Sintering of biphasic calcium phosphates.

Biphasic calcium phosphate (BCP) discs were fabricated and then sintered using two different sintering programs to establish whether the phases present could be controlled at low and high sintering temperatures. X-ray diffraction (XRD) was used to establish the phases present after sintering and scanning electron microscopy (SEM) determined the microstructure. Sintering program 1 involved a simple heating and cooling schedule and temperatures of 1100, 1250, 1275 and 1300 degrees C. It produced samples containing an additional alpha-tricalcium phosphate (alpha-TCP) phase at temperatures above 1100 degrees C. The original ratio of hydroxyapatite/beta-tricalcium phosphate (HA/beta-TCP) could not be maintained above this temperature. Sintering program 2 combined the heating and cooling schedules of the first program with a 900 degrees C hold stage to allow alpha-TCP to beta-TCP conversion to take place. At temperatures of 1250 and 1275 degrees C, this program was successful in completely removing the alpha-TCP phase and preserving the HA:beta-TCP ratio. The SEM results show that the surface morphology of the discs was not greatly affected by choice of sintering program.