Effect of sintering time on the microstructure and properties of inorganic polyphosphate bioceramics

Sintering is an important step in the fabrication process of ceramic bodies, which can significantly affect the microstructure and properties of materials. In this article, calcium based inorganic polyphosphate (CPP) bioceramics were synthesized by gravity sintering. Effects of the sintering time (30 minutes, 1 hour, 3 hours and 5 hours) on the microstructure, physicochemical degradation and mechanical property were investigated. It was found that all prepared CPP samples for various sintering times showed a β-CPP phase at the temperature of 800oC. The sample morphology changed to more compact with extending the sintering time from 30 minutes to 5 hours. Moreover, the grain size increased with the increase of sintering time, from 1.59 μm for 30 minutes to 3.40 μm for 5 hours. The in vitro degradation test revealed that the degradation velocity had an inverse relationship with the sintering time. The CPP samples sintering for 30 minutes showed the fastest degradation, while CPP sintering for 5 hours was the slowest one. Compression test results showed that longer sintering times led to improved mechanical properties.