrary to common belief, there is, in the system Mg 3 (PO 4 ) 2 –Ca 3 (PO 4 ) 2 , a binary phase field where β+α‐Ca 3 (PO 4 ) 2 solid solutions coexist. This binary field lies between the single‐phase fields of β‐ and α‐Ca 3 (PO 4 ) 2 solid solution in the Ca 3 (PO 4 ) 2 ‐rich zone of the mentioned system. In the light of the results and the Palatnik–Landau's Contact Rule of Phase Regions, a corrected phase equilibrium diagram has been proposed. The practical implications of these findings with regard to the synthesis of pure α‐ and β‐ Mg‐substituted Ca 3 (PO 4 ) 2 powders and to the sintering of related bioceramics with improved mechanical properties are pointed out.