Densification and superplasticity of hydroxyapatite ceramics

Fabrication conditions for high-density and fine-grained hydroxyapatite (Ca₁₀ (PO₄)₆(OH)₂: HAp) ceramic were examined; the tensile elongation of HAp ceramic during heating was measured in order to evaluate its possible superplastic behavior. The HAp compact was fired in air at a temperature between 1100 and 1200°C for 5 h. The relative density of HAp compact fired at 1100°C for 5 h showed a maximum (99.2%), whereas the average grain size was as small as 0.56 μm. The tensile elongation of this HAp specimen was tested at a temperature between 940 and 1100°C. The tensile elongations tested at 1050 and 1100°C attained 156 and 157%, respectively; the specimen tested at 1050°C contained a limited number of cavities, whereas the specimen tested at 1100°C was observed to have a large number of cavities.