EFFECT OF β-CALCIUM ORTHOPHOSPHATE ADDITION ON HIGH- TEMPERATURE PLASTIC DEFORMATION OF HYDROXYAPATITE WITH SUBMICROMETER-SIZED GRAINS

The effect of -calcium orthophosphate (-Ca3(PO4)2:-TCP) addition (1 ~ 20 mass%) on the high-temperature plastic deformation of hydroxyapatite (Ca10(PO4)6(OH)2:HAp) ceramic specimen was examined. The high-density HAp ceramic body with -TCP addition, which was composed of submicrometer-sized grains, was fabricated by pulse-current pressure firing at a temperature between 900 and 1050C for 10 min under a pressure of 50 MPa. The relative densities of HAp ceramics with 1 to 20 mass% -TCP addition fabricated by pulse-current pressure firing at 1000C for 10 min exceeded 99%; the grain sizes increased from 0.2 to 0.3 m with increasing -TCP addition from 0 to 10 mass% and then steeply to 0.9 m with increasing -TCP addition from 10 to 20 mass%. The tensile strain of the HAp specimen with 1 mass% -TCP addition pulse-current pressure fired at 1000C for 10 min achieved a maximum of 390% for a test temperature of 1000C and a strain rate of 1.48  10 -4 s -1 , compared to 364% for the monolithic HAp specimen.